Re-appraisal of the Evidence for the Metabolic Conversion of Vasopressin into a Less Active Derivative

Abstract

THE intermediary metabolism of peptide hormones is unknown, and it is therefore of great interest that Dicker and Greenbaum¹ have recently suggested “that both kidney and liver slices transform vasopressin into substances of lower antidiuretic activity”. They reached this conclusion because they found that the activity of ‘Pitressin’, when incubated with rat kidney slices, decreased until 20 per cent of the initial antidiuretic potency remained; thereafter, there was no further inactivation. When the resultant supernatant from such an incubation mixture was added to fresh kidney slices its activity remained constant although it could be completely abolished by liver slices. Thus, the property by which Dicker and Greenbaum distinguish between vasopressin and the product of its metabolism is that the latter resists inactivation by kidney slices while vasopressin does not.