The preferential release of beta-endorphin from the anterior pituitary lobe by Corticotropin Releasing Factor (CRF)

THE post-translational processing of proopiomelanocortin (POMC) to Beta-endorphin (/3-End) and Beta-lipotropin (flLPH) differs in the anterior and intermediate lobes of rat pituitary. In the anterior lobe (AL), the molar ratio of/3-End to fl-LPH is approximately 1:2, while in the intermediate lobe (IL), virtually all of the precursor is processed to/3-End sized or smaller material [2, 5, 12]. One might expect, therefore, that the products released during stimulation of each lobe would reflect these molar ratios; the anterior lobe should release primarily/3-LPH, while the IL would release /3-End 1-31 or modified forms of fl-End (e.g., alpha N-acetylated fl-End 1-27). Consequently, the circulating levels in plasma should reflect both anterior and intermediate lobe contributions.