Inhibition of insulin secretion by GA is not iNOS-mediated. (A) Rat islets were incubated for 24 h at 37°C with 0.1 mg/mL HA (white bar) or GA (black bar), in the presence of the inhibitor of nitric oxide synthetase, L-NAME, at 1 mM, or the selective inhibitor of iNOS, AG, at 2 mM, under the G3 or G15 condition. Each bar represents the mean plus SEM of 3 separate experiments, each with n = 5. (B) Real-time PCR was performed with cDNA from RNA that had been isolated from HA- or GA-treated rat islet cells. t-value is the relative amount of iNOS-mRNA to β-actin-mRNA. (C) Rat islets were incubated for 24 h at 37°C with 0.1 mg/mL HA or GA, and the proteins isolated from islet cells were stained with anti-β-actin or anti-iNOS antibody.