Effects of chronic hypocalcaemia on plasma renin activity in man.

Abstract

Abstract. A study was carried out to investigate the role of serum calcium in the regulation of renin secretion. The subjects for this study comprised of two groups. Group 1 consisted of 10 patients with primary or secondary hypoparathyroidism. Blood samples for basal PRA (plasma renin activity) were drawn at 8 a.m. when the patients were recumbent and on a normal sodium intake. Then all the patients were given a constant diet containing 10 mEq sodium for 4 days and were given 80 mg of Furosemid orally every day. On the morning of the fifth day blood samples were drawn after the patients had been upright for 4 h. These patients were treated with vitamin D2 and when normocalcaemic states were achieved the same study was repeated. Group 2 (control group) consisted of 10 normal, healthy subjects of both sexes. They were prepared for the experiment in the same way as for group 1. In the hypocalcaemic state mean serum calcium level was 5.6 ± 0.3 mg/100 ml. After treatment with vitamin D2, the mean serum calcium level was increased to 9.6 ± 0.1 mg/100 ml (P < 0.001). There was no significant difference in the mean serum sodium and potassium levels in either hypocalcaemia or normocalcaemia. But the mean stimulated PRA (12.12 ± 1.13 ng/ml/h) was found to be decreased in hypocalcaemia compared to in normocalcaemia and in the control group (22.87 ± 1.18 and 23.83 ± 0.86 ng/ml/h, respectively). The difference of means was significant (P < 0.001). There were no significant differences between basal PRA in hypocalcaemic and normocalcaemic state as well as in the control group. (P> 0.5, P > 0.2 and P> 0.5, respectively). Our results indicate that serum calcium plays an important role in the regulation of renin secretion.