Suramin Inhibits Glucose-Induced Ca²⁺ Response in Single Rat Pancreatic β Cells

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It is reported that glucose releases ATP with insulin from pancreatic βcells. Nuramin (50-200μM), a purinoceptor blocker, reversibly and dose-dependently inhibited the rise in cytoplasmic calcium concentration ([Ca²⁺]_i) induced by glucose and by ATP in single β 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 μM). 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 β cells.