Effect of ATP-Dependent K+ Channel Openers and Blockers on Serum Concentration of Aldosterone in Rats

There are many reports for involvement of ATP-sensitive potassium channels in pancreatic, cardiac and vascular smooth muscle cells. This study examined the effect of single doses of K+ channel openers diazoxide, minoxidil and K+ channel blockers chlorpropamide, glibenclamide on serum concentration of aldosterone in male rats. Blood samples were obtained 60 minutes after drug treatment and serum aldosterone level was determined by RIA. The basal serum aldosterone was 659.32 ± 71.48 pg/ml and after diazoxide or minoxidil administration increased to 1188.53 ± 99.45 pg/ml and 1392.69 ± 177.83 pg/ml, respectively. Chlorpropamide or glibenclamide treatment did not produce any change in basal serum aldosterone concentration, but in early streptozotocin-induced diabetic rats decreased serum aldosterone level significantly (P<0.001). Pretreatment with glibenclamide blocked aldosterone response to diazoxide but did not affect aldosterone response to exogenous ACTH to the same extent. Effect of diazoxide in insulin-treated rats was approximately similar to that of normal rats. Comparison of blood glucose concentration determined in normal, insulin treated and diabetic rats after different drug administration showed that there is no correlation between blood glucose level and the responses observed in serum hormone concentration. The results indicate that regulatory processes involved in the secretion of aldosterone are responsive to drugs affecting glibenclamide–sensitive K+ channels