Localization of oxytocin receptors in the human and macaque monkey male reproductive tracts: evidence for a physiological role of oxytocin in the male

The peptide oxytocin is present in tissues of the male reproductive tractfrom a variety of mammalian species. In the human, specific mRNA foroxytocin and the peptide itself have been identified in the testis,epididymis and prostate. The peptide has been shown to modulate bothsteroidogenesis and contractility in the male reproductive tract and may beinvolved in the pathogenesis of benign prostatic hyperplasia. We haveperformed Western blots and immunohistochemistry using a specific antibodyto the human oxytocin receptor (OTR) to investigate the distribution andlocalization of the receptor in the human and macaque monkey (Macacafasicularis). An immunoreactive band of approximately 55 kDa was detectedin human and monkey uterine, testicular and prostatic tissues and inpreparations of monkey caput and cauda epididymis. A second, less intense,band of 60 kDa was also seen in testicular and uterine tissue samples. Nospecific bands were detected in monkey muscle or in any tissue followingincubation with mouse immunoglobulin (Ig)M. In the human and monkey testisstaining for the OTR was present in the interstitial tissue and in Sertolicells. Localization of the OTRs varied throughout the epididymis beingexpressed by epithelial cells proximally but confined to cells at the baseof the epididymal ducts and to the surrounding smooth muscle layersdistally. In the prostate OTR were localized to the stromal tissuesurrounding the ducts. These findings correlate with sites of localproduction of the peptide and the observed biological actions of oxytocin,and thus support the evidence that oxytocin may play a physiological rolein the male reproductive tract.