Effect of acute and chronic vitamin D administration on systemic renin angiotensin system in essential hypertensives and controls

Aim: To investigate the systemic renin-an-giotensin system (RAS) in essential hypertensives (EH) and controls (C) after short- and long-term vitamin D receptor activation. Design: Ten consecutive EH (under controlled low-salt diet) and 10 C underwent calcitriol administration (0.25 µg bid) for 1 week (Group A). Eighteen consecutive EH under angiotensin II receptor antagonist therapy received a single oral dose of 300,000 IU of cholecalciferol and were followed up for 8 weeks (Group B). Methods: In basal conditions and at the end of the study (1 week in Group A and 8 weeks in Group B), plasma renin activity (PRA), plasma active renin, aldosterone, and angiotensin II were evaluated, as well as blood pressure, plasma 25-hy-droxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)2D], and PTH. Results: In Group A, plasma 25(OH)D levels in EH and C were below the normal range, although lower levels were found in the former. No association between basal plasma 25(OH)D or 1,25(OH)2D levels and blood pressure values or RAS components was observed either in the whole group or in the two subgroups. Calcitriol administration did not affect any RAS parameter either in EH or in C. In Group B, cholecalciferol significantly increased 25(OH)D and 1,25(OH)2D levels without interfering with the angiotensin II receptor antagonist-induced increase in RAS components. No correlation was found between plasma 25(OH)D or 1,25(OH)2D levels and blood pressure values or RAS parameters before and after cholecalciferol administration. Conclusions: The present data suggest that, in our experimental conditions, vitamin D receptor activation is unable to influence systemic RAS activity.