The Nb-2 cell bioassay could be a useful tool for evaluating human growth hormone (hGH) bioactivity, but is not specific for hGH since it relies on the ability of the hormone to produce effects by cross-reacting with the lactogenic receptor on Nb-2 cells. We studied the biological activity of both endogenous and exogenous hGH in short patients using the Nb-2 bioassay after inhibiting the mitogenic effect of the other lactogenic hormone, that is human prolactin (hPRL), by adding a specific antibody against hPRL to each assay. The in vitro study showed a significant (p<0.0001) increase in Nb-2 cell proliferation when increasing concentrations of highly purified hGH were added to the cell culture. A complete inhibition of Nb-2 cell replication was observed after adding a specific antibody against hGH. The in vivo study showed a significantly (p<0.0001) lower hGH bioactivity (4.90+/-0.28 ng/ml) evaluated during stimulation tests in 9 children with total idiopathic GH deficiency, mean age 9.25+/-1.99 years, in comparison with that found in 11 short children with normal growth velocity, mean! age 8.22+/-1.41 years (12.25+/-1.19 ng/ml). Likewise, serum GH levels measured by immunofluorometric assay IFMA in the same serum samples were significantly (p<0.001) lower in the 9 GH-deficient (1.97+/-0.37 ng/ml) than in the 11 short children (21.85+/-2.71 ng/ml). Moreover, we evaluated GH concentrations using both IFMA and the Nb-2 cell bioassay in serum samples collected from another 11 idiopathic GH-deficient children, mean age 10.71+/-1.18 years, before and then, 6 and 24 hours following the 1st injection of r-hGH (0.1 IU/kg sc), Serum GH values measured by both IFMA and Nb-2 bioassay significantly (p<0.0001) increased 6 hours after r-hGH administration and decreased to reach basal levels after 24 hours. In conclusion, the Nb-2 cell bioassay with minor modifications seems to provide a specific and sensitive assessment of hGH bioactivity. (C),1998, Editrice Kurtis.
Bozzola, M., Zecca, M., Locatelli, F., Radetti, G., Pagani, S., Autelli, M., Tatò, L., Chatelain, P., Evaluation of growth hormone bioactivity using the Nb2 cell bioassay in children with growth disorders, <<JOURNAL OF ENDOCRINOLOGICAL INVESTIGATION>>, 1998; 21 (11): 765-770. [doi:10.1007/BF03348043] [https://hdl.handle.net/10807/264736]
Evaluation of growth hormone bioactivity using the Nb2 cell bioassay in children with growth disorders
Locatelli, Franco;
1998
Abstract
The Nb-2 cell bioassay could be a useful tool for evaluating human growth hormone (hGH) bioactivity, but is not specific for hGH since it relies on the ability of the hormone to produce effects by cross-reacting with the lactogenic receptor on Nb-2 cells. We studied the biological activity of both endogenous and exogenous hGH in short patients using the Nb-2 bioassay after inhibiting the mitogenic effect of the other lactogenic hormone, that is human prolactin (hPRL), by adding a specific antibody against hPRL to each assay. The in vitro study showed a significant (p<0.0001) increase in Nb-2 cell proliferation when increasing concentrations of highly purified hGH were added to the cell culture. A complete inhibition of Nb-2 cell replication was observed after adding a specific antibody against hGH. The in vivo study showed a significantly (p<0.0001) lower hGH bioactivity (4.90+/-0.28 ng/ml) evaluated during stimulation tests in 9 children with total idiopathic GH deficiency, mean age 9.25+/-1.99 years, in comparison with that found in 11 short children with normal growth velocity, mean! age 8.22+/-1.41 years (12.25+/-1.19 ng/ml). Likewise, serum GH levels measured by immunofluorometric assay IFMA in the same serum samples were significantly (p<0.001) lower in the 9 GH-deficient (1.97+/-0.37 ng/ml) than in the 11 short children (21.85+/-2.71 ng/ml). Moreover, we evaluated GH concentrations using both IFMA and the Nb-2 cell bioassay in serum samples collected from another 11 idiopathic GH-deficient children, mean age 10.71+/-1.18 years, before and then, 6 and 24 hours following the 1st injection of r-hGH (0.1 IU/kg sc), Serum GH values measured by both IFMA and Nb-2 bioassay significantly (p<0.0001) increased 6 hours after r-hGH administration and decreased to reach basal levels after 24 hours. In conclusion, the Nb-2 cell bioassay with minor modifications seems to provide a specific and sensitive assessment of hGH bioactivity. (C),1998, Editrice Kurtis.
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