A PERMANENT PREPARATION ALLOWING MEASUREMENTS OF SECRETION OF PARATHYROID HORMONE IN CONSCIOUS GOATS

Abstract

A preparation for estimations of rates of secretion of parathyroid hormone (PTH) in conscious goats is described. The procedure involved surgical isolation of a thyroid with its indwelling parathyroid gland, leaving the blood supply intact. Permanent access to the arterial and venous supplies of the preparation was secured by exteriorization of the jugular vein and carotid artery in skin-covered loops. The remaining parathyroids were removed leaving the isolated parathyroid gland as the only source of the hormone. For the seven goats operated on, the preparation has worked satisfactorily from the start in five and also in the remaining two after a reoperation to cut an accessory venous drainage. The loops have been catheterized repeatedly for extended periods of time and the preparation has proved useful for periods of up to 3 years. Secretion of PTH was measured in one goat at two consecutive parturitions. In late pregnancy, secretion rates of 0·7–0·9 ng/kg per min were observed when the dietary calcium intake was adequate. In the first weeks of lactation, secretion increased to 1·2–1·5 ng/kg per min when the intake of calcium was adequate and to 2·0–2·2 ng/kg per min when calcium intake was inadequate. Reductions in calcium intake led to increased rates of secretion of PTH both during pregnancy and during lactation. The results indicate that the preparation may be useful in the study of changes in PTH secretion both acutely and in connection with long-term studies of dietary adaptations of the calcium metabolism.