PROLACTIN AND PROLACTIN RECEPTORS ARE EXPRESSED AND FUNCTIONING IN HUMAN PROSTATE

Prolactin is widely expressed in different tissues, and it is presumed to have both local and systemic actions. In males it is known to infl uence reproductive functions but the significance and mechanisms of pr olactin action in male accessory reproductive tissues are poorly under stood. Here we show that prolactin acts as a direct growth and differe ntiation factor for human prostate, as measured by changes in DNA synt hesis and epithelial morphology of organ cultures. Furthermore, we rep ort the expression in human prostate of a short prolactin receptor for m in addition to the long form, based upon ligand cross-linking studie s and RT-PCR analysis of mRNA expression, The highest density of prola ctin receptors was detected in the secretory epithelial cells by immun ohistochemistry. Finally, we report that prolactin is locally produced in human prostate epithelium, as evidenced by marked prolactin immuno reactivity in a significant portion of prostate epithelial cells, with parallel expression of prolactin mRNA in human prostate. Collectively , these data provide significant support for the existence of an autoc rine/paracrine loop of prolactin in the human prostate and may shed ne w tight on the involvement of prolactin in the etiology and progressio n of neoplastic growth of the prostate.