Decrease of calcium turnover during the onset of mineralocorticoid hypertension in the rat

Abstract

Calcium turnover was studied during the early phase and during the sustained phase of arterial hypertension elicited in the rat by desoxycorticosterone (DOCA) and NaCl. Parameters representative of short term and long term phenomena involved in calcium metabolism were derived from the analysis of the initial segment of the curve describing the decrease with time of serum specific activity after intravenous injection of 45Ca. Two weeks after the onset of the mineralcorticoid treatment, blood pressure was higher, total serum calcium and all parameters of calcium turnover lower in the NaCl-DOCA treated rats than in the controls. Both arterial hypertention and the perturbations of calcium metabolism did not take place under the influence of DOCA alone. Ten weeks after the onset of the mineralocorticoid treatment, total serum calcium and calcium turnover were no longer different in hypertensive and in control rats. It is concluded that the marked but transient perturbations of calcium metabolism that were put into evidence in the present study were induced by the DOCA-elicited modifications of sodium metabolism taking place during the onset of hypertension. We propose the hypothesis that decreased calcium turnover in soft tissues may partially protect the rats against the development of increased vascular resistence. In addition the results raise the question of the reason why calcium turnover rates and serum calcium were reduced under the influence of DOCA and NaCl in rats with intact parathyroid and thyroid glands.