Sarcolemmal dependence of isosorbide dinitrate-induced relaxation of aortic smooth muscle.

Studies were conducted to determine if ISDN antagonizes the contractile responses to calcium of chemically-skinned aortic smooth muscle preparations. Isosorbide dinitrate relaxed intact aortic smooth muscle segments in a dose-dependent manner (0.01-100 microM). At all concentrations tested, ISDN was unable to relax triton-skinned smooth muscle preparations. However, the tension development of skinned preparations was inhibited by trifluoperazine (10 microM), a calmodulin antagonist. These results suggest that the relaxation of intact aortic smooth muscle preparations induced by ISDN is not related to an interference with calmodulin-dependent contractile events.