A competitive enzyme immunoassay for follicle-stimulating hormone in ovine plasma using biotin-streptavidin amplification

To determine follicle-stimulating hormone (FSH) concentration in ovine plasma, a second-antibody enzyme immunoassay using biotin-streptavidin amplification (BS-EIA) was developed and was validated by comparison with a routine radioimmunoassay (RIA). Ovine FSH was labelled with D-biotinyl-epsilon-aminocaproic acid-N-hydroxysuccinimide ester (biotin-7-NHS). The minimum and maximum detection limits were 0.40 ng mL(-1) and 250 ng mL(-1) respectively in the BS-EIA. Plasma samples from three superovuiated ewes were measured for FSH by both BS-EIA and RIA. Correlation between values obtained by BS-EIA and RIA was 0.86 (n = 106), and the linear regression had a slope of 0.88 and an intercept of -0.07 (R-2 = 0.74). The baseline of BS-EIA was slightly lower than that of RIA (0.69 ng mL(-1) v. 1.10 ng mL(-1)). The intra-assay and inter-assay coefficients of variation in BS-EIA were 13.8% and 16.7% (n = 106) respectively. The recovery rates were 104.8+/-2.7% (mean+/-s.e.m, n = 14). changes in plasma FSH concentration from superovulated ewes evaluated by BS-EIA corresponded well with the results of routine RIA.