EFFECTS OF PORCINE CALCITONIN ON SOME URINE ELECTROLYTES IN THE RAT

Abstract

ABSTRACT Bidaily (b. i. d.) subcutaneous administration of porcine calcitonin (CT) to intact rats resulted in dose-related increases in urinary excretion of water, calcium, phosphorus and magnesium. The effects required several days of treatment to reach maximum levels and persisted for several days after treatment ceased. Although hypocalcaemia occurred immediately following CT injections in chronically treated rats, animals treated for 8 days were significantly hypercalcaemic 18 hours later. Bidaily administration of CT (9 a. m. and 3 p. m.) induced a distinct 24 hour periodicity in urinary excretion patterns of calcium, magnesium and urine volume, with maximal excretion at night. In the case of magnesium, this represented a direct reversal of the diurnal excretion pattern seen in control rats. Urine volume and urine calcium were increased in parathyroidectomized (PTX) and thyroparathyroidectomized (TPTX) rats treated daily with CT. Surprisingly, the initial low blood calcium levels of these rats were elevated toward normal with daily CT treatment and returned to pretreatment levels following cessation of CT injections. PTX rats treated with parathyroid extract (PTE) exhibited hypercalcaemia and hypercalciuria. Hypercalcaemia was only partially prevented by simultaneous treatment with high doses of CT and hypercalciuria was essentially unaltered.