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Radioimmunoassay of somatomedin‐C in the baboon ( Papio cynocephalus ): A comparison of multiple techniques of measurement
Author(s) -
Copeland K. C.,
Johnson D. M.,
Underwood L. E.,
Van Wyk J. J.
Publication year - 1983
Publication title -
american journal of primatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.988
H-Index - 81
eISSN - 1098-2345
pISSN - 0275-2565
DOI - 10.1002/ajp.1350050206
Subject(s) - baboon , radioimmunoassay , sephadex , chromatography , chemistry , endocrinology , somatomedin , medicine , biology , hormone , biochemistry , enzyme , growth hormone
This study was undertaken to assess the nature of somatomedin‐C (SM‐C) in baboon ( Papio cynocephalus ) blood and to compare various methods for estimating SM‐C concentrations. Parallel dose‐response curves were obtained with normal baboon serum, normal human serum, and purified SM‐C. Recovery of purified SM‐C added to baboon serum over a wide dosage range (n = 17) was 111 ± 12%, with slightly better recovery at higher potencies. Chromatography of normal baboon serum on Sephadex G‐200 at neutral pH produced a profile similar to that observed in the human, as did samples chromatographed on Sephadex G‐50 in acid. Although the SM‐C content in acid chromatographed plasma was approximately 2.5 times higher than in native unprocessed plasma, there was excellent correlation between the values (r = 0.9143, p < 0.0001). The SM‐C in baboon plasma which had been preincubated with glycine HCl was approximately twice that of unprocessed plasma, but the correlation between the two methods was excellent (r = 0.9593, p < 0.0001). The correlation between values obtained after simple acid‐ethanol extraction and those observed in unextracted plasma were also significant (r = 0.7689, p < 0.0001). Following a series of four injections of human growth hormone (hGH) to a normal baboon, plasma SM‐C rose approximately sevenfold above the initial concentration and returned to basal levels five days after the final injection. These studies show that although the radioimmunoassay (RIA) for SM‐C in unprocessed baboon plasma does not measure all of the SM‐C present, it provides a reliable index of the total SM‐C concentration and reflects GH status in the baboon.