Objective: To investigate intraovarian prolactin and prolactin-receptor gene expression and to assess local prolactin synthesis with emphasis on possible differences between premenopausal and postmenopausal status.
Design: The RNA extracted from human premenopausal and postmenopausal tissues was subjected to reverse transcription and polymerase chain reaction by using prolactin-specific intron- and exon-spanning primers. Prolactin-receptor expression was investigated accordingly. The amplified complementary DNA fragments were analyzed by gel electrophoresis and restriction enzyme mapping. Local prolactin hormone synthesis was verified by a time-resolved immunofluorometric assay based on our monoclonal antibodies.
Result(s): Prolactin and prolactin-receptor gene expression was observed in all analyzed human ovaries (n = 18). Several other human tissue specimens, such as lung and kidney, served as negative control tissues. Significantly elevated concentrations of prolactin were detected in cytosolic extracts of premenopausal (n = 6; mean +/- SD; 20.6 +/- 3.3 ng/g tissue wet weight) versus postmenopausal (n = 6; 3.6 +/- 3.0 ng/g tissue wet weight) ovaries.
Conclusion(s): The human ovary not only serves as a target for endocrine prolactin action but also as a site of local prolactin hormone production. In agreement with previous reports on extrapituitary sources of prolactin, we consider prolactin as a hormone as well as an autocrine or paracrine growth or regulatory factor. Significantly increased concentrations of prolactin in premenopausal ovarian tissue verifies its role in human reproduction.