El efecto anti-hipertensivo de angiotensina-(1-9) es mediado por aumento temprano de la diuresis y natriuresis / Cardiac arrest associated to intramural hematoma of the anterior descending coronary artery

Introducción: Angiotensina (Ang)-(1-9) posee propiedades anti-hipertensivas y efecto protector a nivel cardiovascular en ratas hipertensas. Sin embargo, se desconoce si estos efectos están asociados a un mecanismo de desbalance de sodio a nivel renal. Objetivo: Determinar si el efecto anti-hipertensivo de Ang-(1-9) está asociado a un mecanismo diurético-na-triurético. Método: Ratas macho Sprague Dawley (200 ± 10g) fueron aleatorizadas para recibir Ang II (400 ng/kgmin) vía bomba osmótica. Como control se utilizaron ratas con operación sham (n=18). Después de 2 semanas desde la instalación de bomba, las ratas Sham e hipertensas fueron randomizadas para recibir vehículo (n=10), Ang-(1-9) (602 ng/kg/min, n=17) o una co-administración de Ang-(1-9) y A779 (100 ng kg-1min-1, n=7 bloqueador del receptor MAS) por 2 semanas. Resultados: Se determinó la presión arterial sistólica (PAS), masa ventricular relativa (MVR), área y perímetro de los cardiomiocitos (AC y PC) y la fracción volumétrica de colágeno total (FVCT). Para evaluar la diuresis y natriuresis se utilizaron ratas normotensas que fueron randomizadas para recibir vehículo (n=8) o Ang-(1-9) (600 ngKg-1min-1, n=8) por 6 días. Se observó un incremento significativo(p<0.05) de PAS (33%), MVR (17%), AC (64%), PC (20%), FVCT (46%). La administración crónica de Ang-(1-9) disminuyó PAS (20%), MVR (13 %), AC (35%), PC (20%) y FVCT (20%). Estos efectos no fueron mediados por el receptor MAS. Al comparar las ratas normotensas tratadas con vehículo o Ang-(1-9), se observó un aumento significativo de la diuresis y natriuresis en los días 2 y 3 en los animales con infusión de Ang-(1-9). Conclusión: Ang-(1-9) reduce la hipertensión y el remodelamiento cardíaco en ratas hipertensas. En animales normotensos se demostró que el tratamiento con Ang-(1-9)-induce diuresis y natriuresis. Este es el primer reporte que señala que el efecto de Ang-(1-9) está asociado a una regulación del sodio a nivel renal.

Background: Angiotensin-(1-9) has anti-hypertensive properties and protective cardiovascular effect in hypertensive rats. However, it is unknown whether its effects are related to a kidney mechanism to balance sodium. Aim: To determine if the anti-hypertensive effect of Ang-(1-9) is associated to a diuretic-natriuretic mechanism. Method: Sprague Dawley male rats (200±10 grs) were randomized to receive Angiotensin II by osmotic pump (400 ng/kg/min). Sham operated rats were utilized as control (n=18). Two weeks after pump setting, Sham rats with hypertension were randomized to receive placebo (n=10), Ang-(1-9)(602 ng/kg/min, n=17) or Ang-(1-9) plus A779 (Ang-(1-7) Receptor Mas blocker, 100ng/kg-1min-1, n=7) co-administration for two weeks. Arterial systolic pressure (PAS), ventricular relative mass (MVR), cardiomyocytes area and perimeter (AC and PC) and total collagen volume fraction (FVCT) were measured. Normotensive rats were utilized to evaluate diuresis and natriuresis which were randomized to receive placebo (n=8) or Ang-(1-9) (600ng/kg-1/min-1, n=8) for six days. Results: It was observed a significant rise (p<0.05) of PAS (33%), MVR (17%), AC (64%), PC (26%), FVCT (46%) was observed. Chronic administration of Ang-(1-9) reduced PAS (20%), MVR (13%), AC (35%), PC (20%) and FCVT (20%). All those effects were not mediated by Mas receptor. A significant raise was observed of diuresis and natriuresis at the second and third day of treatment in rats receiving Ang-(1-9) in comparison with normotensive rats treated with placebo. Conclusion: Ang-(1-9) reduces hypertension and cardiac remodeling in hypertensive rats. Ang-(1-9) induces natriuresis and diuresis in normotensive rats. This is the first report showing that Ang-(1-9) is associated to sodium balance in the kidney.

Efecto diurético agudo de los extractos etanólico y acuoso de Ceratopteris pteridoides (Hook) en ratas normales / Acute diuretic effect of ethanolic and aqueous extracts of Ceratopteris pteridoides (Hook) in normal rats

Introducción. Ceratopteris pteridoides es un helecho semiacuático de la familia Parkeriacea, ampliamente utilizado en la medicina popular colombiana como diurético y colelitiásico, sobre el cual no existen reportes científicos que avalen su uso popular como diurético. Objetivo. Evaluar el efecto diurético agudo en dosis única y dosis repetidas a corto plazo, de los extractos etanólico y acuoso de C. pteridoides en un modelo in vivo . Materiales y métodos. El extracto etanólico total fue obtenido por maceración de la planta entera de C. pteridoides con etanol y el extracto acuoso fue obtenido por decocción a 60 °C por 15 minutos. Ambos extractos se sometieron a análisis fitoquímico preliminar y estudio histológico posterior a la administración de los extractos durante ocho días consecutivos (1.000 mg/kg). El efecto diurético se evaluó en ratas Wistar, tratadas con los extractos (500 mg/kg), en forma aguda y en dosis repetidas a corto plazo, cuantificando la eliminación de agua y la excreción renal de sodio y potasio por espectrofotometría de absorción atómica y, de cloruros, por titulación mercurimétrica. Resultados. En el modelo agudo, ambos extractos mostraron un significativo efecto diurético y de excreción renal de sodio y potasio en comparación con el control, mientras que con la administración en dosis repetidas a corto plazo mostraron efecto diurético sin eliminación de electrolitos. El estudio histopatológico no sugirió efectos tóxicos hepáticos o renales. Conclusión. Los resultados demuestran la actividad diurética de C. pteridoides y sustentan el uso popular dado a esta planta como diurético en la costa norte colombiana. Se requieren estudios posteriores que permitan aislar e identificar los compuestos responsables de la actividad y los mecanismos de acción involucrados.

Introduction. Ceratopteris pteridoides is a semiaquatic fern of the Parkeriacea family, widely used in the Colombian folk medicine as a diuretic and cholelithiasic, of which there are no scientific reports that validate its popular use. Objective. To evaluate the acute and short-term repeated-dose diuretic effect of the ethanolic and aqueous extracts of C. pteridoides in an in vivo model. Materials and methods. The total ethanolic extract was obtained by maceration of the whole plant of C. pteridoides with ethanol and the aqueous extract by decoction at 60°C for 15 minutes. Both extracts were evaluated in preliminary phytochemical analysis and histological studies after the administration of the extracts for 8 consecutive days (1000 mg/Kg). The diuretic effect was evaluated using Wistar rats treated with the extracts (500 mg/Kg), using an acute and a short-term repeated-dose model, and quantifying water elimination, sodium and potassium excretion by atomic absorption spectrophotometry, and chloride excretion by mercurimetric titration. Results. In the acute model both extracts showed significant diuretic, natriuretic, and kaliuretic effect compared to the control group. Whereas, a short-term repeated-dose administration showed a diuretic effect without elimination of electrolytes. The histopathologic study did not suggest a toxic effect in liver or kidney. Conclusion. The results represent evidence of the diuretic activity of C. pteridoides and give support the popular use given to this plant in the north coast of Colombia. Further studies are required to isolate and identify the compounds responsible for the activity and the mechanism of action involved.

In vivo and in vitro anti-natriuretic activity of twigs fraction from Dorstenia picta: a possible mechanism

The present study examine the in vivo effects of Dorstenia Picta [D. picta] on urinary volume and sodium excretion in streptozotocin-induced diabetic rats, and determine a possible mechanism by which the extract increased sodium transport in A6 cells monolayers. Administration of the plant extract at the dose of 150 mg/kg during two weeks decreased urinary volume and sodium excretion. In vitro study showed that, apical application of the plant extract at the dose of 100 micro g/mL does not significantly increase sodium transport, whereas basolateral administration provoked a significant [P<0.05] increase of sodium transport in a concentration-dependent manner. The plant extract increases the sodium transport by 69.93% versus 55.41% for insulin and 78.44% for adenosine after 30 min. Preincubation of A6 cells monolayers with inhibitor of all adenosine receptors completely suppressed adenosine and plant extract stimulated sodium transport. Interesting is that, the A1 inhibitor receptor [DPCPX], at 100 nM completely abolished the effect of plant extract. The plant extract increased sodium transport by increase PI3-kinase activity and this effect is strongly inhibited by LY-294002. These data also suggest that, the twigs methanol fraction from Dorstenia picta increase sodium transport via PI 3-kinase pathway and requires A1 adenosine receptor

Patterns of renal dopamine release to regulate diuresis and natriuresis during volume expansion: Role of renal monoamine-oxidase / Perfiles de secreción de dopamina renal en la expansión de volumen para regular diuresis y natriuresis: Rol de la monoaminoxidasa renal

Diuretic and natriuretic effects of renal dopamine (DA) are well established. However, in volume expansion the pattern of renal DA release into urine (U DA V) and the role of enzymes involved in DA synthesis/degradation have not yet been defined. The objective was to determine the pattern of U DA V during volume expansion and to characterize the involvement of monoamine-oxidase (MAO) and aromatic amino-acid decarboxylase (AADC) in this response. In this study male Wistar rats were expanded with NaCl 0.9% at a rate of 5% BWt per hour. At the beginning of expansion three groups received a single drug injection as follows: C (vehicle, Control), IMAO (MAO inhibitor Pargyline, 20 mg/kg BWt, i.v.) and BNZ (AADC inhibitor Benserazide, 25 mg/kg BWt, i.v.). Results revealed that in C rats U DA V (ng/30 min/100g BWt) increased in the first 30 min expansion from 11.5 ± 1.20 to 21.8 ± 3.10 (p < 0.05) and decreased thereafter. IMAO showed a similar pattern but significantly higher than C at 30 min expansion (32.5 ± 2.20, p < 0.05). IMAO greatly reduced MAO activity from 8.29 ± 0.35 to 1.1 ± 0.03 nmol/mg tissue/hour and significantly increased diuresis and natriuresis over controls. BNZ abolished the early U DA V peak to 3.2±0.72 (p < 0.01) and though, U DA V increased over C after 60 min expansion, natriuresis and diuresis were diminished by BNZ treatment. Results indicate that an increment in renal DA release into urine occurs early in expansion and in a peak-shaped way. In this response MAO plays a predominant role.

La dopamina (DA) intrarrenal ejerce efectos diuréticos y natriuréticos. Sin embargo, en los estado de expansión de volumen aún no está bien definido el patrón de liberación de dopamina renal hacia la orina y si cumplen un rol las enzimas involucradas en la síntesis o degradación de la amina. El objetivo del presente trabajo fue determinar el patrón de excreción urinaria de DA (U DA V) durante la expansión de volumen, caracterizando la participación de las enzimas monoaminooxidasa (MAO) y decarboxilasa de aminoácidos aromáticos (AADC) en esta respuesta. Para ello ratas Wistar macho fueron expandidas de volumen con NaCl 0.9% al 5% del peso corporal por hora durante dos horas y divididas en tres grupos, los que al comienzo de la expansión recibieron: C (vehículo, Control), IMAO (Pargilina, inhibidor de MAO, 20 mg/kg PC, i.v.) y BNZ (Benserazida, inhibidor de AADC, 25 mg/kg PC, i.v.). Se observó que en C la U DA V (ng/30min/100gPC) aumentó durante los primeros 30 minutos de expansión de 11.5 ± 1.20 a 21.8 ± 3.10 (p < 0.05), disminuyendo posteriormente. IMAO mostró un patrón de liberación similar pero significativamente mayor que C a los 30 min de expansión (32.5 ± 2.20, p < 0.05). En este grupo la actividad de MAO disminuyó de 8.29 ± 0.35 a 1.1 ± 0.03 nmol/mg tejido/hora y aumentaron la diuresis y natriuresis por sobre los controles. En BNZ, el pico de U DA V observado a los 30 min de la expansión disminuyó a 3.2 ± 0.72 (p < 0.01), aunque luego de 60 minutos fue mayor que en C. BNZ disminuyó tanto la diuresis como la natriuresis. Podemos concluir que al comienzo de la expansión de volumen se produce un pico de excreción de dopamina renal hacia la orina. La enzima MAO juega un rol fundamental en esta respuesta.

Consequences of cerebroventricular insulin injection on renal sodium handling in rats: effect of inhibition of central nitric oxide synthase

In the present study, we investigated the effects of acute intracerebroventricular (icv) insulin administration on central mechanisms regulating urinary sodium excretion in simultaneously centrally NG-nitro-L-arginine methylester (L-NAME)-injected unanesthetized rats. Male Wistar-Hannover rats were randomly assigned to one of five groups: a) icv 0.15 M NaCl-injected rats (control, N = 10), b) icv dose-response (1.26, 12.6 and 126 ng/3 µL) insulin-injected rats (N = 10), c) rats icv injected with 60 µg L-NAME in combination with NaCl (N = 10) or d) with insulin (N = 10), and e) subcutaneously insulin-injected rats (N = 5). Centrally administered insulin produced an increase in urinary output of sodium (NaCl: 855.6 ± 85.1 Ä percent/min; 126 ng insulin: 2055 ± 310.6 Ä percent/min; P = 0.005) and potassium (NaCl: 460.4 ± 100 Ä percent/min; 126 ng insulin: 669.2 ± 60.8 Ä percent/min; P = 0.025). The urinary sodium excretion response to icv 126 ng insulin microinjection was significantly attenuated by combined administration of L-NAME (126 ng insulin: 1935 ± 258.3 Ä percent/min; L-NAME + 126 ng insulin: 582.3 ± 69.6 Ä percent/min; P = 0.01). Insulin-induced natriuresis occurred by increasing post-proximal sodium excretion, despite an unchanged glomerular filtration rate. Although the rationale for decreased urinary sodium excretion induced by combined icv L-NAME and insulin administration is unknown, it is tempting to suggest that perhaps one of the efferent signals triggered by insulin in the CNS may be nitrergic in nature.

BTCI enhances guanylin-induced natriuresis and promotes renal glomerular and tubular effects

Guanylin and uroguanylin are small cysteine-rich peptides involved in the regulation of fluid and electrolyte homeostasis through binding and activation of guanylyl cyclases signaling molecules expressed in intestine and kidney. Guanylin is less potent than uroguanylin as a natriuretic agent and is degraded in vitro by chymotrypsin due to unique structural features in the bioactive moiety of the peptide. Thus, the aim of this study was to verify whether or not guanylin is degraded by chymotrypsin-like proteases present in the kidney brush-border membranes. The isolated perfused rat kidney assay was used in this regard. Guanylin (0.2 µM) induced no changes in kidney function. However, when pretreated by the black-eyed pea trypsin and chymotrypsin inhibitor (BTCI - 1.0 µM; guanylin - 0.2 µM) it promoted increases in urine flow (deltaUF of 0.25 ± 0.09 mL.g-1/min, P < 0.05) and Na+ excretion ( percent delta ENa+ of 18.20 ± 2.17, P < 0.05). BTCI (1.0 µM) also increased percentENa+ (from 22.8 ± 1.30 to 34.4 ± 3.48, P < 0.05, 90 minutes). Furthermore, BTCI (3.0 µM) induced increases in glomerular filtration rate (GFR; from 0.96 ± 0.02 to 1.28 0.02 mL.g-1/min, P < 0.05, 60 minutes). The present paper strongly suggests that chymotrypsin-like proteases play a role in renal metabolism of guanylin and describes for the first time renal effects induced by a member of the Bowman-Birk family of protease inhibitors.

Guanilina e uroguanilina são peptídeos pequenos, ricos em cisteína, envolvidos na regulação da homeostase de fluidos e eletrólitos através da ligação e ativação da guanilato ciclase expressa no intestino e nos rins. A guanilina é menos potente do que a uroguanilina como agente natriurético e é degradada in vitro pela quimiotripsina devido a características estruturais únicas no domínio bioativo do peptídeo. Portanto o objetivo deste trabalho foi verificar se a guanilina é degradada por proteases tipo quimiotripsina, presentes na membrana da borda em escova dos rins. Para esta investigação, foi usado o modelo do rim isolado de rato perfundido. A Guanilina (0,2 µM) não induziu mudanças na função renal. Entretanto, quando pré-tratada com inibidor de tripsina e de quimiotripsina de black-eyed pea (BTCI - 1,0 µM; guanilina - 0,2 µM) promoveu um aumento no fluxo urinário (deltaUF de 0,25 ± 0,09 mL.g-1/min, P < 0,05) e na excreção de Na+ ( por centoDENa+ de 18,20 ± 2,17, P < 0,05). BTCI (1,0 µM) também aumenta por centoENa+ (de 22,8 ± 1,30 a 34,4 ± 3,48, P < 0,0590 minutos). Além disto, BTCI (3,0 µM) induziu um aumento da taxa de filtração glomerular (GFR; de 0,96 ± 0,02 para 1,28 ± 0,02 mL.g-1/min, P < 0,05, 60 minutos). O presente trabalho sugere fortemente que proteases semelhantes à quimiotripsina desempenham um papel no metabolismo renal de guanilinas e descreve, pela primeira vez, os efeitos renais induzidos por um membro da família de inibidores de proteases do tipo Bowman-Birk.

Dosis elevadas de aspirina disminuyen la natriuresis en hipertensos tratados con enalapril / High doses of aspirin reduce natriuresis in hypertensive patients treated with enalapril

Los inhibidores de la enzima convertidora de la angiotensina (IECA) han demostrado ser eficases en el tratamiento de la hipertensión arterial. Sin embargo, una importante proporción de hipertensos recibe además antiagregación plaquetaria con ácido acetil salicílico (AAS), y la consecuente inhibición de la síntesis de prostaglandinas con AAS atenuaría el efecto vasodilatador y la mayor excreción urinaria de sodio (Na(u)) atribuidas al IECA. Nuestro objetivo fue evaluar la interacción de dos dosis de AAS (81 y 325 mg/día) sobre el efecto hipotensor del enalapril y el impacto sobre la excreción de (Na(u)) en pacientes hipertensos. Se incluyeron 22 pacientes de ambos os sexos, entre 35 y 65 años. Todos reciberon enalapril, dieta hiposódica y, secuencialmente separadas por período de (wash out), las dos dois de AAS durante los setenta días del estudio. Se evaluó: presdión arterial sistólica (PAS), diastólica (PAD), media (PAM) y (Na(u)) en un período basal (PB), con 325 y 81 mg de AAS (P1 y P2 respectivamente). Comparando el PB con P1 y P2, se observó una reduccíon significativa de la PAS, PAD, PAM (p<0.01). Al comparar la PAS, PAD, PAM entre P1 y P2, no hubo diferencias significativas. La (Na(u)) en el PB fue mayor (p<0.01)con respecto al P1 y P2, y también P2 con respecto a P1. Estos resultados sugieren que en una población de pacientes hipertensos esenciales tratados con elapril y diferentes dosis de AAS, el tratamiento con dosis bajas de AAS está asociado a mejor control de la PA y mayor eliminación de sodio urinario.

Hypoglycemic, diuretic and hypocholesterolemic effect of winter cherry (Withania somnifera, Dunal) root.

Hypoglycemic, diuretic and hypocholesterolemic effects of roots of W. somnifera (ashvagandha) were assessed on human subjects. Six mild NIDDM subjects and six mild hypercholesterolemic subjects were treated with the powder of roots of W. somnifera for 30 days. Suitable parameters were studied in the blood and urine samples of the subjects along with dietary pattern before and at the end of treatment period. Decrease in blood glucose was comparable to that of an oral hypoglycemic drug. Significant increase in urine sodium, urine volume, significant decrease in serum cholesterol, triglycerides, LDL (low density lipoproteins) and VLDL (very low density lipoproteins) cholesterol were observed indicating that root of W. somnifera is a potential source of hypoglycemic, diuretic and hypocholesterolemic agents. Clinical observations revealed no adverse effects.

Renal effects of uroguanylin and guanylin in vivo

Uroguanylin and guanylin are newly discovered endogenous heat-stable peptides that bind to and activate a membrane bound guanylyl cyclase signaling receptor (termed guanylyl cyclase C; GC-C). These peptides are not only found in blood but are secreted into the lumen of the intestine and effect a net secretion of electrolytes (Na+, K+, Cl-, HCO3-) and fluid into the intestine via a cyclic guanosine-3',5'-monophosphate (cGMP) mechanism. GC-C is also the receptor for Escherichia coli heat-stable enterotoxin (STa) and activation by STa results in a diarrheal illness. Employing mouse renal in vivo models, we have demonstrated that uroguanylin, guanylin, and STa elicit natriuretic, kaliuretic, and diuretic effects. These biological responses are time- and dose-dependent. Maximum natriuretic and kaliuretic effects are observed within 30-40 min following infusion with pharmacological doses of the peptides in a sealed-urethra mouse model. Our mouse renal clearance model confirms these results and shows significant natriuresis following a constant infusion of uroguanylin for 30 min, while the glomerular filtration rate, plasma creatinine, urine osmolality, heart rate, and blood pressure remain constant. These data suggest the peptides act through tubular transport mechanisms. Consistent with a tubular mechanism, messenger RNA-differential display PCR of kidney RNA extracted from vehicle- and uroguanylin-treated mice show the message for the Na+/K+ ATPase g-subunit is down-regulated. Interestingly, GC-C knockout mice (Gucy2c -/-) also exhibit significant uroguanylin-induced natriuresis and kaliuresis in vivo, suggesting the presence of an alternate receptor signaling mechanism in the kidney. Thus, uroguanylin and guanylin seem to serve as intestinal and renal natriuretic peptide-hormones influencing salt and water transport in the kidney through GC-C dependent and independent pathways. Furthermore, our recent clinical probe study has revealed a 70-fold increase in levels of urinary uroguanylin in patients with congestive heart failure. In conclusion, our studies support the concept that uroguanylin and guanylin are endogenous effector peptides involved in regulating body salt and water homeostasis.

La glucosa en conjunto con péptidos derivados de cininógenos podrían actuar desde el aparato digestivo como bloqueadores de la acción diurética-natriurética del péptido natriurético auricular / Glucose in conjunction with peptides derived from kininogens might act from digestive tract as blockers of ANP mediated diuresis-natriuresis

This paper describes long term research efforts wich have lead: 1) to the identification of peptides present in pepsanurin, a peptidic fraction obtained by pepsin hydrolisis of plasma globulins that inhibits the renal excretory action of atrial natriuretic peptide (ANP) and 2) to the discovery of an unexpected role of glucose, as a requisite, for these inhibitory effects. The active peptides identified in pepsanurin are derived from plasma kininogens, substrates of the kallikrein-kinin system. Pro-kinins of 15, 16 and 18 aminoacids, and bradykinin itself, block ANP-induced diuresis and natriuresis when injected iv, ip or into, the duodenal lumen of anesthetized rats in picomol doses. Furthermore, a novel 20 aminoacids fragment derived from kininogen dominium-1, named PU-D1, is the most potent and longer lasting blocker of ANP renal effects. The anti-ANP effects of those peptides are prevented by B2- kinin receptor antagonists. The inhibition of ANP by kinins and PU-D1 was evident only in rats infused with isotonic glucose; whereas the excretory effect of ANP was not affected in fasted rats not infused, or infused with saline. These findings provide evidence that glucose facilitates liquid retention through a kinin-mediated inhibition of ANP excretory action that may be related to the prandial cycle

Losartan (DUP-753) blocks the natriuretic, kaliuretic and antidiuretic effect of intracerebroventricular injection of carbachol in water-loaded rats

We determined the effect of intracerebroventricular (icv) administration of losartan, an angiotensin II NG II), subtype I receptor (AT1) antagonist, on icv carbachol-induced natriuresis, kaliuresis and antidiuresis in water-loaded male Holtzman rats (250-300 g) with a cannula implanted into the lateral ventricle (LV). The rats were water loaded with 5 per cent of their body weight by gavage twice, with the second gavage one hour after the first. Carbachol (2 nmol in mul) was injected icv immediately after the second load. When losartan (DUP753, 50 nmol in 1 mul) was administered icv, it was given 3 min before carbachol. Previous icv treatment with losartan significantly reduced the icv carbachol-induced natriuresis (324 ñ 17 muEq/120 min), kaliuresis (103ñ15muEq /120min) and antidiuresis(13.5ñ2.1 ml/120 min) compared to the effects of previous icv injection of saline (Na+ excretion = 498 ñ 22 muEq/120 min; K+ excretion = 167 ñ 20 muEq/120 min; urine volume = 5.2 ñ 1.2 ml/l20 min). These results, reported as means ñ SEM for 12 rats in each group, are consistent with the hypothesis that AT1 subtype receptors participate in the regulation of body electrolyte balance.

The lysine-1 analog of guanylin induces intestinal secretion and natriuresis in the isolated perfused kidney

Guanylin is an endogenous peptide synthesized by several mammalian species that mimics the effects of a thermostable enterotoxin of Escherichia coli (STa: NTFYCCELCCNPACAGCY) in the gut. We have cloned a lysine-1 derivative of rat guanylin (Lys-1-NTCEICAYAACTGC) and tested its effects on ileal tissue membranes in Ussing chambers and in the isolated perfused rat kidney. Rabbit ileal mucosa membranes were mounted into a Ussing chamber and the effects of Lys-1 guanylin (Lys-1 G) and STa enterotoxin peptide on chloride secretion were determined by changes in short-circuit current (Isc). Lys-1 G (10 to 100 nM) showed a dose-dependent effect on chloride secretion with a maximal response estimated to be 52 microA/cm2. Lys-1 G mimics the effect of STa peptide, but the enterotoxin elicited a greater maximal effect of 120 microA/cm2 (p<0.01). Lys-1 G (2.5 microg/ml) promoted an increase in both urine flow (from 0.13 +/- 0.07 to 0.40 +/- 0.01 ml g(-1) min(-1), N = 4; P<0.05) and glomerular filtration rate (from 0.68 +/- 0.02 to 0.85 0.00 ml g(-1) min(-1), N = 4; P<0.01) in the isolated perfused kidney and a reduction of the fractional reabsorption of sodium (from 76.0 +/- 0.03 to 59.5 +/- 0.85 percent, N = 4; P<0.01). These maximal effects were accompanied by intense natriuretic effect observed 30 and 60 min after drug administration. The Lys-1 G analog similar to STa enterotoxin elicited intestinal chloride secretion and a natriuretic effect. These data demonstrate that the cloned peptide analog retains the biological activity of the native hormone and presents activity similar to STa. The properties of Lys-1 G resemble those of a factor formed during perfusion of the hypoxic rabbit kidney and named by us factor natriureticus similis (FNS).

Efectos del paration sobre la actividad de acetilcolinesterasa en rinón de rata

En el presente trabajo se estudió por métodos citoquímicos para microscopía óptica y electrónica, si el paratión (un inhibidos competitivo de acetilcolinesterasa que produce un efecto natriurético), es o no un inhibidor de la enzima a nivel renal, en dois no inhibitorias de AChE de glóbulos rojos (subtóxica). Se utilizaron ratas problema (RP) y ratas controles (RC) con deprivación de agua por 24 horas, inyectadas posteriormente con dosis de paratión intraperitoneal de 600 ug/100g de peso corporal. Para demonstración de actividad de AChE se realizaron incubaciones de riñón por el método de Karnovsky y Roots, variante Tsuji y Larabi. Los resultados de las cinco pruebas de incubación complementarias permiten concluir que existe actividad de AChE en corteza renal y que AChE a nivel renal es inhibida por dosis subtóxicas de paratión intraperitoneal. Se sugiere que el efecto natriurético del paratión se debería a este mecanismo de acción.

The role of angiotensin AT1 receptors in the diuretic, natriuretic, kaliuretic and blood pressure responses induced by angiotensin II activation of the median preoptic nucleus in conscious rats

We determined the effects of two classical angiotensin II (ANG II) antagonists, [Sar1, Ala8]-ANG II and [Sar1, Thr8]-ANG II, and losartan (a nonpeptide and selective antagonist for the AT1 angiotensin receptors) on diuresis, natriuresis, kaliuresis and arterial blood pressure induced by ANG II administration into the median preoptic nucleus (MnPO) of male Holtzman rats weighing 250-300 g. Urine was colected in rats submitted to a water load (5 percent body weight) by gastric gavage, followed by a second water load (5 percent body weight) 1 h later. The volume of the drug solutions injected was 0.5 µl over 10-15 s. Pre-treatment with [Sar1, Ala8]-ANG II (12 rats) and [Sar1, Thr8]-ANG II (9 rats), at the dose of 60 ng reduced (13.7 +/- 1.0 vs 11.0 +/- 1.0 +/- 1.2, respectively), whereas losartam (14 rats) at the dose of 160 ng totally blocked (13.7 +/- 1.0 vs.7.6 +/- 1.5) the urine excretion induced by injection of 12 ng of ANG II (14 rats)...

Renal vascular and excretory resistance to atrial natriuretic peptide in pre-cirrhotic, bile-duct ligated rats

Renal response to atrial natriuretic peptide in chronic cholestasis was studied in anaesthetized rats and in their isolated perfused kidneys. Cholestasis was induced by bile duct section after ligature, while controls were sham operated. Three weeks after surgery, cholestatic rats showed moderate arterial hypotension, elevated diuresis and no differences in urinary sodium, glomerular filtration rate (GFR) and fractional sodium excretion (FENa), when compared to controls. Isolated kidneys of cholestatic rats had equal basal diuresis and less natriuresis than the controls. Cholestatic rats presented blunted natriuretic and diuretic responses to iv injections of atrial natriuretic peptide (ANP 0.5 microgram), associated with reduced increments in GFR and FENa, when compared with controls. Similarly, the diuretic-natriuretic response of isolated kidneys to ANP (3.5 x 10(-9) M) was greatly attenuated in this group. ANP did not increase perfusion pressure in cholestatic rats, as it did in controls. These results indicate that animals with chronic cholestasis present refractoriness to ANP, which might be mediated by a direct impairment at the renal vascular and tubular sites for ANP action

Role of angiotensin II in the antinatriuresis that follows acute volume depletion

El objetivo del presente experimento fue conocer el papel de la angiotensina II en la retención renal de sodio que sigue a la disminución aguda de volúmen. El modelo utilizado fue una disminución aguda de volúmen, por sangrado, seguida de expansión salina. Se estudiaron cuatro grupos de seis perros cada uno: I = expansión salina: expansión salina equivalente al 8 porciento del peso corporal, en período de una hora; II = disminución aguda de volúmen: sangrado equivalente al 2 porciento del peso corporal, en 5 minutos, seguido una hora después por expansión salina similar al grupo I; III = expansión salina + captopril; y IV = disminución aguda de volumen + captopril o sea, similar a los grupos I y II en perros tratados con altas dosis del inhibidor de la enzima convertidora de angiotensina captopril (400 mg vía oral la noche anterior; 1 mg/kg en bolo iv al término de la cirugía, seguido por infusión continua de 20 *g/kg/min). Los animales fueron anestesiados con pentobarbital y las mediciones fueron realizadas 30 minutos antes del sangrado y durante los 60 minutos de expansión salina. La función hemodinámica renal se mantuvo similar a los cuatro grupos. No hubo diferencia significativa en la filtración glumerular (inulina), en el flujo sanguíneo renal (para-aminohipurato) ni en presión arterial durante todo el experimento. En cambio, el incremento en la excreción urinaria de sodio, durante la expansión salina, fue mayor en los grupos sometidos únicamente a expansión salina, que en aquellos que fueron expuestos a sangrado. El aumento en la fracción excretada de sodio, del período control al final de la expansión salina, fue de 0.6 ñ 0.2 a 6.4 ñ 1 porciento en el grupo I y de 1.1 ñ 0.3 a 8.5 ñ 1.3 porciento en el grupo III. En cambio en los grupos sometidos a sangrado, la fracción excretada de sodio únicamente aumentó de 0.8 ñ 0.2 a 3.5 ñ 0.7 porciento en el grupo II y de 1.3 ñ 0.4 a 4.1 ñ 0.6 porciento en el grupo IV. Por lo tanto, el incremento en la excreción urinaria de sodio fue significativamente menor en los animales sometidos a disminución aguda de volumen, independientemente del tratamiento con captopril. La disminución en la natriuresis no puede explicarse por diferencias en la hemodinámica renal. Este resultado sugiere que el sistema renina angiotensina no es el principal mediador de la retención de sodio que sigue a la deshidratación aguda.

Is the renal (Na + K)-ATPase modulated by intracellular messengers?

Se discuten los mecanismos celulares básicos involucrados en la regulación de la actividad de la (Na + K) -ATPasa. Numerosos ligandos pueden participar en la modulación rápida de esta actividad enzimática (mensajeros intracelulares). El Ca**2+ citosólico juega un papel clave em mediar los cambios inducidos por hormonas o agonistas de receptores. A su vez, proteínas intracelulares dependientes de Ca**2+, como calmodulina, calnaktina u otras, son necesarias para estos cambios. La fosforilación de proteínas efectoras que resulta de la activación de PKC, PKA, o CaM-quinasa II, puede provocar cambios en la actividad de la (Na + K)-ATPasa, ya sea por un efecto directo sobre la subunidad catalítica o por, modulación del intercambiador Na+/H+ que afecta el Na+ intracelular, cuya concentración es crítica para la actividad de esta enzima. A pesar de la ubicuidad de la (Na + K)-ATPasa en diversos órganos y tejidos, la respuesta a los moduladores depende parcialmente de la heterogeneidad de la subunidad a que da lugar a la existencia de diferentes isoformas. La relativa abundancia de a1, a2, a3 u otras isoformas, es específica para el tejido y representa otra manera de regulación entre los diferentes tipos celulares. Mientras estos mecanismos ocurren en diversos tipos de células, el riñón muestra una respuesta antagónica respecto de otros tejidos tales como hígado o cerebro. La relevancia funcional de los mecanismos de adaptación aguda de la (Na + K) -ATPasa que han sido discutidos en esta revisión, está alcanzando reconocimiento en el caso de la enzima renal, lo que puede contribuir a estimular la aplicación de nuevos enfoques al estudio de la regulación rápida de la bomba en términos moleculares