N-acetylated endorphins in ovine anterior pituitary and neuro-intermediate lobe

We have used an antiserum for immunohistochemistry and RIA/RP-HPLC which recognizes all fragments of N-acetylated endorphin (NacEP). In the rat neuro-intermediate lobe (N-IL), in addition to the N-acetylated forms of immunoreactive-beta-endorphin (ir-beta EP) already reported, we have demonstrated Nac beta EP as a minor component. In the sheep pituitary processing of beta EP is markedly different. In the anterior pituitary (AP), staining was indistinguishable with beta EP and NacEP antisera, in contrast with the rat where many fewer AP cells stained with the NacEP antiserum. Secondly, as in the rat, all N-IL cells stained with both antisera; on RP-HPLC, however, the major forms of NacEP in the sheep N-IL were Nac beta EP (approximately 40%), Nac beta EP (approximately 25%) and Nac beta EP (approximately 20%), with Nac beta EP (approximately 2%) as a minor component. A similar profile was seen on RP-HPLC of sheep AP. These data suggest that (1) patterns of processing in sheep AP are similar to those in N-IL, though the extent of acetylation is less and (2) in the sheep pituitary low molecular weight acetylated fragments predominate, in contrast with the rat.