RESUMO
Gastric inhibitory peptide release into the portal vein in response to duodenal infusion of D-glucose was studied in the presence of a leaf extract of Gymnema sylvestre, purified gymnemic acid and inhibitors of some putative glucose sensors and carriers in the intestinal lumen. Intraduodenal infusion of D-glucose significantly increased the portal immunoreactive gastric inhibitory peptide concentration in a dose-dependent manner. The increase in the portal immunoreactive gastric inhibitory peptide induced by glucose was significantly depressed by concomitantly infused leaf extract of Gymnema sylvestre, purified gymnemic acid and phlorizin but not by cytochalasin B. Mannoheptulose, which inhibits glycolysis, and procaine and lidocaine, which inhibit the vagal glucoreceptor in the lumen, did not affect portal immunoreactive gastric inhibitory peptide concentrations. These results suggest that a glucose receptor, which interacts with the leaf extract of Gymnema sylvestre, purified gymnemic acid and phlorizin, exists for the release of immunoreactive gastric inhibitory peptide and that the glucose receptor for gastric inhibitory peptide release is not likely to be identical with a glucose transporter or a vagal glucoreceptor in the lumen.
Assuntos
Polipeptídeo Inibidor Gástrico/metabolismo , Glucose/farmacologia , Extratos Vegetais/farmacologia , Saponinas , Triterpenos/farmacologia , 3-O-Metilglucose , Animais , Citocalasina B/farmacologia , Desoxiglucose/farmacologia , Duodeno/efeitos dos fármacos , Polipeptídeo Inibidor Gástrico/sangue , Glucose/administração & dosagem , Glibureto/farmacologia , Cinética , Masculino , Manoeptulose/farmacologia , Metilglucosídeos/farmacologia , Florizina/farmacologia , Veia Porta , Ratos , Ratos WistarRESUMO
1. A new substance that suppressed selectively the neural responses of the rat to sweet taste stimuli was isolated from the leaves of Gymnema sylvestre. 2. The substance was proved to be a peptide consisting of 35 amino acids and having a molecular weight of about 4,000. 3. The inhibitory effect on the sweet responses appeared after treating the tongue surface with the peptide at a concentration of more than 1 x 10(-6) M.
Assuntos
Proteínas de Plantas/farmacologia , Plantas Medicinais/química , Paladar/efeitos dos fármacos , Animais , Nervo da Corda do Tímpano/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Eletroforese em Gel de Poliacrilamida , Feminino , Japão , Espectroscopia de Ressonância Magnética , Proteínas de Plantas/isolamento & purificação , Plantas Medicinais/anatomia & histologia , Ratos , Ratos EndogâmicosRESUMO
1. One of the fractions obtained from the extract of Zizyphus jujuba leaves suppressed the response of the chorda tympani to sucrose, both in the rat and hamster. 2. In the rat and man, suppressive effect was found to be significant in responses to various sugars and artificial sweeteners but not in some sweet amino acids.