Competitive enzyme immunoassay for bovine growth hormone

We developed an enzyme immunoassay (A) for bovine GH (bGH) which is based on indirect competitive immunoassay in culture medium from a bovine pituitary cell culture. 40 μl cell culture samples (or bGH standard) and bGH antibody (rabbit anti-bGH) were added to the 96 well microplate coated with secondary antibody (Goat anti-rabbit IgG), and incubated for 24 h at 37 °C. Biotin-label bGH was added and incubated further for 24 h at 37 °C, and biotinylated bGH was linked with streptoavidin-peroxidase. Substrates for peroxidase were added to the plate and incubated for 1 h at 4 °C. The enzyme reaction was stopped with 4N H₂SO₄, and the absorbency at 450 nm was measured with an ELISA Reader. The coefficients of intra-assay and inter- assay variations were 4.13-7.59% and 3.71-8.27%, respectively. The regression equation and correlation coefficients with the radioimmunoassay (RIA) were y(RIA) = 1.9986 x (EIA) - 1.3921 and 0.9701 (n=27), respectively. Collectively, the present assay provides a reliable alternative to RIA and offers the major advantage of eliminating radioactive reagents and counting equipment.