Developmental changes in the processing of ACTH in the anterior pituitary of the amphibian,Ambystoma tigrinum

Abstract

Acid extracts of anterior pituitaries obtained from larval, neotene, postmetamorphic young adult, and sexually active adult Ambystoma tigrinum were fractionated by gel filtration and analyzed by RIA. In larval, neotene, and postmetamorphic adults the molar ratio of ACTH(1-39) to alpha-MSH was, respectively, 1.3:1, 1:1.3, and 1:1.3. However, in sexually mature adults the molar ratio of ACTH(1-39) to alpha-MSH was 8:1. These results indicate that prior to and immediately after metamorphosis, both ACTH(1-39) and alpha-MSH are major end products of corticotropic cells in this species. As postmetamorphic animals reach sexual maturity, there is a shift in the processing of ACTH which yields ACTH(1-39) as the major end product of corticotropic cells. In the corticotropic cells of adults only trace amounts of alpha-MSH are produced.