Visualization of gene expression of short and long forms of prolactin receptor in rat reproductive tissues.

Prolactin receptor gene expression was visualized in various tissues by in situ hybridization. Probes specific to the intracellular domains of the short and long form of receptor were prepared. The specificity of these signals was controlled by competition with excess unlabeled homologous probes or heterologous probes; moreover, some tissues, such as penis and vagina, show no expression of either form of receptor mRNA. Macroautoradiogram signals (optical density) were quantified and expressed in arbitrary units. The long form of receptor mRNA was preferentially expressed in testis, epididymis, prostate, seminal vesicle, and mammary gland from lactating animals, whereas the expression of the two forms of mRNA was equivalent in ovary, uterus, and pregnant mammary gland. Signals were also localized at the light microscopic level to individual cells. This approach has permitted the precise localization of prolactin receptor mRNAs in reproductive tissues. Actions of prolactin have not been demonstrated in all tissues expressing receptor transcripts; thus it will be interesting to correlate the expression of long and short forms of receptor with specific functions.