Effect of Acute and Chronic Calcium Administration on Plasma Renin

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To evaluate the effect of Ca++ on renin release, plasma renin activity (PRA) was measured after acute and chronic Ca++ administration. 1% CaCl2 was infused into one renal artery of 10 anesthetized dogs (0.3 mg/kg/min). The excreted fraction of filtered calcium (EFca++) and EFNa+ from the infused kidney were elevated (P < 0.04) during three successive 15-min infusion periods. Serum calcium concentration was significantly elevated (P < 0.001). Creatinine clearance, systemic arterial pressure, and renal blood flow did not change (P > 0.10). Compared to control (45 ng/ml/h±5.2 SE), renal venous PRA was suppressed (P < 0.0001) after infusion of Ca++ for 15, 30, and 45 min (20 ng/ml/h±4.6, 16 ng/ml/h±4.0, and 13 ng/ml/h±2.7, respectively). 15 and 30-min after infusion, PRA did not differ from control (P > 0.20). Chronic Ca++ loading was achieved in Sprague-Dawley rats by replacing drinking water with 1% CaCl2 for 17 days. At sacrifice, serum Ca++, Na+, and K+ of controls (n = 12) did not differ (P > 0.60) from Ca++-loaded rats (n = 12). Ca++ excretion (467 μeq/24 h±51) was elevated (P < 0.001) compared to controls (85 μeq/24 h±12). PRA (8.6 ng/ml/h±1.4) and renal renin content of Ca++-loaded rats did not differ from controls (P > 0.80). However, after 8 days of sodium deprivation, both PRA and renal renin content of calcium-loaded animals were significantly lower than the respective values in pair-fed controls (P < 0.005). During the period of sodium deprivation, calcium-drinking animals were in greater negative sodium balance than controls (P < 0.005). The data are consistent with the hypothesis that acute and chronic calcium administration inhibit renin secretion.

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