Effect of ghrelin on glucose-stimulated insulin secretion from MIN6 cells. (A) Medium insulin concentration after 60-min incubation of MIN6 in the presence of 3.3 (□) or 22.2 (▪) mmol/liter glucose with 0.1, 1, or 10 nmol/liter or without ghrelin. Insulin concentration was measured by ELISA. All values are expressed as the means ± SDs of three independent experiments (n = 9–15, *, P < 0.05 vs. nonstimulation with ghrelin at 22.2 mmol/liter glucose). (B) Insulin secretion with 3.3 (□) or 22.2 (▪) mmol/liter glucose containing with 10 nmol/liter or without ghrelin for the indicated times. Results are expressed as the means ± SDs of three independent experiments (n = 5–7; *, P < 0.05; **, P < 0.01 vs. nonstimulation with ghrelin at same times).