Abstract
We have applied the Eluted Stain Assay (ESTA) system to the bioassay of growth hormone. The assay is based upon reduction of the yellow tetrazolium salt MTT to its purple formazan by lactogen-activated Nb2 rat lymphoma cells. The assay is precise and sensitive (detection limit 0.04 mU/L). Adaptation of the assay for the measurement of GH in patient sera was achieved by the use of a monoclonal anti-serum to prolactin and by dilution of patient serum to 0.625% or less to resolve complex serum effects. We aimed to compare bioactive and immunoactive GH concentrations in various clinical settings. We observed a greater increase in the bioactivity of GH when compared with an immunoassay (Hybritech IRMA) after intravenous administration of different doses of GHRH (0.005mg GHRH: increase in ESTA GH concentration 46mU/I compared with 17.5mU/L by IRMA; 0.05mg GHRH: increase in ESTA GH 30mU/L compared with 12.4mU/L by IRMA). Peak GH concentrations in response to intravenous insulin (0.15U/kg) also read differently (peak GH ESTA 119.9±5.9; IRMA 59.5mU/L). This discrepancy between bioactive and immunoactive GH concentrations was less pronounced with spontaneous GH peaks (GH ESTA 37.2±0.7; GH Hybritech 29.3 mU/L). Oxandrolone, a growth-promoting agent had minimal effect on bioactive:immunoactive (B:I) GH ratios in children with constitutional delay of growth and puberty (B:I ratio pre-oxandrolone 1.0; B:I on Oxandrolone 1.2). We conclude that subtle changes in the bio:immunoactivity of GH released in response to GHRH and insulin can be demonstrated in the ESTA bioassay. These changes may be of relevance in the interpretation of GH provocation tests.
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Dattani, M., Winrow, A., Pringle, P. et al. CLINICAL APPLICATION OF AN ELUTED STAIN ASSAY FOR THE MEASUREMENT OF GH BIOACTIVITY. Pediatr Res 33 (Suppl 5), S36 (1993). https://doi.org/10.1203/00006450-199305001-00200
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DOI: https://doi.org/10.1203/00006450-199305001-00200