The binding of different biosynthetic and extracted human growth hormones to the growth hormone-binding protein of human serum: a comparative study.

This study of the human growth hormone binding protein (GHBP) was undertaken using several samples of hGH, extractive or recombinant, from different origins. They were labelled in identical conditions and assayed by gel chromatography after incubation with three human sera having different levels of binding activity. For each serum the binding activities of the five recombinant hormones were very close and significantly higher (P less than 0.005) then the binding activities of the 2 extractive hormones. A radioactive peak which appeared in the zone of high molecular weights was more important with extractive than with recombinant hormones (P less than 0.01). This peak increased with the ageing of the tracer and appeared even when the tracer was incubated in the absence of serum. Thus, it is for its main part not related to another binding protein but, more likely, to a polymerization of the hormone. These data point out the importance of accurate technical conditions to have a reproducible assay for GHBP and to interpret the results in studies of growth disturbances.