EFFECTS OF ANTIHYPERTENSIVE THERAPY ON PLATELET CYTOSOLIC CALCIUM RESPONSES TO LOW-DENSITY-LIPOPROTEIN CHOLESTEROL

This study examines the effects of antihypertensive therapy on platele t cytosolic calcium [Ca2+](i) responses to low-density lipoprotein cho lesterol (LDL) and vasopressin (AVP) in 15 patients (50-80 years) part icipating in the Hypertension Optimal Treatment International Study, A ll patients (diastolic blood pressure (DBP) greater than or equal to 1 00 mm Hg and less than or equal to 115 mm Hg) were treated with the ca lcium antagonist felodipine (10 mg po) with or without addition of ena lapril (up to 20 mg daily as needed) to lower diastolic pressures to < 85 mm Hg, This antihypertensive therapy lowered nap (104 +/- 0.8 to 78 +/- 1.6 mm Hg, P < 0.0001), but had no effect on basal [Ca2+](i) or A VP-stimulated [Ca2+](i) responses. Basal platelet [Ca2+](i) following antihypertensive therapy (49 +/- 3.4 ng/ml) were not different from th ose prior to therapy (52 +/- 4.7 ng/ml), Additionally, [Ca2+](i) respo nses to AVP following therapy (554 +/- 74 units) were not different fr om those prior to treatment (595 +/- 49 units), Following antihyperten sive therapy, [Ca2+](i) responses to 200 mu g/ml of LDL were decreased fourfold (P < 0.05). These results suggest that anithypertensive ther apy with a calcium channel blocker may potentially impact the atheroge nic process by reducing the platelet [Ca2+](i) rise, and potentially t he aggregatory response, to LDL.