Distribution of Na, K-ATPase in the epididymis and its control by androgen

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The epididymal fluid has unique composition of ion, which is much different from the extracellular fluid. Toknow the mechanism of the formation of the ion composition in the epididymis, we studied the localization of Na, K-ATPase in 12-week-old Sprague Dawley rat epididymis and human epididymis. Immunohistochemical staining using a polyclonal antibody specific forthe alpha-subunit of rat kidney Na, K-ATPase demon strated that Na, K-ATPase was expressed at high levels on the basolateral membrane of the chief cells in all regions of the rat and human epididymal epithelium.To study the action of androgen on the epididymal Na, K-ATPase, the expression of Na, K-ATPase was evaluated in rats treated with Gn RH analog (chemical castration) using immuno histochemistry and Western-blotting an alysis. Although there was no difference in the immun or eactivity of Na, K-ATPase between the castrated and control groups, the Western-blotting analysis demonstrated that the quantity of Na, K-ATPase in the caput epididymis decreased in the castrated group compared to the control group. Castration showed no effects on the quantity of Na, K-ATPase in the corpus or cauda epididymis.Our study showed that the ion composition of the epididymal fluid was probably created by Na, K-ATPase in the epididymal epithelium and that the expression of Na, K-ATPase in the caput epididymis was controlled by androgen.