BRAZILIN INHIBITS ACTIVITIES OF PROTEIN-KINASE-C AND INSULIN-RECEPTORSERINE KINASE IN RAT-LIVER

Hypoglycemic action of brazilin was found to be based on the improveme nt of peripheral glucose utility, and this action might be correlated with the insulin action pathway. In the present study we investigated the effect of brazilin on the insulin receptor autophosphorylation pro tein kinase C (PKC), protein phosphatase and insulin receptor serine k inase in order to confirm whether the hypoglycemic mechanism is concer ned with insulin action pathway. Brazilin was found to inhibit PKC and insulin receptor serine kinase, which are involved in the regulation of insulin signal pathway. But any significant effect was not shown on insulin receptor tyrosine kinase activity, autophosphorylation and ph osphatase activity. These findings suggest that brazilin might enhance insulin receptor function by decreasing serine phosphorylation, which might mediate hypoglycemic effect of brazilin.