Expression of Aquaporin Water Channels in Rat Vagina: Potential Role in Vaginal Lubrication

Abstract

Introduction Aquaporins (AQPs) are membrane proteins that facilitate water movement across biological membranes. There has been little research on the role of AQPs in the female sexual arousal response. Aim The purposes of this study were to investigate the localization and functional roles of AQP1, AQP2, and AQP3 in rat vagina. Methods Female Sprague-Dawley rats (230–240 g, N=20) were anesthetized. The vaginal branch of the pelvic nerve was stimulated for 60 seconds (10 V, 16 Hz, 0.8 ms), and the animals were sacrificed either immediately or 5 minutes later. The expression and cellular localization of AQP1, 2, and 3 were determined by Western blot and immunohistochemistry of the vagina. The intracellular membrane and plasma membrane fractions of the proteins in vaginal tissue were studied by immunoblot analysis with the differential centrifugation. Main Outcome Measures The expression and cellular localization of AQPs, and pelvic nerve stimulation induced translocation of AQPs in rat vaginal tissue. Results Immunolabeling showed that AQP1 was mainly expressed in the capillaries and venules of the vagina. AQP2 was expressed in the cytoplasm of the epithelium, and AQP3 was mainly associated with the plasma membrane of the vaginal epithelium. AQPs were found to be present primarily in the cytosolic fraction of untreated tissues. The translocation of AQP1 and 2 isoforms from the cytosolic compartment to the membrane compartment was observed immediately after nerve stimulation and had declined at 5 minutes after nerve stimulation, while the subcellular localization of AQP3 was not changed by nerve stimulation. Conclusions These results showed a distinct localization of AQPs in the rat vagina. Pelvic nerve stimulation modulated short-term translocation of AQP1 and 2. These results imply that AQPs may play an important role in vaginal lubrication.

Impact of Sacral Neuromodulation on Female Sexual Function and His Correlation with Clinical Outcome and Quality of Life Indexes: A Monocentric Experience

“…Improvement in FSF after SNM is reported to vary from 41.2% to 78% [20–23], though these studies have involved a small number of patients and short follow‐up periods. Only one study reported that neuromodulation did not significantly improve FSF in a heterogeneous population including patients with OAB and painful bladder syndrome (PBS) [24]. Lombardi et al., in a prospective study with a follow‐up of 22 months, reported a 25% and 36.3% enhancement of sexuality in idiopathic and neurogenic patients, respectively [25].…”

All-Trans Retinoic Acid Increases Aquaporin 3 Expression in Human Vaginal Epithelial Cells

“…AQPs have been suggested to play an important role in vaginal lubrication 9 . In our previous animal study, we suggested a role for AQPs in vaginal lubrication by demonstrating the expression of AQP1, 2, and 3 in rat vagina 9, 21.…”

“…In our previous animal study, we suggested a role for AQPs in vaginal lubrication by demonstrating the expression of AQP1, 2, and 3 in rat vagina 9, 21. We suggested that sexual stimulation by electric stimulation of the pelvic nerve might be involved in moving the AQP channel from the cytoplasm to the cell membrane of the epithelium and that this alteration might induce water transport across the vaginal cells.…”

“…Among the AQP family members, AQP3 transports glycerol and presumably other small solutes across cells 7, 8. Vaginal fluid consists of various elements besides water, and we previously reported the distinct localization of AQPs in the vagina of rats and humans as a potential component of vaginal lubrication 9, 10. Thus, we targeted AQP3 as a potential active mediator of vaginal lubrication.…”

Effects of castration on the expression of aquaporins and apoptosis in the ventral prostate

“…In the current study, AQP1 was expressed on the capillaries and venules, but was not expressed on the membranes of the epithelium. According to studies on other reproductive tract organs, AQP1 has also been identified in the subepithelial capillaries and venules of the vagina and epididymis [14][15][16]. Therefore, AQP1 may not be mainly localized to the plasma membranes of epithelial cells of the prostate.…”