NONSPECIFIC STIMULATORY EFFECTS OF MASTOPARAN ON PANCREATIC-ISLET NUCLEOSIDE DIPHOSPHOKINASE ACTIVITY - DISSOCIATION FROM INSULIN-SECRETION

We examined whether mastoparan (MAS)-induced insulin secretion might i nvolve the activation of nucleoside diphosphokinase (NDP kinase), whic h catalyzes the conversion of GDP to GTP, a known permissive factor fo r insulin secretion. MAS and MAS 7 (which activate GTP-binding protein s), but not MAS 17 (an inactive analog), stimulated insulin secretion from normal rat islets. In contrast to their specific effects on insul in secretion, MAS, MAS 7 and MAS 17 each stimulated formation of the p hosphoenzyme-intermediate of NDP kinase, as well as its catalytic acti vity. These effects were mimicked by several cationic drugs. Thus, cau tion is indicated in using MAS to study cellular regulation, since som e of its effects appear to be non-specific, and may be due, in part, t o its amphiphilic, cationic nature.