Protein phosphorylation is required for diazoxide to open ATP‐sensitive potassium channels in insulin (RINm5F) secreting cells

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Abstract
The patch‐clamp open‐cell recording configuration has been used to investigate the effects of non‐hydrolyzable analogues of ATP on the diazoxide‐activation of KATP channels in the insulin‐secreting cell line RINm5F. K+ channels inhibited by 0.1, 0.5 and 1.0 mM ATP were consistently activated by 200 μM diazoxide. During sustained activation of channels, exchange of ATP for either AMP‐PNP, AMP‐PCP or ATPγS abolished the effects of diazoxide. If diazoxide was added to the membrane in the continued presence of AMP‐PNP, AMP‐PCP or ATPγS either no effects were observed or alternatively a small transient activation of channels occurred. This study suggests that protein phosphorylation is necessary for diazoxide to activate ATP‐sensitive potassium channels in insulin‐secreting cells.