Urea in the Seminiferous Tubule: Evidence for Active Transport

Abstract
Nephrectomized male rats were infused i.v. with [14C]-urea. The amount of radioactivity in subsequent micropuncture samples of cauda epididymal tubule (CET) fluids demonstrated a restricted movement of [14C]-urea into the CET. In the seminiferous tubules (SNT), radioactivity from [14C]-urea became higher than in blood plasma. 2,4-Dinitrophenol and ouabain inhibited this uphill movement of [14C]-urea, thus giving evidence for active transport of urea into the rat SNT.