alpha-N-acetylated beta-endorphin is differentially processed in the normal and hypothalamo-pituitary-disconnected...

We have used specific radioimmunoassay and high-performance liquid chromatography (HPLC) to determine content and molecular forms of pituitary alpha-N-acetylated endorphin (NacEP) in the intact and hypothalamo-pituitary-disconnected (HPD) sheep. No significant differences were seen in anterior pituitary (AP) immunoreactive (ir-) NacEP levels (control = 4.34 +/- 0.45 ng/mg; HPD = 4.38 +/- 0.83 ng/mg; n = 4) or in HPLC profiles following pituitary disconnection. In contrast, levels of ir-NacEP in the HPD intermediate lobe (IL) (263 +/- 16.5 ng/mg; n = 4) were double those in the control (110 +/- 14 ng/mg; n = 4), accompanied by a marked change in the molecular profile. In the control IL, the major species were Nac alpha EP (30%), Nac gamma EP (30%) and Nac beta EP1-27 (35%); in HPD IL, Nac beta EP1-27 (65%) is the dominant molecular form, with Nac alpha EP (11%) and Nac gamma EP (9%) relatively minor components.