LOCALIZATION OF OXYTOCIN RECEPTORS IN THE HUMAN AND MACAQUE MONKEY MALE REPRODUCTIVE TRACTS - EVIDENCE FOR A PHYSIOLOGICAL-ROLE OF OXYTOCININ THE MALE

The peptide oxytocin is present in tissues of the male reproductive tr act from a variety of mammalian species. In the human, specific mRNA f or oxytocin and the peptide itself have been identified in the testis, epididymis and prostate. The peptide has been shown to modulate both steroidogenesis and contractility in the male reproductive tract and m ay be involved in the pathogenesis of benign prostatic hyperplasia. We have performed Western blots and immunohistochemistry using a specifi c antibody to the human oxytocin receptor (OTR) to investigate the dis tribution and localization of the receptor in the human and macaque mo nkey (Macaca fasicularis). An immunoreactive band of similar to 55 kDa was detected in human and monkey uterine, testicular and prostatic ti ssues and in preparations of monkey caput and cauda epididymis. A seco nd, less intense, band of 60 kDa was also seen in testicular and uteri ne tissue samples. No specific bands were detected in monkey muscle or in any tissue following incubation with mouse immunoglobulin (Ig)M, I n the human and monkey testis staining for the OTR was present in the interstitial tissue and in Sertoli cells. Localization of the OTRs var ied throughout the epididymis being expressed by epithelial cells prox imally but confined to cells at the base of the epididymal ducts and t o the surrounding smooth muscle layers distally. In the prostate OTR w ere localized to the stromal tissue surrounding the ducts. These findi ngs correlate with sites of local production of the peptide and the ob served biological actions of oxytocin, and thus support the evidence t hat oxytocin may play a physiological role in the male reproductive tr act.