INACTIVATION AND DEGRADATION OF PORCINE CALCITONIN BY RAT LIVER, AND RELATIVE STABILITY OF SALMON CALCITONIN

Abstract

SUMMARY Slices and homogenates of a number of rat tissues inactivated porcine calcitonin labelled with 125I; the most active tissue was the liver. Maximal activity was found in rat liver supernatant. The reaction was pH- and dose-dependent, the active principle was non-diffusible, inhibited by p-chloromercuribenzoate and EDTA, and destroyed by heat. Biological activity of calcitonin was lost parallel with the breakdown of the labelled calcitonin (as measured by loss of trichloroacetic acid precipitability). Salmon ultimobranchial calcitonin was much less susceptible to inactivation by rat liver supernatant than the porcine hormone, which may explain the high potency and prolonged action of the salmon hormone in the rat.