A novel specific bioassay for serum human growth hormone.
Human GH receptor (hGHR) was recently expressed on a Ba/F3 cell line, which is a mouse pro-B cell lymphoma that has been induced to become a cloned cell line (Ba/F3-hGHR). Using a Ba/F3-hGHR cell line, we have established a bioassay for serum hGH. hGH stimulated cell proliferation in a dose-dependent manner in concentrations ranging from 1 ng to 100 ng/mL. Cell proliferation was not influenced by other hormones or growth factors in the bioassay, with the exception of insulin-like growth factor I (IGF-I) and GH binding protein. Free IGF-I significantly stimulated the proliferation of Ba/F3-hGHR cells at concentrations over 25.85 ng/mL in this bioassay system, but serum IGF-I did not stimulate cell proliferation because the sensitivity of cell proliferation was insufficient for free IGF-I in serum. GH binding protein, however, did suppress cell proliferation at the highest concentration (100 ng/mL), but did not at the average concentration (20 ng/mL). Human serum stimulated cell proliferation, which was completely suppressed by anti-GH antibody. The GH bioactivity of serum samples from normal children and patients with non-GH deficient short stature correlated strongly with the serum hGH concentration determined by immunoradiometric assay (IRMA) (r = 0.967, r = 0.924, P < 0.0001, respectively). The ratio of bioactivity/IRMA was 1.01+/-0.26 in sera from normal children and 1.18+/-0.24 and 1.00+/-0.29 at basal values and peak values in GH stimulation tests, respectively, in sera from patients with non-GH deficient short stature. The bioactivity/IRMA ratio for the serum GH bioactivity of a patient who had biologically inactive GH caused by an amino acid substitution was 0.333+/-0.056 (mean +/- SD). In conclusion, we established a new sensitive bioassay for hGH that is specific for hGH somatogenic action and is useful for screening of patients with short stature caused by biologically inactive hGH.
Ishikawa
M
M
Department of Endocrinology and Metabolism, National Children's Medical Research Center, Tokyo, Japan.
Nimura
A
A
Horikawa
R
R
Katsumata
N
N
Arisaka
O
O
Wada
M
M
Honjo
M
M
Tanaka
T
T
D000906:Antibodies / Q000494:pharmacology; D001681:Biological Assay / Q000379:methods; D002455:Cell Division / Q000187:drug effects; D002648:Child; D002999:Clone Cells; D006130:Growth Disorders / Q000097:blood; D019382:Human Growth Hormone / Q000097:blood* / Q000276:immunology / Q000494:pharmacology; D006801:Humans; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014407:Tumor Cells, Cultured
D000906:Antibodies; D019382:Human Growth Hormone