Uptake of sodium into rat isolated seminiferous tubules in vitro

The rate of 22Na uptake into isolated rat seminiferous tubules has been studied in vitro. The intracellular sodium exchanged rapidly with the outside sodium and within 26 min exposure to radiosodium, isotopic equilibrium was reached. The relationship between sodium influx at 2 min and external sodium concentrations was found to be linear suggesting that the entry of sodium into the seminiferous tubules is by simple diffusion. The intracellular Na+ concentration as measured by the 22Na taken up into the tubules at equilibrium condition was elevated in the absence of peritubular K+ and Ca2+ ions and treatment of the tubules with ouabain. No effects of amiloride and acetazolamide on the intracellular Na+ concentration were found. The significance of the 22Na uptake in relation to fluid secretion in the isolated seminiferous tubules was discussed.