Alteration of the Duration of Action of Parathyroid Hormone after Partial Purification

Abstract

THE earliest methods of assaying parathyroid hormone depended on its ability to cause a rise in the concentration of plasma calcium in normal dogs 16–18 hr. after injection¹. Recently, Davies et al. ² have described a method of assaying this calcium-mobilizing factor, utilizing the parathyroidectomized rat as the test animal. Following the subcutaneous injection of crude parathyroid extracts (or ‘Parathormone’, Eli Lilly) into such animals the concentration of plasma calcium begins to increase in 2–3 hr., reaches a peak in 14–18 hr. and remains elevated for a total of 32–40 hr. (Fig. 1). On the basis of these facts, Davies et al. suggested that an adequate assay could be achieved by measuring the calcium concentration immediately before, and 18 hr. after, the injection of the test material; and comparing the change with that occurring in a similar group of animals given a standard preparation.