Practical enzyme immunoassay for prolactin in human serum.

We have developed a competitive enzyme immunoassay for prolactin in human serum. Serum samples were incubated at 4 degrees C for 48 h with anti-prolactin antibodies and prolactin labeled with beta-D-galactosidase. The antibody-bound form of labeled prolactin was separated from the unbound form by a method based on the thiol-disulfide interchange reaction. By measuring the enzyme activity, serum prolactin could be determined. Sensitivity of the assay was 2.5 ng/ml, and the assay was as sensitive as radioimmunoassay. There was a good correlation between the values obtained by the enzyme immunoassay and those obtained by a radioimmunoassay (r = 0.98, slope = 1.26, y-intercept = - 12.8 ng/ml).