In vitro secretion of pro-opiomelanocortin (POMC) derived peptides in human ACTH-producing pituitary adenomas: evaluation of hormone ratios in different functional states.

In 14 cases of ACTH-producing pituitary adenomas (8 cases of Cushing's disease and 6 cases of Nelson's syndrome) dispersed cells prepared from adenoma tissue were incubated in a superfusion or static incubation system and investigated for ACTH, beta-endorphin (beta-EP) and beta-lipoprotein (beta-LPH) production. Effects of cortisol and lysine vasopressin (LVP) were evaluated. During the superfusion a qualitatively parallel secretory pattern is obtained for all hormones. Quantitatively, however, the response to LVP stimulation is more pronounced for beta-endorphin-like immunoreactivity (beta-LPH/beta-EP-IR) causing ACTH/beta-LPH/beta-EP-IR ratios to change throughout single experiments. beta-EP/beta-LPH ratios, however, which were estimated by means of Sephadex G-50 gel chromatography at various key points of the superfusion, were constant for each tumor, although variable between different adenomas, ranging from 0.68 to 2.0. The results suggest neither a differential control for the secretion of the peptides investigated within individual tumors nor a direct effect of cortisol or LVP on pro-opiomelanocortin processing. Summarizing clinical data and in vitro findings such as secretory behavior or hormone ratios, we can find no characteristic differences between Nelson's syndrome and Cushing's disease.