ACUTE CARDIOVASCULAR EFFECT OF 1,25-DIHYDROXYCHOLECALCIFEROL IN ESSENTIAL-HYPERTENSION

A role for vitamin D in the pathophysiology of essential hypertension has frequently been suggested, but acute direct effects on blood press ure, cardiac output, renal hemodynamics, or hormones have not previous ly been demonstrated. The rapid effects of 1,25-dihydroxycholecalcifer ol (1,25-D) were assessed over 120 min after a bolus injection (0.02 m u g/kg body weight) in eight men with essential hypertension and in ni ne healthy men. A placebo group of 10 healthy men was also included. I onized calcium was monitored closely during the study, and was kept co nstant with a clamping technique. In the hypertensive patients, a tran sient increase in blood pressure and a reciprocal fall in cardiac outp ut measured by a CO, rebreathing technique (-15%, P <.05) were observe d after 1,25-D injection. In the control group, both blood pressure an d cardiac output remained unchanged. The glomerular filtration rate, e ffective renal plasma now, and urinary sodium and water excretions wer e unchanged in both groups. Plasma levels of atrial natriuretic peptid e at baseline were higher in the hypertensive patients than in the con trol subjects (P <.02); plasma levels of renin, aldosterone, norepinep hrine, endothelin, and parathyroid hormone(1-84) were similar in the t wo groups. None of these hormones was affected during the observation time after the injection of 1,25-D. In conclusion, acute administratio n of 1,25-D caused a fast and likely nongenomic-mediated decrease in c ardiac output in patients with essential hypertension, which together with a transient BP increase implies a 1,25-D-induced increase in tota l peripheral resistance. These data suggest an enhanced cardiovascular responsiveness to 1,25-D in hypertensive compared to healthy normoten sive subjects. (C) 1998 American Journal of Hypertension, Ltd.