Abstract
1 The intent of this study was to determine whether or not increased calcium-influx-mediated vasoconstriction is a primary pathogenetic disturbance in essential hypertension.
2 Ten normotensive subjects (NT) (aged 45 ± 12 years) and 23 patients with essential hypertension (EH) were studied. Twelve of the patients (aged 42 ± 12 years) were classified as having mild EH and 11 patients (aged 49 ± 11 years) as having moderate EH.
3 Forearm blood flow and intra-arterial blood pressure were measured. Forearm vascular resistance (FVR) was calculated under basal conditions, during reperfusion following 10 min arterial occlusion, and after infusion into the brachial artery of sodium nitroprusside (0.15 and 0.6 μg min-1 100 ml-1 tissue for 2 min each) and the calcium-influx inhibitors nicardipine (5 and 40 μg min-1 100 ml-1 tissue for 1 min each) and verapamil (80 μg min-1 100 ml-1 tissue for 1 min).
4 FVR after 10 min arterial occlusion was lower in mild EH than in moderate EH and still lower in NT. FVR was comparable in the three groups following infusion of maximal doses of sodium nitroprusside, nicardipine, and verapamil.
5 To allow for the vasodilator response to arterial occlusion, the decrease in FVR measured after each drug was divided by that obtained after arterial occlusion in each individual. The adjusted vasodilator response to nicardipine and verapamil, but not to sodium nitroprusside, was greater in moderate EH than in NT and mild EH. In the latter two groups the adjusted vasodilator responses were comparable.
6 Calcium-influx mediated vasoconstriction is thus enhanced in moderate (established) EH but not in mild EH and, therefore, is unlikely as a primary pathogenetic disturbance in essential hypertension.
Keywords: hypertension, nicardipine, vasodilatation, verapamil
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