Some of the [alpha]-NH2-acetylated [beta]-endoprhin-like material in rat and monkey pituitary and brain is acetylated [alpha]- and [beta]-endorphin

Abstract

There are several studies demonstrating the existence of [alpha]-NH2-acetylated (N-Ac) forms of [beta]-endorphin in the intermediate lobe of several species (1,4,6). These include N-Ac-[beta]-endorphin(1-31), N-Ac-[beta]-endorphin(1-27) and N-Ac-[beta]-endorphin(1-26). The existence of N-acetylation of brain [beta]-endorphin is more controversial (5,6). Using molecular sieving, HPLC, and several radioimmunoassays, either directed at the midportion of [beta]-endorphin or at only N-acetylated opioids, we have studied brain multiple forms (cf. Akil, 1982). We have noted that little or no acetylation of [beta]-endorphin-sized material occurs in hypothalamus, and a small amount of N-acetylation appears to take place in the midbrain and the medulla. These results will be described in detail elsewhere (Akil et al., in preparation), but point the fact that processing of [beta]-endorphin(1-31) in brain is different than either lobe, with the production of [beta]-endorphin(1-27) and [beta]-endorphin(1-26) being more predominant in brain terminal areas than in the neuro-intermediate lobe. In the course of these experiments we noted the existence of a smaller-sized material which reacted with our N-acetyl-[beta]-endorphin antibody. The following study describes the partial characterization of this material as N-Ac-[alpha]- and N-Ac-[beta]-endorphin (i.e., the N-acetylated forms of [beta]-endorphin (1-17) and [beta]-endorphin(1-16).