AUGMENTATION OF BARORECEPTOR REFLEX FUNCTION BY ORAL CALCIUM SUPPLEMENTATION IN ESSENTIAL HYPERTENSION

Abstract

1. We studied the effect of oral calcium supplementation (1.0 g/day) for 1 week on baroreceptor reflex function and the lability of blood pressure in association with the changes in autonomic nervous activity in 14 hospitalized patients with mild to moderate essential hypertension (nine males and five females, mean age of 56 +/- 11.2 (s.d.) years). 2. Baroreceptor reflex sensitivity (BRS) was determined by the change in R-R intervals in response to the pressor response induced by phenylephrine injection. We measured coefficient of variation of R-R interval (CVR-R) and urinary excretion of catecholamines to evaluate the mechanism of change in BRS. We also used coefficient of variation of blood pressure (CVBP) and error of single cosinor analysis as parameters for lability of 24-h blood pressure. 3. The means of 24-h systolic and diastolic blood pressures showed no significant changes after calcium supplementation for 1 week. BRS and CVR-R were significantly increased by calcium supplementation. Daily excretions of norepinephrine and epinephrine corrected by creatinine were unchanged. Both CVBP and error of 24-h systolic blood pressure showed a significant decrease after calcium treatment. 4. These results indicate that oral calcium supplementation augments baroreceptor reflex function, in part through an enhancement of parasympathetic nervous activity, resulting in reduction of the lability of blood pressure in patients with mild to moderate essential hypertension.