Abstract
No assays have been reported so far for quantitative immunologic measurements of GHBP-retatcd peptides in human serum. For this purpose polyclonal antisera were raised in rabbits against partial sequences of the extracellular domain of the human GH receptor, which were selected on the basis of secondary structure calculations suggesting their location on the surface of the molecule together with high flexibility. One of the peptides was finally chosen for establishing a RIA using this pentadecapeptide for radiolabelling and for preparation of standards. The specificity of Hie antiserum was examined by FPLC size exclusion chromatography (SEC) and Western blotting (WB). In SEC, GHBP RIA activity coeluled with the GH-binding activity at 55 kDa with a minor peak at 106 kDa. By WB, 2 bands at 54 and 73 kDa were visible. High concentrations of GH did not interfere in the GHBP RIA. Results of GHBP measurements were referred to the peptide standard and are given as ng/ml peptide equivalents.
Results: Short children with low IGF-I levels (<5th percentile, n=13, age 11.0±2.3 yr) had significantly decreased GHBP levels as compared to short children with normal IGF-I levels (n=13, 12.2±2.3 yr) or an age-matched control group (n=26, 11.6±3.6 yr): (mean±SD) 31±15 ng/ml versus 48±13 ng/ml or 46±23 ng/ml resp. (p<0.05). Patients with chronic renal failure (CRF) with residual glomerular filtration (n=10, age 11.1±3.8 yr) had markedly diminished GHBP levels (11±4 ng/ml. p<0.001), whereas patients with end-stage renal failure (ESRF; n=10, 13.0±2.9 yr) showed a remarkable interindividual variation (37±35 ng/ml, range 4 - 101 ng/ml).
Conclusions: 1) The results of RIA measurements compare qualitatively well with functional assays. 2) Low IGF-I levels in short children may be related to low GHBP (or GH receptor) levels. 3) Low GHBP levels in uremic patients may be due to impaired synthesis. 4) In extreme cases of ESRF diminished GHBP synthesis may be counterbalanced by impaired clearance leading to elevated GHBP levels.
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Krutsch, J., Blum, W., Selisko, T. et al. RADIOIMMUNOLOGIC DETERMINATION OF GHBP IN SERA OF CHILDREN WITH SHORT STATURE. Pediatr Res 33 (Suppl 5), S48 (1993). https://doi.org/10.1203/00006450-199305001-00271
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DOI: https://doi.org/10.1203/00006450-199305001-00271