Mechanosensitive Piezo1 channel in rat epididymal epithelial cells promotes transepithelial K⁺ secretion

The Piezo1 channel, a mechanosensitive channel that exhibit a preference for Ca²⁺, play multifarious physiological and pathological roles in the endothelium and epithelium of various tissues. However, the functional expression of Piezo1 channel in the epithelium of the male reproductive tract remains unknown. In the present study, the expression of Piezo1 channel in the rat epididymis was determined by real-time quantitative PCR, western blot and immunohistochemical analysis. Our data revealed that Piezo1 channel was located in the epithelial layer of the rat epididymis, with higher expression levels in the corpus and cauda regions. The pro-secretion function of Piezo1 channel was then investigated using short circuit current (I_SC) and intracellular Ca²⁺ imaging techniques. Application of Yoda1, a selective Piezo1 channel activator, stimulated a remarkable decrease in the I_SC of the epididymal epithelium. Pharmacological experiments revealed that the I_SC response induced by Piezo1 channel activation was abolished by pretreating epithelial cells with the Yoda1 analogue, Dooku1, the selective mechanosensitive cation channel blocker, GsMTx4, or removal of basolateral K⁺. Meanwhile, we demonstrated that activation of Piezo1 channel triggered a robust Ca²⁺ influx in epididymal epithelial cells. The possible involvement of Ca²⁺- activated K⁺channels (K_Ca) in transepithelial K⁺ secretion was then evaluated. And that big conductance K_Ca (BK), but not small conductance or intermediate conductance K_Ca, mediated Piezo1-elicited transepithelial K⁺ secretion. Moreover, we demonstrated that NKCC and NKA were responsible for supplying substrate K⁺ during transepithelial K⁺ secretion. These data demonstrate that the activation of Piezo1 channel promotes BK-mediated transepithelial K⁺ secretion, and thus may plays an important role in the formation of a high K⁺ concentration in epididymal intraluminal fluid.