Flow resistance and its components in hypertensive men treated with the calcium antagonist isradipine.

The components of blood flow resistance were investigated in 14 men with essential hypertension (diastolic blood pressure higher or equal to 100 mm Hg) before and after treatment with the dihydropyridine calcium antagonist-isradipine. Isradipine reduced intraarterial blood pressure by decreasing the total (placebo 5.1 U.mPa-1.s-1; isradipine 3.9 U.mPa-1.s-1), and renal (placebo 48.9 U.mPa-1.s-1, isradipine 35.4 U.mPa-1.s-1) vascular hindrance, the blood viscosity being unchanged. Arterial compliance was increased by isradipine (placebo 1.03 ml.mmHg-1; isradipine 1,25 ml.mmHg-1). The pressor response to adrenergic alpha stimulation with phenylephrine was decreased during treatment with the calcium antagonist. The compliance of the venous system was not changed by the treatment with isradipine. Haemorheological parameters were stable throughout the study but some changes in the correlations between the different rheological parameters were observed. The present study indicates that the antihypertensive effect of the dihydropyridine calcium antagonist isradipine was the result of functional modulation of the small and large arteries, the venous system and the flow properties of blood being unaffected.