THE ACUTE AND PROLONGED EFFECT OF PORCINE CALCITONIN ON URINE ELECTROLYTE EXCRETION IN INTACT AND PARATHYROIDECTOMIZED RATS

Abstract

ABSTRACT The effect of calcitonin on the urinary excretion of calcium, magnesium, phosphorus, sodium, potassium, and creatinine was studied in intact and parathyroidectomized (PTX) rats. A single injection of porcine calcitonin was followed by a reduced excretion of calcium and magnesium and an increased excretion of potassium. A phosphaturic effect was observed only in the intact rats. The urinary changes did not depend upon impurities in the preparation used, since similar results were obtained with synthetic porcine calcitonin. The urinary electrolyte excretion was also followed in rats given injections of porcine calcitonin every 3 hours, for 3 days. A marked calciuric effect of the hormone was seen in the intact rats, after a transitory decrease in the excretion of calcium at the start of the treatment. The hypercalciuria could hardly be explained by an increased parathyroid action, but rather by a direct effect of calcitonin on renal tubular function. The excretion of magnesium closely followed that of calcium in both intact and PTX rats. A marked phosphaturic and natriuretic effect of calcitonin was observed during prolonged treatment with the hormone. The changes in serum calcium were followed in intact rats treated in a similar way with repeated injections of calcitonin. A hypercalcaemic peak was seen, when the treatment was interrupted, indicating an increased parathyroid action.