STUDIES ON THE PITUITARY MELANOPHORE-EXPANDING HORMONE WITH REFERENCE TO ITS IDENTITY WITH ACTH

Abstract

SUMMARY: Three different melanophore-expanding extracts were subjected to two methods of heating in alkali and assayed, using intact Xenopus. The results for treated and untreated material were statistically analysed. 1. Heating a simple ox posterior pituitary extract (OxPLP) in alkali by either method increased its melanophore-expanding ('B') activity, but the slope of the dose-response curve did not differ significantly from that for the untreated extract. 2. The dose-response curve for an acetone precipitated extract (APP) of OxPLP differed significantly in slope from that of the OxPLP extract itself. The APP powder did not change its activity when boiled at pH 13·0 for 3 min. 3. Heating in alkali of a commercial ACTH preparation destroyed approximately 90% of its B activity. 4. The increase in activity of alkali heat-treated extracts can be reliably determined by Xenopus white adapted for long periods of time, provided they receive frequent injections of B-active material.