Concomitant changes of ACTH, β-endorphin and N-terminal portion of pro-opiomelanocortin in rats

Radioimmunoassay developed to measure N-terminal peptide of pro-opiomelanocortin isolated from porcine pituitaries was used to measure changes in the concentration of immunoreactive material in rat plasma. The N-terminal peptide immunoreactive material decreased in plasma after hypophysectomy of both female and male rats below the level of detectability and substantially increased after adrenalectomy as compared to normal control rats. The same changes were observed when β-endorphin and ACTH like immunoreactive material was measured. The primary culture of rat anterior pituitary cells released ACTH and N-terminal peptide-like immunoreactive material into the incubation medium. The results seem to indicate that the N-terminal immunoreactive material is a secretory product produced by the pituitary gland.