Prolactin receptor gene expression and immunolocalization of the prolactinreceptor in human luteinized granulosa cells

Prolactin is mainly known for its role in breast development and lactation, but has been also implicated in other physiological functions such as immu noregulation and ovarian steroid production. Although prolactin and prolact in receptor (PRL-R) transcripts have been previously identified in the huma n ovary, the spatial localization of the receptor is unknown. To investigat e the presence of PRL-R within the follicular apparatus, human luteinized g ranulosa cells were obtained at the time of follicular aspiration from wome n undergoing ovarian stimulation for IVF. RNA extracted from these cells wa s subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) usi ng specific primers for the PRL-R gene. In addition, paraffin sections of i solated granulosa cells and sections of premenopausal human ovaries were im munostained with a mouse anti-human PRL-R monoclonal antibody. PRL-R were i mmunolocalized to the cell membrane of isolated luteinized granulosa cells and PRL-R transcripts were detected in the extracted RNA. No detectable sta ining was noted in secondary and early antral follicles in archived paraffi n sections. These findings confirm the presence of PRL-R in human luteinize d granulosa cells and suggest a localized role for PRL within the mature fo llicle. The absence of PRL-R in the early follicle suggests that the effect s of prolactin are exerted around the time of ovulation.