Enhanced activation of phospholipase C and insulin secretion from islets incubated in fatty acid–free bovine serum albumin

• Published in: Metabolism, clinical and experimental Vol. 57; no. 2; pp. 290 - 298
• Main Authors: Zawalich, Walter S, Zawalich, Kathleen C
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.02.2008; Elsevier
• Subjects: Animals; Biological and medical sciences; Carbachol - pharmacology; Cholinergic Agonists - pharmacology; Diazoxide - pharmacology; Endocrinology & Metabolism; Enzyme Activation - drug effects; Feeding. Feeding behavior; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Inositol - metabolism; Insulin - metabolism; Insulin Secretion; Islets of Langerhans - drug effects; Islets of Langerhans - enzymology; Islets of Langerhans - metabolism; Male; Mice; Potassium Chloride - pharmacology; Rats; Rats, Sprague-Dawley; Serum Albumin, Bovine - pharmacology; Tetradecanoylphorbol Acetate - pharmacology; Type C Phospholipases - metabolism; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Pancreatic hormone; Bovine; Enzyme; Secretion; Langerhans islet; Albumin; Lipids; Esterases; Activation; Phosphoric diester hydrolases; Fatty acids; Insulin; Phospholipase C; Vertebrata; Mammalia; Hydrolases; Serum; Artiodactyla; Ungulata; Endocrinology; Endocrine pancreas
• ISSN: 0026-0495; 1532-8600
• DOI: 10.1016/j.metabol.2007.09.015

Abstract Incubation in 100 μ mol/L fatty acid–free bovine serum albumin (FAF-BSA) significantly amplifies insulin secretion from isolated, perifused rat islets. When compared with the responses of control islets incubated in 100 μ mol/L radioimmunoassay-grade BSA, insulin secretion rates were increased 2- to 3-fold when these islets were stimulated with 10 mmol/L glucose alone or with the combination of 10 mmol/L glucose, 15 mmol/L KCl, and 100 μ mol/L diazoxide. These amplified secretory responses were paralleled by significant increases in the phospholipase C (PLC) activation monitored by fractional increases in3 H-inositol efflux from these same islets. Amplified PLC responses were also observed with the cholinergic agonist carbachol (50 μ mol/L). No differences in the secretory responses to the protein kinase C activator phorbol 12-myristate 13-acetate (200 nmol/L) could be detected between control and FAF-BSA–pretreated rat islets. Mouse islets were also immune to the amplifying impact of this treatment protocol. These findings demonstrate that short-term incubation in FAF-BSA significantly augments the activation of PLC in rat islets by a number of agonists. This proximal event provides the impetus for the distal activation of protein kinase C. If applicable to human islets, this manipulation may provide a mechanism to enhance the secretory responses from islets destined for transplantation, thus improving their in vivo secretory capacity.