title: Insulin release independent of a rise in cytosolic free Ca2+ by forskolin and phorbol ester.
abstract: The role of cytosolic free Ca2+ in insulin release was evaluated using isolated rat pancreatic islets permeabilized with digitonin and incubated in Ca-EGTA buffers to fix free Ca2+ concentration at arbitrary levels. Ca2+ induced insulin release in a concentration-dependent manner with the threshold being between 0.1 and 1 microM. The hormone release was increased by forskolin and 12-O-tetradecanoyl phorbol-13-acetate (TPA), a potent activator of adenylate cyclase and that of protein kinase C, respectively. The findings suggest that activation of both protein kinase A and protein kinase C modulate insulin release without a concomitant increase in cytosolic free Ca2+.
authors.forename: T
authors.initials: T
authors.lastname: Tamagawa
authors.forename: H
authors.initials: H
authors.lastname: Niki
authors.forename: A
authors.initials: A
authors.lastname: Niki
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005576:Colforsin; D000242:Cyclic AMP / Q000378:metabolism; D004072:Digitonin / Q000494:pharmacology; D004224:Diterpenes / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010704:Phorbols / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D004224:Diterpenes; D007328:Insulin; D010704:Phorbols; D005576:Colforsin; D000242:Cyclic AMP; D004072:Digitonin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium