Neural Regulation of Urothelial Water Transport: Pelvic Nerve Stimulation Induces Aquaporin-2 and Vasopressin V1a Receptor Translocation in the Rat Urinary Bladder

Abstract

Purpose: Aquaporin-2 (AQP2) and vasopressin V1a receptor (AVP-V1a) are membrane proteins involved in water transport regulation in renal and extrarenal tissues. Their presence in the urinary bladder suggests a role in local water handling. This study aimed to investigate whether pelvic nerve stimulation induces translocation of AQP2 and AVP-V1a in the bladder urothelium of rats, thereby revealing a potential neural regulatory mechanism in water permeability. Methods: Forty female Sprague-Dawley rats were assigned to either a control (n=20) or electrical stimulation group (n=20). The pelvic nerve was exposed and stimulated at 10 V, 16 Hz, 0.8 msec for 60 seconds. Bladder tissues were harvested immediately and processed for immunohistochemistry and Western blotting to evaluate the localization and expression levels of AQP2 and AVP-V1a in cytosolic and membrane protein fractions. Results: Immunohistochemistry revealed that AQP2 and AVP-V1a were co-localized in the urothelium. Western blotting showed that pelvic nerve stimulation led to a significant decrease in cytosolic expression and a concurrent increase in membrane-associated expression of both AQP2 and AVP-V1a (P<0.05). These findings are indicative of protein translocation in response to neural stimulation. Conclusions: Pelvic nerve stimulation may trigger the relocalization of AQP2 and AVP-V1a from the cytosol to the membrane in bladder urothelial cells. This suggests a novel neurophysiological mechanism for modulating bladder water transport, with potential implications for understanding bladder homeostasis and dysfunction suggesting a possible role in regulating bladder water permeability.