DISTRIBUTION OF ADRENOCORTICOTROPHIC AND LIPOTROPHIC PEPTIDES IN THE RAT

Abstract

Intermediate and anterior lobes from the pituitary glands of female Wistar rats were freshly dissected and chromatographed on Sephedex G-50 and BioGel P6. Fractions were monitored with radioimmunoassays for NH2- and CO2H-terminal adrenocorticotrophin (ACTH), α-melanocyte-stimulating hormone (α-MSH), and α- and β-endorphin. A large molecular weight, glycosylated form of corticotrophin-like intermediate lobe peptide (CLIP) which we have termed big CLIP, and a β-MSH-like molecule were identified in the pars intermedia and in both lobes, a major peak of activity with the elution characteristics and cross-reactivity of γ-lipotrophic hormone (γ-LPH) was detected. In the pars distalis, the larger peptides 1–39 ACTH and β-LPH predominated, whereas in the pars intermedia, the smaller peptides α-MSH, CLIP, β- and α-endorphin were more abundant. Chromatography of rat plasma revealed peaks of immunoreactivity in the corresponding positions to those detected in the pituitary gland.