Figure 4.

PKA inhibitor H-89 fails to abrogate the action of 8-pCPT-2'-O-Me-cAMP-AM to potentiate GSIS in adult male C57BL/6J mouse islets. Illustrated are findings obtained in static incubation assays using methodologies of islet isolation and solution exposure described previously.¹³ Islets were exposed to KRB containing 2.8 mM glucose for 30 min and were then exposed to KRB containing 20 mM glucose with or without added test substances. These test substances included H-89 (10 µM), dibutyryl-cAMP-AM (Db-cAMP-AM; 10 µM), and 8-pCPT-2'-O-Me-cAMP-AM (ESCA-AM; 10 µM). Each test substance was disolved in a vehicle solution comprised of KRB containing 0.1% DMSO and 0.1% BSA. The findings are representative of a single experiment repeated twice. Values of fold-stimulation were calculated by comparing insulin secretion measured in 20 mM glucose KRB relative to KRB containing 2.8 mM glucose. Values are mean ± s.e.m. for duplicate determinations. Statistical significance was evaluated by the t-test (*p < 0.05).