Effects of Glucose, Exogenous Insulin, and Carbachol on C-peptide and Insulin Secretion from Isolated Perifused Rat Islets

• Published in: The Journal of biological chemistry Vol. 277; no. 29; pp. 26233 - 26237
• Main Authors: Zawalich, Walter S., Zawalich, Kathleen C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.07.2002; American Society for Biochemistry and Molecular Biology
• Subjects: Androstadienes - pharmacology; Animals; C-Peptide - metabolism; Carbachol - administration & dosage; Carbachol - pharmacology; Cattle; Cells, Cultured; Dose-Response Relationship, Drug; Genistein - pharmacology; Glucose - administration & dosage; Glucose - pharmacology; Humans; Insulin - administration & dosage; Insulin - metabolism; Insulin - pharmacology; Insulin Secretion; Islets of Langerhans - drug effects; Islets of Langerhans - metabolism; Male; Rats; Rats, Sprague-Dawley; Wortmannin
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M202291200

Isolated perifused rat islets were stimulated with glucose, exogenous insulin, or carbachol. C-peptide and, where possible, insulin secretory rates were measured. Glucose (8–10 mm) induced dose-dependent and kinetically similar patterns of C-peptide and insulin secretion. The addition of 100 nm bovine insulin had no effect on C-peptide release in response to 8–10 mm glucose stimulation. The addition of 100 nm bovine insulin or 500 nm human insulin together with 3 mm glucose had no stimulatory effect on C-peptide secretion rates from perifused rat islets. Stimulation with carbachol plus 7 mm glucose enhanced both C-peptide and insulin secretion, and the further addition of 100 nm bovine insulin had no inhibitory effect on C-peptide secretory rates under this condition. Perifusion studies using pharmacologic inhibitors (genistein and wortmannin) of the kinases thought to be involved in insulin signaling potentiated 10 mm glucose-induced secretion. The results support the following conclusions. 1) C-peptide release rates accurately reflect insulin secretion rates from collagenase-isolated, perifused rat islets. 2) Exogenously added bovine insulin exerts no inhibitory effect on release to several agonists including glucose. 3) In the presence of 3 mm glucose, exogenously added bovine or human insulin do not stimulate endogenous insulin secretion.