Size heterogeneity of beta-MSH in ectopic ACTH-producing tumors: presence of beta-LPH-like peptide.
Gel chromatographic, immunologic and biologic properties of beta-melanocyte-stimulating hormone (beta-MSH) in tumor tissues obtained from eight patients with the ectopic ACTH syndrome were studied and compared to those of pituitary beta-MSH. Size heterogeneity of immunoreactive beta-MSH was found in all the tumors studied as well as in normal human pituitaries. Both the tumors and pituitaries contained immunoreactive beta-MSH of a larger molecular size than the well-characterized beta-MSH of small molecular size. The large molecular weight beta-MSH also predominated in the plasma. It was found to be bioactive by an in vitro MSH assay, immunologically indistinguishable from human beta-MSH, and chromatographically very similar to beta-lipotropic hormone (beta-LPH). Tryptic  digestion of the large molecular weight beta-MSH under controlled conditions promptly produced bioactive beta-MSH of small molecular size, followed by the appearance of immunologically active but biologically inert fragments. These results suggest that the ectopic ACTH-producing tumor as well as the pituitary elaborate beta-LPH-like peptide which might be the predominant component of immunoreactive beta-MSH in man.
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000276:immunology / Q000378:metabolism*; D008875:Middle Aged; D008970:Molecular Weight; D009362:Neoplasm Metastasis; D009384:Paraneoplastic Endocrine Syndromes / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism; D014357:Trypsin
D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D014357:Trypsin