Multiplication-stimulating activity (MSA) in the medium of cultured rat liver cells was purified 120-fold by chromatography on Dowex 50W and Sephadex G 50. MSA was labelled with 125I-iodine and bound to a human placental membrane receptor. An assay for somatomedin-like receptor activity (SmLRA) in unextracted serum was based on the displacement of 125I-MSA from the placental receptor. The mean lambda (precision) was 0.063, sensitivity was less than 0.006 SmLRA units and interassay variation was 18%. The mean (+/- S.D.) SmLRA concentrations in 13 normal subjects, 7 growth hormone deficient patients and 8 patients with active acromegaly were 0.86 +/- 0.19, 0.34 +/- 0.08 and 2.34 +/- 0.82 U/ml, respectively. This assay may have potential clinical application in disorders of growth hormone secretion.
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BRINSMEAD et al. (1978) studied this question.