A Compound Isolated from Phyllanthus tenellus Demonstrates Metabolic and Vascular Effects In Vitro.

Common chronic conditions such as metabolic syndrome and diabetes are increasingly associated to metabolic and cardiovascular complications. Although Phyllanthus tenellus leaves have been used in decoctions as a popular remedy to control blood glucose levels and hypertension, its use needs a scientific basis. This study was therefore undertaken to report a phytochemical analysis of P. tenellus leaves and to test if the main active compound has potential to simultaneously tackle several pathophysiological features of metabolic syndrome and diabetes-related metabolic and vascular disorders such as hyperglycaemia, increased platelet activation, and endothelial dysfunction. We performed a partition of the methanolic extract of P. tenellus leaves among different organic solvents followed by chromatographic separation guided by the rat liver microsomal glucose-6-phosphatase assay. Two known tannins were identified by spectroscopic methods as pinocembrin-7-O-[3″-O-galloyl-4″,6″-(S)-hexahydroxydiphenoyl]-α-D-glucose, named P7OG by us, and gemin D. The structural determination of the isolated compounds was based on spectral data. The ability of the main active component, P7OG, to inhibit human platelet aggregation and to modify vascular reactivity of rat aortic rings incubated with high glucose (D-glucose 55 mM) was then evaluated. P7OG was further able to inhibit platelet aggregation induced by adenosine 5'-diphosphate and collagen, showed vasorelaxant effects in arteries precontracted with phenylephrine, and reverted the endothelium-dependent impairment effect of high glucose in rat aortic rings. In conclusion, one tannin isolated from P. tenellus showed promising metabolic, antiaggregant, and vascular effects, which suggests the potential beneficial use of P. tenellus to tackle complex cardiometabolic diseases.

Triterpene saponins from Billia rosea.

Five previously undescribed triterpene saponins, billiosides A-E, and a known analogue, were isolated from the seeds of Billia rosea (Planch. & Linden) C. Ulloa & P. Jørg. Their structures were elucidated on the basis of extensive 1D and 2D NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC) and mass spectrometry as (3ß,21ß,22α)-3-[(2-O-ß-D-glucopyranosyl-O-[α-L-arabinopyranosyl-(1 â†’ 4)]-ß-D-glucopyranosyl)oxy]-21-[((2E,6S)-2,6-dimethyl-6-hydroxyocta-2,7-dienoyl)oxy]-22-(acetyloxy)-24-hydroxyolean-12-en-28-oic acid, (3ß,21ß,22α)-3-[(2-O-ß-D-galactopyranosyl-ß-D-glucopyranosyl)oxy]-21,22-dihydroxyolean-12-en-28-yl O-α-L-arabinopyranosyl-(1 â†’ 4)-ß-D-glucopyranoside, (3ß,21ß,22α)-3-[(2-O-ß-D-galactopyranosyl-O-[α-L-arabinopyranosyl-(1 â†’ 4)]-ß-D-xylopyranosyl)oxy]-21,22-dihydroxyolean-12-en-28-yl O-ß-D-glucopyranoside, (3ß,21ß,22α)-3-[(2-O-ß-D-galactopyranosyl-O-[α-L-arabinopyranosyl-(1 â†’ 4)]-ß-D-glucopyranosyl)oxy]-21,22-dihydroxyolean-12-en-28-yl O-ß-D-glucopyranoside, (3ß,21ß,22α)-3-[(2-O-ß-D-galactopyranosyl-O-[α-L-arabinopyranosyl-(1 â†’ 4)]-ß-D-glucopyranosyl)oxy]-21,22-dihydroxyolean-12-en-28-yl O-ß-D-glucopyranosyl-(1 â†’ 6)-ß-D-glucopyranoside, and dipteroside A. Billiosides B and C exhibited moderate effects when tested as hepatic glucose-6-phosphatase inhibitors and as glucose intestinal absorption inhibitors, using in situ rat intestinal segments.

(6R,9S)-6"-(4"-hydroxybenzoyl)-roseoside, a new megastigmane derivative from Ouratea polyantha and its effect on hepatic glucose-6-phosphatase.

A new megastigmane derivative, (6R,9S)-6'-(4"-hydroxybenzoyl)-roseoside (1) and two known compounds, the biflavoneagathisflavone (2) and 4-hydroxybenzoic acid (3) were isolated and purified from leaves and stems of Ouratea polyantha Engl. Agathisflavone was isolated in a single high-speed countercurrent chromatography run, while the megastigmane was purified in two steps, by using a combination of high-speed countercurrent chromatography and analytical column chromatography. All structures were elucidated on the basis of spectral evidence and comparison with literature data. Compound 1 was characterized by [alpha]D20, UV-Vis, IR, MS, 1H NMR, 13C NMR, HMQC, HMBC, COSY and NOESY. Compounds 1 and 2 showed an inhibitory effect of 63.6 and 13.7% on the G-6-Pase intact microsomes, respectively.

Couepia paraensis: estudio fitoquímico, ensayos de citotoxicidad y de inhibición de la glucosa-6-fosfatasa / Couepia paraensis: phytochemical study, cytotoxicity assays and inhibition of glucose-6-phosphatase

From the cholroform extract of the aerial parts of Couepia paraensis the triterpenes beta-sitosterol1, betulinic acid acetate 2, and oleanolic acid acetate 3, were isolated. Six triterpenes from the chloroform-methanol, acids: oleanolic 4, pomolic 5, ursolic 6, betulinic 7, 6-beta-hydroxybetulínic 8. Additionally from the methanolic extract three flavonoids were isolated: mricetin 9, quercetin 10 y rutina 11. The chloroform and chloroform-methanol extracts were not citotoxic at concentration of 2,5 and 3,1 ug/ml respectively after 24 hours of incubation. The methanol extract was found to be harmless to a concentration of 50 ug/ml, both at 24 hours (LD50 = 10.77 ug/ml) and 120 hours (LD50 = 28.86 ug/ml) of incubation. Only the methanol extract showed significant inhibition (41 percent) of the activity of G-6-Pase in intact microsomes without affecting the activity of the enzyme in microsomes broken.

Se aislaron e identificaron tres triterpenos: beta-sitosterol 1, acetato del ácido betulínico, 2 y acetato del ácido oleanólico 3 del extracto clorofórmico. Seis triterpenos del extracto cloroformo: metanol (9:1) que fueron identificados como ácidos: oleanólico 4, pomólico 5, ursólico 6, betulínico 7, 6-beta-hidroxibetulínico 8. Mientras que del extracto metanólico se identificaron 3 flavoniodes: miricetina 9, quercetina 10 y rutina 11. Los extractos de cloroformo y cloroformo /metanol resultaron inocuos hasta las concentraciones de 2,5 y 3,1ug/ml respectivamente, después de 24 horas de incubación. El extracto metanólico es inocuo hasta una concentración de 50 ug/ml, tanto a 24 horas (LD50 = 10,77 ug/ml) como a 120 horas (LD50 = 28,86 ug/ml) de incubación. Solamente el extracto metanólico mostró una inhibición significativa (41 por ciento) de la actividad de la G-6-Pasa de microsomas intactos sin afectar la actividad de la enzima en microsomas rotos.

Phenolic derivatives from Ruprechtia polystachya and their inhibitory activities on the glucose-6-phosphatase system.

Two new compounds, 5-methyl-2-(2-methylbutanoyl)phloroglucinol 1-O-(6-O-ß-D-apiofuranosyl)-ß-D-glucopyranoside (1) and trans-2,3-dihydrokaempferol 3-O-(4-O-sulfo)-α-L-arabinopyranoside (2), together with 14 known flavonoids, trans-dihydrokaempferol 3-O-α-L-arabinopyranoside (3), trans-taxifolin 3-O-α-L-arabinofuranoside (4), quercetin 3-O-α-L-rhamnopyranoside (5), quercetin 3'-O-α-L-arabinofuranoside (6), catechin 3-O-α-L-rhamnopyranoside (7), trans-taxifolin 3-O-α-L-arabinopyranoside (8), cis-dihydrokaempferol 3-O-α-L-arabinopyranoside (9), catechin (10), myricetin 3-O-α-L-rhamnopyranoside (11), quercetin 3-O-α-L-arabinopyranoside (12), quercetin 3-O-α-L-arabinofuranoside (13), quercetin 3-O-(3″-galloyl)-α-L-rhamnopyranoside (14), quercetin 3-O-(2″-galloyl)-α-L-rhamnopyranoside (15), and epicatechin 3-O-gallate (16), were isolated from the leaves of Ruprechtia polystachya Griseb. (Polygonaceae). Their structures were established on the basis of extensive 1D- and 2D-NMR experiments as well as MS analyses. All compounds, except 1, showed inhibition of the enzyme glucose-6-phosphatase in intact microsomes.

Inhibition of glucose intestinal absorption by kaempferol 3-O-α-rhamnoside purified from Bauhinia megalandra leaves.

Glucose intestinal absorption (GIA) is one of the factors that increase glycemia. Its reduction could be an important factor in decreasing hyperglycemia in diabetic patients. It has been shown that the aqueous extract of Bauhinia megalandra leaves inhibits GIA. In the present study we identified a compound present in the extract of B. megalandra responsible for the biological effect. The methanol extract of B. megalandra leaves was fractionated using different solvents, and high-speed counter-current chromatography yielding two pure compounds identified by (1)H NMR and (13)C NMR as kaempferol 3-O-α-rhamnoside and quercetin 3-O-α-rhamnoside. The first one increased the K(M) without changes in the V(MAX) of GIA. In addition it exerted an additive inhibitory effect, on GIA, when combined with phlorizin. We suggest that kaempferol 3-O-α-rhamnoside is a competitive inhibitor of intestinal SGLT1 cotransporter.

Purificación parcial de un compuesto presente en las hojas de bauhinia megalandra capaz de inhibir la absorción intestinal de glucosa / Partial purification of a compound present in the leaves of Bauhinia megalandra capable of inhibiting intestinal glucose absorption

En la actualidad muchas investigaciones se han volcado al estudio de la actividad biológica de varias plantas que se considera, en el saber de los pueblos, puedan aliviar los síntomas en pacientes con diabetes, tal es el caso de Bauhinia megalandra. El estudio fitoquímico de las hojas de dicha planta se realizó guiado por bioensayos, evaluando el efecto de cada fracción obtenida sobre la absorción intestinal de glucosa con la finalidad de encontrar aquella que presente el mayor efecto inhibitorio sobre dicha actividad biológica, utilizando para su medición segmentos de intestino de rata aislados in situ. Luego de una serie de extracciones secuenciales con diferentes solventes orgánicos y fraccionamiento por cromatografía de columna en silica gel 60, se logró aislar y caracterizar por métodos espectroscópicos una fracción altamente enriquecida con el flavonoide apigenina glucosilada en el carbono ocho. Dicha fracción fue capaz de inhibir la absorción intestinal de glucosa en un 47,34% con respecto al control, y de generar un efecto aditivo cuando se ensayo junto a la floricina

At present, it has been an increase in the research of the biological activity of plants used by the traditional medicine for the empirical treatment of the diabetes mellitus, such as Bauhinia megalandra. The phytochemical study of the leaves of these plants was done guided by bioassay, evaluating the effect of each fraction on the glucose intestinal absorption, using in situ rat intestinal segments. After a sequential series of extractions with organic solvents and fractionation by column chromatographic on silica gel 60, we isolated a fraction characterized by spectroscopic method to be highly enriched in the flavonoid apigenin glicolisated in the carbon eight. This fraction was able to inhibit in a 47,34% the intestinal glucose absorption compared to control, and showed an additive effect when used simultaneously with phloricin

Effect of flavonoids from Exellodendron coriaceum (Chrysobalanaceae) on glucose-6-phosphatase.

From the n-butanol extract of the aerial parts of Exellodendron coriaceum (Benth.) Prance the flavonoids quercetin-3-O-beta-D-galactopyranoside (1), quercetin-3-O-alpha-L-arabinopyranoside (2), quercetin-3-O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-rhamnopyranoside (3), and quercetin-3-O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-galactopyranoside (4) were isolated. Additionally from this extract three flavonoids were isolated and partially characterized as quercetin glycosides. All these compounds were tested for their hypoglycemic activity using the glucose-6-phosphatase microsomal hepatic system. The flavonoids inhibited the activity of the enzyme when intact microsomes were used, the highest percentage of inhibition being 65%. To the best of our knowledge, this is the first report of chemical and biological activity of E. coriaceum.

Antidiabetic and antiradical activities of plants from Venezuelan Amazon / Atividades antidiabética e anti-radicalar de plantas da Amazônia venezuelana

Os extratos aquoso e etanólico derivados de doze espécies coletadas na Amazônia venezuelana foram testados quanto à atividade antioxidante utilizando um radical DPPH e o efeito inibitório sobre a hidrólise de glicose-6-fosfato nos microssomas intactos e perturbados. Sem exceção, todos os extratos inibiram, em maior ou menor grau, a atividade enzimática microssomal de G-6-Pase, resultando em maior inibição nos microssomas intactos do que nos perturbados. Efeitos marcantes foram observados para os extratos aquoso e etanólico de: Tontelea ovalifolia, Gustavia pulchra, Phthirusa verruculosa, Phthirusa castillana, Psittacanthus acimarius, Tetrapterys styloptyera e Vismia japurensis. Os extratos etanólicos foram seqüestradores do radical DPPH mais eficazes do que os correspondentes extratos aquosos em todos os casos. O extrato etanólico de Endlicheria anomala e o extrato aquoso de Phthirusa verruculosa exibiram as melhores CI50 com 100 e 250.0 ppm, respectivamente. Os valores de Kobs calculados para os extratos alcoólicos foram mais baixos do que os dos extratos aquosos das mesmas espécies, exceto Psittacanthus acimarius. Estes resultados poderiam estar relacionados a diferentes concentrações, ou mais provavelmente a diferentes composições de princípios ativos em ambos extratos.

The aqueous and ethanol extracts derived from twelve plant species collected in the Venezuelan Amazon have been tested for antioxidant activity using a DPPH radical and inhibitory effect on the hydrolysis of glucose-6-phosphate in intact and disrupted microsomes. Without exception, all the extracts inhibited, to a greater or lesser degree, microsomal G-6-Pase enzymatic activity, resulting in greater inhibition on intact microsomes than on disrupted ones. Marked effects were observed for aqueous and ethanol extracts of: Tontelea ovalifolia, Gustavia pulchra, Phthirusa verruculosa, Phthirusa castillana, Psittacanthus acimarius, Tetrapterys styloptyera and Vismia japurensis. Ethanol extracts were more effective DPPH radical scavengers than the corresponding aqueous extracts in all the cases. The ethanol extract of Endlicheria anomala and the aqueous extract of Phthirusa verruculosa, showed the best IC50 with 100 and 250.0 ppm, respectively. The Kobs calculated for the alcoholic extracts were lower than those of the aqueous extracts for the same species, except Psittacanthus acimarius. These results could be related to different concentrations, or more likely different compositions of active principles in both extracts.

[Glucose-6-phosphatase from nuclear envelope in rat liver]. / Glucosa-6-fosfatasa de envoltura nuclear de hígado de rata.

Nuclear envelope (NE) and microsomal glucosa-6-phosphatase (G-6-Pase) activities were compared. Intact microsomes were unable to hydrolyze mannose-6-phosphate (M-6-P), on the other hand, intact NE hydrolyzes this substrate. Galactose-6-phosphate showed to be a good substrate for both NE and microsomal enzymes, with similar latency to that obtained with M-6-P using microsomes. In consequence, this substrate was used to measure the NE integrity. The kinetic parameters (Kii and Kis) of the intact NE G-6-Pase for the phlorizin inhibition using glucose-6-phosphate (G-6-P) and M-6-P as substrates, were very similar. The NE T1 transporter was more sensitive to amiloride than the microsomal T1. The microsomal system was more sensitive to N-ethylmalemide (NEM) than the NE and the latter was insensitive to anion transport inhibitors DIDS and SITS, which strongly affect the microsomal enzyme. The above results allowed to postulate the presence of a hexose-6-phosphate transporter in the NE which is able to carry G-6-P and M-6-P, and perhaps other hexose-6-phosphate which could be different from that present in microsomes or, if it is the same, its activity could by modified by the membrane system where it is included. The higher PPi hydrolysis activity of the intact NE G-6-Pase in comparison to the intact microsomal, suggests differences between the Pi/PPi transport (T2) of both systems. The lower sensitivity of the NE G-6-Pase to NEM suggests that the catalytic subunit of this system has some differences with the microsomal isoform.

Glucosa-6-fosfatasa de envoltura nuclear de hígado de rata / Glucose-6-phosphatase from nuclear envelope in rat liver

Se comparó la actividad de la glucosa-6-fosfatasa (G-6-Pasa) de envoltura nuclear (EN) con la microsomal. Los microsomas intactos fueron incapaces de hidrolizar manosa-6-fosfato (M-6-P); por el contrario, la EN intacta fue capaz de hidrolizar dicho substrato. La galactosa-6-fosfato mostró ser un buen substrato tanto para la enzima de EN como microsomal, con una latencia similar a la obtenida para M-6-P utilizando microsomas, por lo cual galactosa-6-fosfato fue usado para medir el porcentaje de EN intactas. Los parámetros cinéticos (Kii y Kis) de la inhibición por floricina de la G-6-Pasa de EN intactas, utilizando glucosa-6-fosfato (G-6-P) y M-6-P como substrato, fueron aproximadamente iguales. El transportador T1 de EN fue más sensible a la amiloride que el microsomal. Por el contrario, el sistema microsomal fue más sensible al efecto de N-etilmaleimida (NEM) que el de EN y este último, fue prácticamente insensible a los inhibidores de transporte aniónico DIDS y SITS, los cuales afectan fuertemente la enzima microsomal. Los resultados anteriores permiten sugerir que en la EN existe un transportador de hexosas-6-fosfato, capaz de transportar G-6-P y M-6-P y quizás otras hexosas-6-fosfato y que, o es diferente al T1 microsomal, o si es igual es influenciado por las características del sistema membranoso en el cual está incluido. La capacidad superior de hidrólisis de PPi de la G-6-Pasa de EN intacta, en comparación con la de microsomas intactos, sugiere diferencias en el transportador de Pi/PPi (T2) de ambos sistemas. La menor sensibilidad de la G-6-Pasa de EN al NEM sugiere que la subunidad catalítica de este sistema también podría tener algunas diferencias con la isoforma microsomal.

Efecto del extracto acuoso de hojas de Bauhinia megalandra sobre la glucogenólisis hepática en ratas / Effect of aqueous extract of leaves of Bauhinia megalandra glucogenólisis on the liver in rats

El extracto acuoso de las hojas de Bauhinia megalandra ha sido muy empleado en Venezuela en el tratamiento empírico de la diabetes mellitus. En el presente trabajo se estudió el efecto del extracto acuoso de B. megalandra sobre la glucogenolísis hepática estimulada por adrenalina o dibutiril AMPc. La administración oral del extracto de la planta, a ratas alimentadas, disminuyó de una manera estadísticamente significativa el incremento de la glicemia promovido por la adrenalina. De igual manera, rebanadas de hígado de ratas alimentadas incubadas en presencia del extracto de B. megalandra produjeron menos glucosa en respuesta a la adrenalina o al dibutiril AMPc que los controles. Estos resultados indican una disminución de la glucogenolísis hepática por efecto del extracto acuoso de hojas de B. megalandra, probablemente por inhibición de la enzima glucosa-6-fosfatasa.

Renal glycosuria induced by acute thioacetamide administration to rats

La administración de tioacetamida (TAA) en ratas (75 mg/kg de peso vía subcutánea) produjo un incremento estadísticamente significativo de la eliminación urinaria de glucosa, Na+ y fosfato. Adicionalmente, ocurrió una disminución de la presión arterial y de la velocidad de filtración glomerular, sin cambios en la excreción urinaria de K+, H+, aminoácidos ni en la glucemia. Se observó una disminución del 60 por ciento y 75 por ciento del Tmax y Tmin para la glucosa, respectivamente. La TAA alteró la captación de [14C]-glucosa por vesículas de membrana de borde apical renal (BBMV), disminuyendo en un 16 por ciento el pico de captación a los 30 s, en un 63 por ciento la Vmax y en aproximadamente un 82 por ciento el Km. También disminuyó en un 52 por ciento el Kd y cerca de un 59 por ciento el número de sitios de unión para [3H]-floricina en BBMV. Estos resultados sugieren fuertemente que la droga reduce la cantidad del co-transportador Na+/glucosa (SGLT1) presente en la membrana apical del túbulo contorneado proximal. La disminución de la temperatura de transición de la maltasa y de la fosfatasa alcalina de las BBMV así como el incremento de la cantidad de ácidos grasos insaturados presentes en los fosfolipidos de las BBMV sugieren un incrementoen la fluidez de dichas membranas. Estos resultados pudieran explicar el incremento en la afinidad del SGLT1 por la glucosa producida por la TAA.

Evaluation of flavonoids from Bauhinia megalandra leaves as inhibitors of glucose-6-phosphatase system.

From the methanol extract of Bauhinia megalandra fresh leaves, eight flavonoids were isolated and evaluated by rat liver microsomal glucose-6-phosphatase (G-6-Pase) bioassay, which might be a useful methodology for screening antihyperglycaemic substances. All the flavonoids assayed showed an inhibitory effect on the intact microsomal G-6-Pase: quercetin and kaempferol exhibited the lowest effect; astilbin, quercetin 3-O-alpha-rhamnoside, kaempferol 3-O-alpha-rhamnoside and quercetin 3-O-alpha-arabinoside an intermediate effect. The highest inhibitory activity was shown by quercetin 3-O-alpha-(2''-galloyl)rhamnoside and kaempferol 3-O-alpha-(2''galloyl)rhamnoside. None of the flavonoids mentioned above showed an inhibitory effect on the disrupted microsomal G-6-Pase. Quercetin 3-O-alpha-(2''-galloyl)rhamnoside and kaempferol 3-O-alpha-(2''-galloyl)rhamnoside exhibited the lowest IC50 of all the flavonoids assayed. Also, the phlorizin IC50 is reported.

Inhibition of hepatic neoglucogenesis and glucose-6-phosphatase by quercetin 3-O-alpha(2''-galloyl)rhamnoside isolated from Bauhinia megalandra leaves.

In intact microsomes, quercetin 3-O-alpha-(2''-galloyl)rhamnoside (QGR) inhibits glucose-6-phosphatase (G-6-Pase) in a concentration-dependent manner. QGR increased the G-6-Pase K(m) for glucose-6-phosphate without change in the V(max). The flavonol did not change the kinetic parameters of disrupted microsomal G-6-Pase or intact or disrupted microsomal G-6-Pase pyrophosphatase (PPase) activity. This result allowed the conclusion that QGR competitively inhibits the glucose-6-phosphate (G-6-P) transporter (T1) without affecting the catalytic subunit or the phosphate/pyrophosphate transporter (T2) of the G-6-Pase system.QGR strongly inhibits the neoglucogenic capacity of rat liver slices incubated in a Krebs-Ringer bicarbonate buffer, supplemented with lactate and oleate saturated albumin. The QGR G-6-Pase inhibition might explain the decrease in the liver slice neoglucogenic capacity and, in turn, could reduce glucose levels in diabetic patients.

Thioacetamide effects on the polypeptidic and nucleoporin pattern and chemical composition of rat liver nuclear envelope subfractions

The effect of the administration of seven doses of the hepatocarcinogen thioacetamide on the chemical composition of rat liver nuclear envelope subfractions: associated chromatin, nuclear membranes and pore complex-lamina fraction, is analyzed. No alteration in DNA, RNA or phospholipid content is observed after the hepatocarcinogen treatment. Electrophoretic studies of each subfraction from thioacetamide treated rats show differences in the relative proportions of some polypeptides when compared with the controls. Examination of the wheat germ agglutinin binding polypeptides of each subfraction reveals a decrease in the stain of two pore complex-lamina nucleoporins of 85 and 164 kDa and an increase in one of 93 kDa; this observation can be due to changes in the quantity and/or in the agglutinin binding capacity of the nucleoporin as a result of thioacetamide administration. In view of the participation of nucleoporins in the nucleocytoplasmic transport, the changes observed suggest a relationship between changes of some O-linked N-acetyl glucosamine polypeptides components of the nuclear pore complex and the altered transport of some RNA species observed after thioacetamide administration.

Metabolismo de la glucosa durante la intoxicación con tiocetamida / The metabolism of the glucose during poisoning with thioacetamide

Se describe un método usando el cual se logró purificar parcialmente la glucosa-6-fosfatasa de envoltura nuclear (E.N.) de hígado de rata, mediante el cual se incrementó unas 300 veces la actividad específica de la enzima y se recuperó aproximadamente el 1,2% de la actividad presente en el homogeneizado. El tratamiento con tioacetamida (TAA) no modificó el factor de purificación, el porcentaje de recuperación ni el KM para la glucosa-6-P pero sí disminuyó en cerca de un 50% la VMax de la glucosa-6-Fosfatasa. La administración de TAA produjo glucosuria y fosfaturia sin hiperglicemia ni incremento en la eliminación, Na+, K+, así como tampoco cambios en el pH urinario. De igual manera se observó un efecto hipotensor y una disminución en la velocidad de filtracion glomerular (VFG) de aproximadamente un 42%. La transferencia máxima y el umbral renal para la glucosa fueron disminuidos en aproximadamente un 40 y 75% respectivamente luego de la administración de la droga. Los valores cinéticos del transportador renal de glucosa, dependiente del Na+, también fueron afectados por la administración de TAA, caracterizados por una disminución del KM, la Vmax y del pico de captación de glucosa por vesículas de borde ciliado renal. Por último, se observó en rebanadas de hígado de ratas tratadas con TAA un incremento de 3,5 veces la capacidad neoglucogénica. De los resultados anteriores se concluye que la TAA produce glucosa renal afestando el transportador Na+ glucosa, que la glicemia se mantiene constante a pesar de la glucosuria gracias al incremento en la neoglucogénesis hepática y que la glucosa-6-fosfatasa..

Efecto de la Tioacetamida sobre la envoltura nuclear de las células de la corteza renal de la rata / Thioacetamide effects on the nuclear envelope from rat kidney cortex

Se determinó el efecto que produce la administración de Tioacetamida (TAA) sobre la composición y propiedades de los núcleos y envoltura nuclear (EN) purificados de la corteza renal (CR) de ratas, en relación a preparaciones obtenidas de animales controles a través de un método para la obtención de la EN, cuya pureza relativa fue analizada por microscopía electrónica y métodos enzimáticos. En la fracción nuclear de los animales tratados con TAA, se observaron las siguientes alteraciones: aumento en la concentración de RNA y fosfolípidos (pg/Núcleo) en un 77%, un leve incremento de DNA (pg/Núcleo) en un 17%. Por otro lado la concentración de proteínas (pg/Núcleo) permaneció constante. En la EN se encontró que la concentración de DNA disminuyó en un 68% y la de fosfolípidos en un 37%; en cambio la concentración de RNA aumentó discretamente en un 11%. Se encontraron importantes diferencias al estudiar el patrón polipeptídico obtenido al realizar electroforesis en geles de poliacrilamida de EN preparadas a partir de hígado y CR de ratas controles y tratadas con TAA. La actividad específica de la enzima glucosa-6-fosfatasa en los núcleos y EN de los animales tratados con TAA disminuyó en 54% y 43% respectivamente. En los estudios cinéticos se encontró que por efecto de la droga de la Vmax disminuyó significativamente sin alteración del Km. Se discuten las implicaciones de estos resultados