The Effects of Calcium Channel Blockade on Blood Pressure and Calcium Metabolism

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Abstract
To study the relation of calcium channel blockade to calcium metabolism, we measured serum ionized calcium (Caio++), magnesium (Mg), calcitonin (CT), and 1,25-dihydroxyvitamin D (1,25-D) before and after short-term therapy with verapamil 120 mg three times daily in essential hypertensive subjects on low (10 mEq) and high (200 mEq) dietary sodium intakes. Salt-sensitive compared with salt-insensitive subjects on high ν low dietary salt intake had lower Caio++ (Ρ < .05), higher 1,25-D (Ρ < .02), and a greater hypertensive responsive to verapamil (%ΔDBP = - 17.7 ν - 8.2, Ρ < .05). The %ΔDBP was related to the initial CT (r = 0.68, Ρ < .05), initial 1,25-D (R = - 0.89, Ρ < .01), and to the drug-induced %Δ1,25 D (R = .60, Ρ < .05). Thus, lower initial calcium and calcitonin levels, higher initial levels of 1,25-D, and a greater drug-induced suppression of 1,25-D were associated with an enhanced hypotensive response to verapamil. Verapamil elevated Caio++ (2.46 ± 0.04 to 2.53 ± 0.04 2.00 mEq/L, Ρ < .05), and suppressed Mg (2.00 ± 0.03 to 1.84 ± 0.03 mEq/L, Ρ < .01) and 1,25-D levels (66.7 ± 8.1 to 51.6 ± 5.7 pg/mL, Ρ < .05). These results suggest interactive effects of sodium and calcium metabolism in essential hypertension, especially among salt-sensitive individuals. We conclude that alterations of calcium metabolism may underlie the sensitivity to verapamil therapy and may contribute to its hypotensive effects. Am J Hypertens 1989;2:927-930

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