Inactivationin Vitroof Parathyroid Hormone Activity by Kidney Slices

Parathyroid extract was incubated aerobically with slices of rat kidney, liver, spleen and skeletal muscle and with rat plasma in phosphate buffer, pH 7.4, at 37 C for 1 hr and the supernatant was assayed for calcium-mobilizing activity according to Munson. Slices of the kidney almost completely inactivated the extract, while other tissues were relatively ineffective. Moderate inactivation was also demonstrated upon incubation with plasma. Boiling for 15 min reduced the inactivating capacity of kidney slices. Inactivation seemed to be most effective at pH 7.4. The degree of inactivation seemed to be approximately proportional to the number of slices and the length of the incubation time. (Endocrinology76: 255, 1965)