The prolactin gene is expressed in the mouse kidney

Background. Prolactin (PRL), originally identified as an anterior pituitary hormone exhibiting lactogenic activity, is now recognized as a versatile hormone expressed in a wide variety of tissues. Methods. In this study, the expression of PRL in the mouse kidney was investigated by solution-phase and in situ reverse transcription-polymerase chain reaction (RT-PCR) methods and immunohistochemistry. Results. Mouse PRL (mPRL) transcript and protein are localized in the parietal epithelial cells of Bowman's capsule. Pit-1 is a positive transcription factor for the expression of the PRL gene. The presence of Pit-1 transcript in the kidney was also assessed by RT-PCR methods. The localization of Pit-1 mRNA coincided well with that of PRL. Immunoreactivity to mouse PRL receptor (mPRL-R) is distributed on the luminal membrane of the proximal tubule cells and the parietal epithelial cells of Bowman's capsule. Conclusion. These data indicate that the parietal epithelial cells of Bowman's capsule synthesize PRL de novo and suggest that Pit-1 contributes to the transcriptional regulation of PRL gene expression in the kidney, and PRL expressed in this tissue functions in an autocrine/paracrine fashion.