Human parathyroid hormone extracted from adenomata was assayed biologically by the release of calcium from mouse calvaria in organ culture and immunologically by immunoassay. The human hormone gave a logdose response curve for calcium release and assayed at 12 units/mg in terms of the M.R.C. Bovine Research Standard A. Reduction with hot cysteine hydrochloride increased the biological activity of human hormone threefold, and the bovine hormone 4.5 fold. An increase in immunological activity could only be shown with bovine hormone, and the purer the preparation the less was the activation of both biological and immunological potencies. Oxidation with hydrogen peroxide destroyed the biological activity of the bovine hormone but some residual immunological activity of the bovine and human hormones could always be detected. Back reduction with hot cysteine hydrochloride restored the biological and immunological activities of the bovine hormone and the immunological activity of the human hormone but never to the levels of the untreated hormones. It is suggested that these changes in potency can be induced by changes in the chemistry of the molecule rather than in its metabolism and that the immunological differences between bovine and human hormone represent minor differences in the amino acid sequence of these two hormones.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism