CORTICOTROPIN /β-LIPOTROPIN BIOSYNTHESIS, PROCESSING, AND RELEASE IN NELSON'S SYNDROME

Abstract

Biosynthesis and processing of ACTH/β-lipotropin was studied in Nelson's syndrome pituitary tumor tissue grown in tnonolayer culture. Radiolabeled peptides were immunoprecipitated and fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS/PAGE). Important findings include: 1) a virtual absence of 13K ACTH or 3.5K B-endorphin production; 2) evidence indicating the presence of a 24–26K ACTH and β-LPH containing intermediate (which implies a different order of processing from that reported in the mouse); 3) An extremely rapid rate of turnover and release of ACTH and β-lipotropin (β-LPH) similar to that of the mouse AtT20/D16v pituitary tumors. The latter finding is consistent with an intrinsic pituitary cell defect in the pathogenesis of this disorder.