Thiazolidinediones are insulin-sensitising agents effective in controlling type II diabetes. These compounds also cause vasodilation. We evaluated the effects of the thiazolidinediones troglitazone and rosiglitazone on the glibenclamide-sensitive K+ current in freshly isolated rat aorta myocytes. Troglitazone inhibited this current in a concentration-dependent manner (IC50 similar to 1 mu M) Rosiglitazone had a similar, but much less potent (IC50 similar to 20 mu M) action. Block of the glibenclamide-sensitive K+ channels, in particular by troglitazone, may potentially affect the response of arteries to hypoxia and to certain endogenous and exogenous vasodilators. (C) 1999 Elsevier Science B.V. All rights reserved.