Distribution of adrenocorticotrophic and lipotrophic peptides in the rat

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), alpha-melanocyte-stimulating hormone (alpha-MSH), and alpha- and beta-endorphin. A large molecular weight, glycosylated form of corticotrophin-like intermediate lobe peptide (CLIP) which we have termed big CLIP, and a beta-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 gamma-lipotrophic hormone (gamma-LPH) was detected. In the pars distalis, the larger peptides 1-39 ACTH and beta-LPH predominated, whereas in the pars intermedia, the smaller peptides alpha-MSH, CLIP, beta- and alpha-endorphin were more abundant. Chromatography of rat plasma revealed peaks of immunoreactivity in the corresponding positions to those detected in the pituitary gland.