Lactogenic hormone responsive element reporter gene activation assay for human growth hormone

We investigated the bioactivity of GH and compared with their immunoactivity in GH bioassay system using lactogenic hormone responsive element (LHRE) reporter gene in Chinese hamster ovary cells transiently co-transfected with human GH receptor cDNA and LHRE/TK-luciferase reporter gene (LHRE/Luc). The recombinant and serum GH but not prolactin almost equally were able to induce LHRE/Luc in a significant and dose-dependent manner, which were equally suppressed by anti-GH. Recombinant GH binding protein (GHBP) at 100 ng/ml but not at 20 ng/ml slightly attenuated GH-induced LHRE/Luc. The serum GH bioactivity (ng/ml) in patients with acromegaly were equal near to their immunoactivity, whereas the bioactivity of the serum GH in a short child with mutant GH (R77C) revealed lower than their immunoactivity. The bioactivity of the recombinant mutant GH was as half as that of wild type GH, thus confirming an antagonistic property of mutant GH. LHRE reporter gene activation assay is useful to measure the GH bioactivity in addition to the conventional bioassay using cell proliferation.