Growth hormone specific stimulation of mitosis by size-fractionated serum from patients with growth hormone insufficiency: a study on the rat lymphoma cell line, Nb2.
The aim was to investigate the bioactivity of a high-molecular weight human growth hormone, identified following molecular sieve chromatography of serum. Nine patients with pituitary disease and GH insufficiency were studied. All patients had non-detectable levels of immunoreactive GH, less than 0.2 micrograms/l, in diurnal serum profiles. GH bioactivity was determined before and after size-fractionation of serum. The bioassay is based on the finding that a rat lymphoma cell line, Nb2, proliferates in the presence of lactogens. GH and PRL immunoreactivities were measured by radioimmunoassays. Pronounced GH immunoreactivity was found in fractions of sera from 7 out of the 9 patients and of 2 of 4 control sera, particularly in fractions corresponding to the elution volume of high-molecular weight proteins (greater than 160 kD). PRL immunoreactivity was only detected in fractions corresponding to the elution volume of monomeric PRL. Unfractionated serum had a dose-dependent mitogenic effect on the Nb2 cells. GH-antibodies could not inhibit this effect. Fractions of serum obtained from the patients stimulated Nb2 cell division as well. The mitogenic effect of serum fractions could be inhibited by GH-antibodies. Thus, high-molecular weight GH circulating in patients with GH insufficiency were shown to exert a GH-specific bioactivity in vitro after size-fractionation.
Luthman
M
M
Department of Endocrinology, Karolinska Hospital, Stockholm, Sweden.
Wallerman
E
E
Roos
P
P
Werner
S
S
D000818:Animals; D001681:Biological Assay; D002850:Chromatography, Gel; D013006:Growth Hormone / Q000097:blood / Q000172:deficiency* / Q000494:pharmacology; D006801:Humans; D008214:Lymphocytes / Q000473:pathology; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology; D008938:Mitosis / Q000187:drug effects; D008970:Molecular Weight; D011863:Radioimmunoassay; D051381:Rats; D014407:Tumor Cells, Cultured
D013006:Growth Hormone