Differential effects of Ca2+-calmodulin on adenylate cyclase activity cyclase activity in mouse and rat pancreatic islets.
The effects of Ca2+-calmodulin on adenylate cyclase activity in EGTA-washed, 27000 g particulate fractions of mouse and rat pancreatic islets were studied. Ca2+ (10 microM)-calmodulin (1 microM) stimulated adenylate cyclase activity 53.1 +/- 5.2 (N = 6)% in the particulate fraction of rat islets. Trifluoperazine (50 microM), a specific inhibitor of calmodulin, inhibited the Ca2+-calmodulin activation of the adenylate cyclase activity of this fraction of rat islets. These results confirm previous reports dealing with Ca2+-Calmodulin and rat islet adenylate cyclase [Valverde, Vandermeers. Anjaneyulu & Malaisse (1979) Science 206, 225-227; Sharp, Wiedenkeller, Kaelin, Siegel & Wollheim (1980) Diabetes 29, 74-77]. In contrast, however, Ca2+ (1-100 microM)-calmodulin (1-10 microM) did not stimulate the adenylate cyclase activity in the EGTA-washed particulate fraction of mouse islets, and trifluoperazine (50 microM) did not inhibit the adenylate cyclase activity of this fraction of mouse islets, although some remaining calmodulin [0.18 +/- 0.05 (n = 3) microgram/mg of protein] could be demonstrated. GTP (10 microM) enhanced islet adenylate cyclase activity considerably, but did not confer any sensitivity towards Ca2+-calmodulin on mouse islet adenylate cyclase. The results question the role of calmodulin in the Ca2+-dependent rise in cyclic AMP evoked by glucose in pancreatic islets.
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006160:Guanosine Triphosphate / Q000494:pharmacology; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D051379:Mice; D051381:Rats; D013045:Species Specificity; D014268:Trifluoperazine / Q000494:pharmacology
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D014268:Trifluoperazine; D006160:Guanosine Triphosphate; D000262:Adenylyl Cyclases; D002118:Calcium