Diferencias de género en presión arterial, función renal y respuesta a la dieta hipersódica en ratas Wistar / Gender differences in blood pressure, renal function and response to a high-sodium diet in Wistar rats

Introducción: Es conocido que el sexo es un condicionante de la regulación renal de sodio y de la presión arterial. Material y métodos: Se estudiaron ratas Wistar machos y hembras a los 150 días de vida, con dieta normo o hipersódica (NaCl 1% v.o.) en los últimos cinco. Se determinaron presión arterial media (PAM), natriuresis, filtrado glomerular (VFG), flujo plasmático renal (FPR) y aldosterona plasmática. Se estudió la expresión Na+,K+-ATPasa total (t-NKA) y defosforilada (d-NKA), citocromo P4504A (CYP4A), cotransportadores Na+,K+,2Cl- tipo 2 (NKCC2) y Na+/Cl- (NCC) y por PCR el ARNm de la cadena α1 de NKA (Atp1a1) en corteza y médula renal. Resultados: La PAM fue mayor y la natriuresis menor en los machos bajo ambas dietas. Con ingesta hipersódica la aldosterona bajó en ambos sexos, el VFG fue menor en hembras y el FPR aumentó en machos (4,09 ± 0,17 vs 2,81 ± 0,12 ml/min/gR; p<0,01 vs dieta normosódica). La t-NKA, d-NKA y Atp1a1 en médula fue mayor en machos con ambas dietas. Con ingesta hipersódica, t-NKA en médula y d-NKA en corteza y médula disminuyeron en hembras y solamente d-NKA disminuyó en médula de machos. Asimismo, aumentó CYP4A y disminuyó NKCC2 y NCC en hembras, mientras que aumentó NKCC2, sin cambios en NCC, en machos. Conclusión: El sexo condiciona la presión arterial y el balance de sodio, disminuyendo su reabsorción en hembras y aumentando el FPR en machos. Esto sugiere posibilidades de estudio diferenciales según sexo en trastornos del metabolismo del sodio

Introduction: It is known that sex is a determinant of renal sodium regulation and blood pressure. Methods: Male and female Wistar rats, which were 150 days old and a diet with normal or high levels of sodium (NaCl 1% v.o.), were studied for the last five days. Mean blood pressure (MBP), natriuresis, glomerular filtration rate (GFR), renal plasma flow (RPF) and plasma aldosterone level were established. The following were studied: expressions of total Na+,K+,-ATPase (t-NKA); dephosphorylated NKA (d-NKA); cytochrome P4504A (CYP4A); Na+K+-2Cl- (NKCC2) and Na+/Cl- (NCC) cotransporters. The mRNA expression of the NKA α1 (Atp1a1) chain was examined through PCR analysis in the renal cortex and marrow. Results: Male rats having both types of diet showed higher MBP and lower natriuresis. High sodium intake triggered lower aldosterone levels in both sexes; GFR was lower in females and RPF was higher in males (4.09 ± 0.17 vs. 2.81 ± 0.12 ml/min/gr; p<0.01 vs. diet with a normal sodium level). Marrow t-NKA, d-NKA and Atp1a1 were higher in males on both diets. High sodium intake caused lower marrow t-NKA as well as lower cortex and marrow d-NKA in females. In the case of males, only marrow d-NKA decreased. Furthermore, females showed a higher level of CYP4A and lower levels of NKCC2 and NCC, whereas males showed higher levels of NKCC2 and no variations in NCC. Conclusion: Sex conditions blood pressure and sodium balance, reducing resorption in females and increasing RPF in males. This suggests the possibility of studying sodium metabolism disorders differently according to sex

Paradoxo do cálcio - o que temos a temer? / The calcium paradox - What should we have to fear?

O paradoxo do cálcio foi pela primeira vez citado em 1966 por Zimmerman et al. A partir daí, ganhou grande interesse por parte da comunidade científica internacional devido ao fato da ausência do íon cálcio produzir na célula muscular cardíaca dano semelhante à lesão de isquemia-reperfusão. Apesar de não serem conhecidos todos os mecanismos envolvidos no processo da lesão celular no paradoxo do cálcio, a conexão intercelular mantida somente pelo nexus parece ter papel chave na fragmentação celular. A adição de pequenas concentrações de cálcio, bloqueadores de canal de cálcio, hiponatremia ou hipotermia são importantes para evitar que haja lesão celular no momento da reperfusão com soluções com concentração fisiológica de cálcio.

The calcium paradox was first mentioned in 1966 by Zimmerman et al. Thereafter gained great interest from the scientific community due to the fact of the absence of calcium ions in heart muscle cells produce damage similar to ischemia-reperfusion. Although not all known mechanisms involved in cellular injury in the calcium paradox intercellular connection maintained only by nexus seems to have a key role in cellular fragmentation. The addition of small concentrations of calcium, calcium channel blockers, and hyponatraemia hypothermia are important to prevent any cellular damage during reperfusion solutions with physiological concentration of calcium.

Hypertension: Salt restriction, sodium homeostasis, and other ions.

Salt is composed of Sodium Chloride (NaCl) which in body water becomes essential electrolytes, viz., Sodium (Na + ) and Chloride (Cl - ) ions, including in the blood and other extracellular fluids (ECF). Na + ions are necessary cations in muscle contractions and their depletion will effect all the muscles in body including smooth muscle contraction of blood vessels, a fact which is utilized in lowering the blood pressure. Na+ ions also hold water with them in the ECF. Na + homeostasis in body is maintained by thirst (water intake), kidneys (urinary excretion) and skin (sweating). In Na + withdrawal, body tries to maintain homeostasis as far as possible. However, in certain conditions (e.g., during exercise, intake of drugs and in disorders causing Syndrome of Inappropriate Anti Diuretic Hormone Secretion (SIADH), diuretics, diarrhea) coupled with moderate or severe dietary salt restriction (anorexia nervosa), hyponatremia can get precipitated. Hyponatremia is one end point in the spectrum of disorders caused by severe Na + depletion whereas in moderate depletion it can cause hypohydration (or less total body water) and lower urinary volume (U v ). Moreover, salt sensitivity varies in various populations leading to different responses in relation to dietary Na + intake. Diabetes and Hypertension often co-exist but Na + withdrawal in salt sensitive subjects worsens diabetes though hypertension gets better and reverse occurs in salt loading. Therefore, Na + or salt restriction may be non-physiological. In hypertensive subjects other alternatives to Na + withdrawal could be Potassium (K + ) and Calcium (Ca 2+ ) supplementation. Further studies are required to monitor safety/side effects of salt restriction.

Actividad del sistema dopaminérgico renal en ratas con distinto contenido de sodio en la dieta / Activity of the renal dopaminergic system in rats

La dopamina (DA) renal modula la excreción de sodio y agua y la presión arterial por medio de receptores D1 (D1R) y D2 y es degradada por las enzimas monoamino-oxidasa (MAO) y catecol-O-metiltransferasa (COMT). Nuestro propósito es estudiar el patrón de excreción urinaria de DA (UDAV) y la actividad de MAO y COMT durante el consumo de dietas con distinto contenido de sodio.

Na+-Ca2+ exchanger modulates Ca2+ content in intracellular Ca2+ stores in rat osteoblasts

Na+ -Ca2+ exchanger (NCX) transports Ca2+ coupled with Na+ across the plasma membrane in a bi-directional mode. Ca2+ flux via NCX mediates osteogenic processes, such as formation of extracellular matrix proteins and bone nodules. However, it is not clearly understood how the NCX regulates cellular Ca2+ movements in osteogenic processes. In this study, the role of NCX in modulating Ca2+ content of intracellular stores ([Ca2+](ER)) was investigated by measuring intracellular Ca2+ activity in isolated rat osteoblasts. Removal of extracellular Na+ elicited a transient increase of intracellular Ca2+ concentration ([Ca2+](i)). Pretreatment of antisense oligodeoxynucleotide (AS) against NCX depressed this transient Ca2+ rise and raised the basal level of [Ca2+](i). In AS-pretreated cells, the expression and activity of alkaline phosphatase (ALP), an osteogenic marker, were decreased. However, the cell viability was not affected by AS-pretreatment. Suppression of NCX activity by the AS-pretreatment decreased ATP-activated Ca2+ release from intracellular stores and significantly enhanced Ca2+ influx via store operated calcium influx (SOCI), compared to those of S-pretreated or control cells. These results strongly suggest that NCX has a regulatory role in cellular Ca2+ pathways in osteoblasts by modulating intracellular Ca2+ content.

Discrimination of transport systems of L-tyrosine in mouse mammary gland: characterization of system T.

On the basis of inhibition analysis, tyrosine uptake in mouse mammary gland was found to be mediated by Na(+)-dependent and Na(+)-independent systems. Na(+)-dependent system was insensitive to 2-(methylamino) isobutyric acid (MeAIB), with an apparent Km of 1.67 mM and maximal velocity 74.5 nmol.g-1 cell. min-1. Competition experiments showed the presence of two distinct Na(+)-independent components of tyrosine uptake. One component was sensitive to 2-aminobicyclo (2,2,1) heptane-2-carboxylic acid (BCH) and was similar to the system L, with an apparent Km of 0.23 mM and maximum velocity of 31 nmol.g-1 cell.min-1. Second component was BCH-insensitive but tryptophan-sensitive, with an apparent Km of 15.75 mM and Vmax of 157.5 nmol.g-1cell.min-1. BCH-insensitive, tryptophan-sensitive system was a low affinity system. It approached steady state slowly and was more sensitive, relative to the system L, to n-ethylmaleimide inhibition. Tyrosine uptake through this system did not respond to trans-stimulation, whereas system L mediated uptake responded considerably. BCH-insensitive, tryptophan-sensitive component of Na(+)-independent tyrosine uptake is attributed to the system T, previously described only in human red blood cells and rat liver cells.

Secretory effect of serotonin on jejunal response to cholera toxin, in dog

A substância mediadora liberada pela toxina da cólera e que estimula a secreçäo intestinal é ainda desconhecida. Sabe-se que a serotonina está envolvida no estímulo secretor intestinal de água e eletrólitos. Tendo em vista a avaliaçäo de um provável papel da serotonina na induçäo secretora jejunal pela toxina da cólera, calcularam-se os volumes de água, sódio, potássio e cloreto, bem como os níveis imunorreativos de serotonina, em alça de Thiry-Vella canina. A administraçäo de toxina provocou um aumento na secreçäo de todos os eletrólitos e do fluxo de serotonina. Esses resultados sugerem que a toxina da cólera induz à liberaçäo de serotonina na luz intestinal, talvez como um mediador da secreçäo hidroeletrolítica entérica

Efeitos antagônicos de plantas medicinais na diurese do rato / Antagonistic effects of medicine plants in the rat diuresis

Os autores estudaram os efeitos da sobrecarga aquosa de folhas secas de jamboläo e de casca seca de barbatimäo, por via gástrica, na excreçäo renal de água, de sódio e de potássio do rato. Em relaçäo ao volume urinário observou-se uma diurese com o emprego do jamboläo e uma antidiurese com o emprego do barbatimäo, entretanto näo se observou alteraçäo na excreçäo de sódio e de potássio, após o emprego dos extratos das duas plantas