The transepithelial movement of 3H-3-O-methyl-d-glucose in the hamster seminiferous and cauda epididymidal tubules

Abstract

Studies were performed in male hamsters to determine whether antiluminal, active glucose transport played a role in maintaining low glucose concentrations in male reproductive tract fluids. Studies of tissue uptake of 3H-3-O-methyl-D-glucose (3H-3OMG) demonstrated that after equilibrium seminiferous tissue 3H-3OMG concentrations were similar to blood plasma concentrations. Previous studies have shown that under similar circumstances seminiferous tubule lumen fluid 3H-3OMG concentrations are much lower than blood plasma concentrations. These facts suggested the possible presence of an antiluminal, active transport system for glucose in the seminiferous epithelium. In vivo perfusion of seminiferous tubules with fluids containing 3H-3OMG demonstrated an approximately 80% removal of the isotope after 1.5 hours. This movement was against a blood-lumen glucose gradient and was consistent with antiluminal active glucose transport. Increasing phloridzin concentrations in intraluminal perfusion fluid tended to be associated with decreased removal of 3H-3OMG from the lumen fluid; however, this effect was not significant; thus the evidence failed to support a hypothesis of an active antiluminal glucose pump in the seminiferous epithelium. Movement of 3H-3OMG across the cauda epididymidal epithelium was limited in both the pro- and antiluminal direction. The blood-epididymal barrier for 3H-3OMG movement appears to be much more restrictive than the blood-seminiferous tubule barrier for the same molecule.