Renal vasomotion in essential hypertension: influence of vasodilators.

To assess factors responsible for phasic behavior of renal blood flow in essential hypertension, we applied an analytic method based on the estimation of power spectral density to xenon transit through the kidney and examined the renal vasodilator response to a range of agents in 53 normal subjects and 53 patients with essential hypertension. The renal vasodilator response to the calcium channel blocking agent diltiazem, but not the response to alpha-adrenergic blockade (phentolamine) or angiotensin converting enzyme inhibition (teprotide or captopril), was associated with a significant reduction in the amplitude of renal vasomotion. Acetylcholine, a vasodilator that acts through the release of a vasorelaxant factor or factors from endothelium, induced an unanticipated increase in renal vasomotion. These observations further dissociate factors responsible for basal renal vascular tone and periodic changes in renal vascular tone and raise the possibility that abnormalities in the flux of calcium into renal arterioles contribute to increased renal vasomotion in essential hypertension.