Suramin inhibits glucose-induced Ca2+ response in single rat pancreatic beta cells

It is reported that glucose releases ATP with insulin from pancreatic beta cells. Suramin (50-200 microM), a purinoceptor blocker, reversibly and dose-dependently inhibited the rise in cytoplasmic calcium concentration ([Ca2+]i) induced by glucose and by ATP in single beta cells. Suramin did not inhibit the glucose-induced increase in NAD(P)H fluorescence. The rise in [Ca2+]i induced by tolbutamide (an inhibitor of ATP-sensitive K+ channels), arginine (a cationic amino acid) and acetylcholine was unaffected by suramin (50-200 microM). This suggests that suramin inhibits the glucose-induced Ca2+ response without an inhibitory effect on glucose metabolism, K+ channels, voltage-dependent Ca2+ influx or Ca2+ release from internal Ca2+ stores and that a purinergic mechanism is involved in the glucose response in beta cells.