Oxytocin Immunoreactivity in the Human Urethral (Littre's) Glands

Abstract

Abstract. Oxytocin is a cyclic nonapeptide whose best known effects are stimulation of uterine smooth muscle cells during labor and of milk ejection during lactation. Circulating oxytocin originates from the hypothalamus, but its production has also been documented in peripheral tissues. Furthermore, seminal plasma also contains oxytocin, but its functional role is still unknown, although its secretion is generally ascribed to the prostate. In this study, we investigated the possibility that seminal oxytocin is also secreted by other exocrine glands of the human male genital tract. Intramural (Littrè's) glands isolated from bioptic specimens of normal urethrae were processed for immunogold localization of oxytocin. Immunostaining was detected in principal cells, with gold particles specifically found on secretory granules. Basal and endocrine cells were unstained. The present findings suggest that urethral glands not only produce the mucinous layer that protects and lubricates the urethral wall, but also are potential sources of other seminal components, such as oxytocin, which probably play still unclear roles in reproductive physiology. Key words: Immunogold, Oxytocin, Urethral glands (J. Reprod. Dev. 56: [94][95][96][97] 2010) xytocin is a nonapeptide in which a disulfide bond between cysteine residues confers a cyclic structure. Its action is mediated by a transmembrane polypeptide receptor coupled with a G protein pathway, widely distributed throughout the human body [1,2]. Oxytocin is mainly studied as a hypothalamic hormone as well as vasopressin, from which it differs in two amino acids only. The best known biological effects of circulating oxytocin are those on female reproductive organs, such as stimulation of uterine contractions and of milk ejection. Moreover, effects on organs of the male genital tract have also been documented, such as penile erection and ejaculation [3,4]. In addition, a number of functions are thought to be regulated by local oxytocinergic systems, since oxytocin production has been documented in peripheral tissues [5]. In the male genital tract, paracrine secretion of oxytocin has been suggested in the testis, epididymis and prostate [1,6,7], where many functions such as cell growth, spermiation, steroidogenesis and muscle contraction could be affected [7][8][9][10]. Furthermore, seminal plasma also contains oxytocin, whose functional role still is uncertain [11][12][13]. This peptide is believed to originate from the prostate [1], but it could be also supplied by other sexual glands, which to date have not been examined in this regard. In this study, we show that the intramural glands of the human urethra (Littrè's glands) contain oxytocin-reactive material, suggesting the presence of the peptide in their exocrine secretions. Materials and MethodsSamples of the distal urethra were obtained from 4 patients aged 54-67 undergoing surgery for radical cystectomy at the Urologic Clinic of the University of Cagliari. The procedures were approved by the Local Ethics Committee, Unive...

The drug treatment of delayed ejaculation

“…It is involved in a wide variety of physiological and pathological functions including sexual activity, penile erection and ejaculation (103). The rationale for its use in DE may include the followings: (I) animal data suggest that sexual cues and behaviors stimulate central and peripheral OT neurotransmission which, in turn, facilitate copulation (104-106); (II) OT and its receptor have been identified in the human and animal male genital tract suggesting a role in regulation of contractility of these organs (107-111); (III) low dose systemic (intravenous or intraperitoneal) injection of oxytocin facilitates ejaculation in the laboratory animals (112-116); (IV) the pro-ejaculatory effects of systemic OT may be mediated via actions on peripheral OT or vasopressin (AVP) receptors that have been demonstrated in the testis, epididymis, vas deferens, prostate and penis of humans and animals, where they regulate the contractility of smooth muscle cells involved in ejaculatory process (117,118); (V) administration of OT receptor antagonists could inhibit or block these effects of OT multiple sites of action (118,119); (VI) treatment with OT restores the ejaculatory response but has no effect on the intensity of sexual excitement in male rats receiving fluoxetine indicating that SSRIs probably suppress ejaculatory responses by interrupting the action of OT (120); and (VII) men volunteers reported a feeling of decreased arousal and pleasure at orgasm on suppression of the systemic OT pulse by naloxone (121). In contrast to the findings of pro-ejaculatory effect in male rats, in the male prairie vole, OT causes an immediate cessation of all sexual activity which continues to remain so for at least 24 hr (122).…”