SYNTHESIS AND BIOLOGICAL-ACTIVITY OF 4-GAMMA-MELANOTROPIN PEPTIDES DERIVED FROM THE CRYPTIC REGION OF THE "ADRENOCORTICOTROPIN-BETA-LIPOTROPIN PRECURSOR

A third melanotropin coding fragment named γ-MSH was discovered by Nakanishi et al (Nature 278, 423-427 (1979)) in the cryptic region outside the portion coding for ACTH and β-LPH in the ACTH/β-LPH precursor mRNA isolated from the intermediate lobe of bovine pituitary. Four possible γ-MSH peptides derived from this coding fragment were synthesized by solid-phase methodology and their bioactivity determined in an in vitro MSH assay as well as the anterior pituitary primary culture assay. Relative to α-MSH, the melanotropic activities of Ac-γ1-MSH, γ1-MSH, γ2-MSH and γ3-MSH are 7.3 × 10-4, 3.3 × 10-5, 1.4 × 10-4 and 4.6 × 10-7 respectively. None of these γ-MSH peptides releases LH, FSH, PRL, GH and TSH in the pituitary culture medium at a dose as high as 100 ng per dish. © 1979.