Calcium influx mediated vasoconstriction: studies in patients with mild and moderate essential hypertension

The forearm vascular resistance (FVR) following intra-arterial infusions of the calcium influx inhibitors nicardipine and verapamil and sodium nitroprusside was compared to that following 10 min arterial occlusion in 10 normotensive (NT) individuals aged 45 +/- 12 years, 12 patients with mild essential hypertension (EH) aged 42 +/- 14 years and 11 patients with moderate EH aged 49 +/- 11 years. Forearm blood flow was measured by venous occlusion plethysmography and resistance was calculated as mean intra-arterial blood pressure/forearm blood flow. The minimal vascular resistance following arterial occlusion was greater in mild EH than in NT and still greater in moderate EH. The minimal vascular resistance to sodium nitroprusside and verapamil was comparable in the three groups. In moderate EH the minimal resistance to nicardipine and verapamil was lower than that following arterial occlusion. When adjusted for the decrease in vascular resistance to arterial occlusion the decrease in resistance to nicardipine and verapamil was greater in moderate EH compared with NT and mild EH but this was not the case for sodium nitroprusside. These findings support the concept of an enhanced calcium influx mediated vasoconstriction in the established phase of essential hypertension but they do not indicate that this is a primary pathogenetic mechanism for the development of essential hypertension.