Human follicular fluid: prolactin is biologically active and ovum fertilization correlates with estradiol...

The bioactivity of prolactin (PRL) in follicular fluid (FF) obtained from mature preovulatory follicles was measured by the Nb2 lymphoma-cell bioassay and compared with the immunoreactivity as measured by radioimmunoassay (RIA-PRL). There was a good correlation between the two assay systems (P less than 0.01), and when RIA-PRL was more than 25 ng/ml, both assay systems yielded comparable values, with a mean bioassay/RIA ratio of 1.06 +/- 0.03; however, when RIA-PRL was 25 ng/ml or less, a discrepancy between the two assay systems was evident, with a bioassay/RIA ratio of 1.55 +/- 0.15. The estradiol (E2) concentration of FF obtained from follicles that contained oocytes which were subsequently fertilized was greater than that in follicles containing oocytes which were not fertilized: 588 +/- 62 vs 376 +/- 37 ng/ml (P less than 0.01), respectively. No differences were found in bioassay-PRL, RIA-PRL, progesterone (P), and FF volumes between fertilized and unfertilized groups of follicles. FF from mature preovulatory follicles contained greater concentrations of RIA-PRL compared to immature follicles (34.6 +/- 3.1 vs 8.5 +/- 1.6 ng/ml; P less than 0.001).