title: Protein kinase C and calcium regulation of adenylyl cyclase in isolated rat pancreatic islets.
abstract: Rat islets express several isoforms of adenylyl cyclase (AC), and the regulation of AC activity in isolated islets by Ca(2+) and protein kinase C (PKC) was investigated. At basal 2.8 mmol/l glucose, the muscarinic receptor agonist carbamylcholine chloride (CCh) evoked a concentration-dependent increase in cAMP generation with a maximum increase at least 4.5-fold above control. In contrast, forskolin and glucagon-like peptide 1 fragment 7-36 amide increased cAMP accumulation 23-fold and almost 10-fold, respectively. Cholecystokinin 26-33 sulfated amide (CCK) also stimulated cAMP production by up to eightfold, as did the phorbol ester, phorbol 12,13-dibutyrate (PDBu). PDBu and CCh or CCK responses were not additive. The effects of phorbol ester, CCh, and CCK were inhibited by as much as 75% by the PKC inhibitors GF 109203X and Ro-32-0432 and after PKC downregulation. In the absence of extracellular Ca(2+), PDBu-, CCh-, and CCK-induced cAMP production was inhibited by approximately 50% in each case. Chelation of intracellular Ca(2+) with 1,2-bis(o-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester (BAPTA/AM) inhibited CCh- and CCK-stimulated cAMP generation by approximately 50% but did not inhibit the stimulatory effect of PDBu. Stringent Ca(2+) depletion by removal of extracellular Ca(2+) and inclusion of BAPTA/AM allowed for increased cAMP production in response to CCh and CCK; PKC inhibitors and PKC downregulation prevented this stimulation. Glucose stimulation also increased islet cAMP production, but PDBu did not potentiate the glucose response. The results suggest that Ca(2+) influx, Ca(2+) mobilization, and PKC activation play important roles in the modulation of AC activity in pancreatic islets.
authors.affiliation: Department of Pharmacology and Toxicology, the State University of New York at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, New York 14214, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Tian
authors.forename: S G
authors.initials: SG
authors.lastname: Laychock
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis; D015536:Down-Regulation; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000201:enzymology*; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012844:Sincalide / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D018679:Cholinergic Agonists; D010446:Peptide Fragments; C439758:cholecystokinin (26-33) sulfated amide; D015240:Phorbol 12,13-Dibutyrate; D002217:Carbachol; D000242:Cyclic AMP; D011493:Protein Kinase C; D000262:Adenylyl Cyclases; D012844:Sincalide; D002118:Calcium