Cyclosporine A inhibits relaxation but does not induce vasoconstriction in human subcutaneous resistance vessels

The effects of cyclosporine on the functional characteristics of human subcutaneous resistance vessels were investigated. Resistance vessels were obtained from normal subjects undergoing routine surgery. Incubation with cyclosporine did not alter the resting tone of the vessels, but decreased the maximum contractile response and the sensitivity of the vessels to stimulation with exogenous noradrenaline and potassium. Cyclosporine decreased the rate of spontaneous relaxation and inhibited endothelium-dependent relaxation as assessed by the response to acetylcholine. Paradoxically, endothelium-independent relaxation as assessed by the response to sodium nitroprusside was augmented. Hypertension induced by cyclosporine may, in part, be explained by a reduction in relaxation of peripheral resistance vessels.