Pituitary immunoreactive γ-melanotropins are glycosylated oligopeptides

Abstract

Nakanishi et al.¹ have recently characterised the complete sequence of the mRNA isolated from the intermediate lobe of bovine pituitary which codes for the 31,000 molecular weight (31 K) precursor protein of corticotropin/β-lipotropin (ACTH/β-LPH). The corresponding amino acid sequence translated from this mRNA revealed in the cryptic region of the precursor protein a fragment sharing a common amino acid sequence with the α- β-melanotropins (α-MSH, β-MSH) and thus named γ-MSH¹. To study whether this γ-MSH fragment is also processed and released as a biologically active substance and to ascertain its location in the pituitary and possibly in the brain, we have raised antibodies to the synthetic replicate of γ₃-MSH (ref. 2). We report here the detection of at least two γ-MSH-like peptides in the pituitary using these antibodies in a radioimmunoassay (RIA) and, furthermore, evidence that these two peptides are glycosylated.