RESUMO
1. Intestinal brush border membrane vesicles (BBMV) were prepared from 3-week-old broiler chickens. 2. Electron microscopy of the BBMV fraction showed single membrane vesicles of different sizes with no electron dense material inside. No other organelles were observed. The sucrase and maltase activities were enriched by factors of 16 and 18, respectively, in the BBMV fraction in comparison with the homogenate. On the other hand, the Na+/K+-ATPase sensitivity to ouabain was increased by a factor of 0.8. 3. The BBMV showed a maximum L-[14C]-arginine uptake (944.9 +/- 22.9 pmoles/mg protein) at 45 s and thereafter it declined slowly. In the presence of 0.5 mM L-canavanine, the L-[14C]-arginine uptake by BBMV was reduced by 43.6% at 45 s. 4. It is concluded that L-canavanine inhibits L-arginine Na+-dependent transport across the enterocyte apical membrane in a highly purified intestinal BBMV from broiler chickens.
Assuntos
Arginina/metabolismo , Canavanina/farmacologia , Absorção Intestinal/efeitos dos fármacos , Mucosa Intestinal/metabolismo , Microvilosidades/metabolismo , Animais , Arginina/antagonistas & inibidores , Biomarcadores , Radioisótopos de Carbono , Fracionamento Celular , Galinhas , Mucosa Intestinal/efeitos dos fármacos , Cinética , Microvilosidades/efeitos dos fármacos , Microvilosidades/ultraestrutura , Técnica de Diluição de RadioisótoposRESUMO
Aqueous extract of Bauhinia megalandra leaves was able to inhibit the intestinal glucose absorption in a concentration-dependent way and additive to phlorizine. Moreover, B. megalandra leaf extract drastically reduced the 14C-glucose uptake by enterocyte brush border membrane vesicles. The B. megalandra leaf extract administrated orally, simultaneously with glucose improved the glucose tolerance with a significant reduction of the 30-min peak. The extract did not have an effect on the glucose tolerance when glucose was administrated subcutaneously.
Assuntos
Bauhinia , Glucose/metabolismo , Hipoglicemiantes/farmacologia , Absorção Intestinal/efeitos dos fármacos , Fitoterapia , Extratos Vegetais/farmacologia , Administração Oral , Animais , Radioisótopos de Carbono/metabolismo , Diabetes Mellitus/prevenção & controle , Glucose/administração & dosagem , Teste de Tolerância a Glucose , Hipoglicemiantes/administração & dosagem , Hipoglicemiantes/uso terapêutico , Intestino Delgado/efeitos dos fármacos , Intestino Delgado/metabolismo , Masculino , Microvilosidades/efeitos dos fármacos , Microvilosidades/metabolismo , Extratos Vegetais/administração & dosagem , Extratos Vegetais/uso terapêutico , Folhas de Planta , Ratos , Ratos Sprague-DawleyRESUMO
En microsomas intactos, dos flavonas purificadas a partir de hojas de Bauhinia megalandra, inhiben la actividad de la glucosa 6-fosfatasa en una manera dependiente de su concentración. Ambas flavonas incrementan el valor del Km para glucosa-6-fosfato, sin modificar el valor de Vmax. Los resultados permiten concluir que ambas flavonas inhiben competitivamente al transportador de glucosa-6-fosfato (T1), sin afectar ni a la subunidad catalítica ni al transportador de fosfato/pirofosfato (T2) del sistema de la glucosa-6-fosfatasa. Las flavonas inhiben la capacidad neoglucogénica de rebanadas de hígado incubadas en buffer Krebs-Ringer bicarbonato suplementado con lactato y albúmina saturada con oleato. La inhibición que ejercen las flavonas sobre el transportador T1 del sistema de la glucosa-6-fosfatasa microsomal, puede explicar la disminución de la capacidad neoglucogénica de las rebanadas de hígado, lo cual podría reducir la concentración de glucosa en pacientes diabéticos
Assuntos
Humanos , Animais , Masculino , Feminino , Flavonas , Glucose-6-Fosfatase , Ácido Oleico , Bioquímica , VenezuelaRESUMO
A total of 21 extracts derived from 17 different plant species collected in Venezuelan Amazons have been tested for the following biological activities: cardiovascular activity, brine shrimp lethality, and inhibitory effects on the hydrolysis of glucose-6-phosphate in intact and disrupted microsomes. Eight extracts diminished rat blood pressure with or without changes in heart rate. The fruit extract of Swartzia leptopetala and the leaf and twig extract of Connarus lambertii resulted in death of experimental animals. The majority of extracts (17 extracts) showed significant toxicity against Artemia salina. Concerning the hydrolysis of glucose-6-phosphate, better inhibitory effects were observed in intact microsomes than in disrupted ones for all the extracts, suggesting that these extracts intervene with variable potency in glucose-6-phosphate transport through the microsomal membrane.
Assuntos
Fármacos Cardiovasculares/farmacologia , Extratos Vegetais/farmacologia , Plantas Medicinais/química , Animais , Artemia/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Avaliação Pré-Clínica de Medicamentos , Feminino , Glucose-6-Fosfato/antagonistas & inibidores , Glucose-6-Fosfato/metabolismo , Frequência Cardíaca/efeitos dos fármacos , Masculino , Microssomos/metabolismo , Extratos Vegetais/química , Extratos Vegetais/toxicidade , Estruturas Vegetais/química , Estruturas Vegetais/toxicidade , Plantas Medicinais/classificação , Ratos , Ratos Sprague-Dawley , Testes de Toxicidade , VenezuelaRESUMO
1. The hepatic glucose-6-phosphatase (G-6-Pase) kinetic variables from chickens were studied in intact and disrupted microsomes using two substrates: glucose-6-phosphate (G-6-P) and pyrophosphate (PPi). They were studied from embryonic life to 51 d of age. 2. The phosphohydrolase activity studied in the broiler chicken liver microsomes corresponds to a true glucose-6-phosphatase. 3. The enzyme VMAX with both substrates in intact and disrupted microsomes showed 2 maxima: one in 19-d-old embryos and the other in 9-d-old chickens. Pyrophosphatase (PPase) VMAX in intact microsomes was higher than that of the G-6-Pase at all ages studied, except in 12 d embryos and 3-d-old chicks. In disrupted microsomes the VMAX of both enzymatic activities were similar. The G-6-Pase latency was high in the 19-d-old embryos and 51-d-old chickens. 4. The KM for PPi and G-6-Pase decreased when microsomes were disrupted. In intact microsomes the G-6-P KM was low in embryos and 3-d-old chicks and later increased. On the other hand, the PPi KM in intact microsomes showed little change during the animal's life and was lower than that of G-6-P. In disrupted microsomes the KM for both substrates were similar. 5. These results suggest a sequential incorporation of the G-6-Pase system components in the endoplasmic reticulum.
Assuntos
Embrião de Galinha/metabolismo , Galinhas/metabolismo , Difosfatos/farmacocinética , Glucose-6-Fosfatase/farmacocinética , Microssomos Hepáticos/enzimologia , Envelhecimento , Animais , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/metabolismo , Consumo de Oxigênio , Monoéster Fosfórico Hidrolases/metabolismoRESUMO
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.