Verapamil-induced vasodilation is enhanced in essential hypertension

The dependency of arteriolar tone on calcium influx was studied in 11 patients with essential hypertension (EHT) and compared to 11 age-matched normotensive (NT) subjects by measuring the forearm blood flow (FAF) response to intraarterial infusion of the calcium channel blocker verapamil (Verap) and the nonspecific vasodilator sodium nitroprusside (Nip) with venous occlusion plethysmography. Verap in incremental dosages induced a greater increase in forearm blood flow (delta FAF) in EHTs than in NTs, whereas there was no significant difference in delta FAF following Nip. When delta FAF to Verap was adjusted for delta FAF to Nip, it was still greater in EHTs. In EHTs delta FAF to all dosages of Verap correlated positively with basal plasma epinephrine concentration, and at the two highest dosages of Verap, associated with a decrease in systemic blood pressure, it correlated negatively with plasma renin activity and plasma angiotensin II concentration. Thus, increased dependency of arteriolar tone on calcium influx is related to the activity of the sympathetic nervous system in EHT. This association may be due to a common derangement in transmembranous ionic fluxes in the vascular smooth muscle cells and sympathetic neurons in EHT.