A noncompetitive enzyme immunoassay for rat prolactin.

A sensitive and specific noncompetitive rat prolactin (rPRL) enzyme immunoassay (EIA) is described. In this assay, the same rabbit anti-rPRL antibody is both adsorbed to a solid-phase support, i.e. 96-well microtiter plates and conjugated covalently to peroxidase as a tracer. PRL being sandwiched between antibody molecules, the enzymatic activity is thus proportional to the amount of rPRL concentration. This assay was found highly specific for rat PRL and displayed a sensitivity of 12.5 pg/well (0.125 ng/ml) of NIH-RP2 equivalents. The intra-assay and inter-assay coefficients of variation were less than 10% over a wide range of rPRL concentration (0.25-40 ng/ml). This rPRL-EIA permits to quantify PRL in culture media or biological samples containing up to 25% of plasma. Comparison with a radioimmunoassay revealed a good correlation (r = 0.984, the slope = 1.04). This EIA is rapid, results being obtained within 4h30 or 18h30 depending on the nature of the biological samples. The tracer, easily performed with a low cost enzyme, can be stored for very long durations. Thus, this sensitive and rapid assay provides a valuable method for measuring rPRL.