Development and validation of a radioimmunoassay for peptides related to beta-melanocyte-stimulating hormone in human plasma: the lipotropins.
A radioimmunoassay is described for the measurement of human "beta-melanocyte-stimulating hormone" ("betah-MSH"). Two antisera have been used, one of which cross-reacts with synthetic betah-MSH as well as with the two larger pituitary peptides betah- and gammah-lipotropin (betah- and gammah-LPH) and the other mainly with betah-MSH and gammah-LPH. The sensitivity and reliability of the assay have been improved by employing a simple plasma extraction procedure, and the shelf-life of the iodinated betah-MSH tracer has been increased more than five-fold by storage in a concentrated human serum albumin solution. Using a 5 ml plasma sample the detection limit is 6 pg/ml. The mean resting "betah-MSH" level in normal subjects is 21 pg/ml (range 13-38 pg/ml) at 9 AM and 12 pg/ml (range 6-20 pg/ml) at 9 PM. Levels are considerably elevated (51-12,000 pg/ml) in patients with Addison's disease. Nelson's syndrome, Cushing's disease and the "ectopic" ACTH syndrome. After administration of insulin or pyrogen, the concentration of plasma "betah-MSH" increases in parallel with that of ACTH and they are approximately equivalent on a molar basis. The stability of purified betah- and gammah-LPH and endogenous "betah-MSH" when incubated in vitro in fresh blood or plasma are similar, in contrast to the less stable peptide synthetic betah-MSH. It is suggested that "betah-MSH" immunoreactivity in human plasma is due to betah- and gammah-LPH rather than betah-MSH.
D000224:Addison Disease / Q000097:blood; D000324:Adrenocorticotropic Hormone / Q000097:blood; D003429:Cross Reactions; D003480:Cushing Syndrome / Q000097:blood; D006729:Hormones, Ectopic; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007713:Klinefelter Syndrome / Q000097:blood; D008082:Lipotropic Agents / Q000097:blood*; D009074:Melanocyte-Stimulating Hormones / Q000097:blood* / Q000276:immunology; D010455:Peptides / Q000097:blood; D011749:Pyrogens / Q000494:pharmacology; D011863:Radioimmunoassay; D012711:Serum Albumin, Radio-Iodinated
D006729:Hormones, Ectopic; D007328:Insulin; D008082:Lipotropic Agents; D010455:Peptides; D011749:Pyrogens; D012711:Serum Albumin, Radio-Iodinated; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones