OXIDATIVE STRESS DIFFERENTIALLY REGULATES THE EXPRESSION OF GAMMA-GLUTAMYL-TRANSPEPTIDASE MESSENGER-RNAS IN THE INITIAL SEGMENT OF THE RAT EPIDIDYMIS

Reactive oxygen species (ROS) have a powerful cytotoxic effect on sper matozoa and have been implicated in spermatozoal dysfunction and male infertility. gamma-Glutamyl transpeptidase (GGT) is essential to the m etabolism of the antioxidant glutathione and, as such, is believed to be important in protecting spermatozoa against oxidative stress. The a ims of this study were 1) to establish in vitro conditions in which RO S were generated and 2) to determine whether oxidative stress regulate d the expression of GGT mRNAs I-IV in the initial segment of the epidi dymis. Initial segments were collected from adult male rats and incuba ted in culture media to which ROS-generating compounds, hypoxanthine a nd xanthine oxidase, were added. By 6.5 hours, incubation of tissue in high-oxidative stress conditions caused a 56% decrease in reduced glu tathione concentration, a concomitant 240% increase in oxidized glutat hione concentration, and a 25% decrease in adenosine triphosphate conc entration. RNase protection analyses demonstrated an approximate 70% u p-regulation of GGT mRNAs II-IV in a differential manner, depending on the concentration of oxidizing agents and the type of ROS generated. gamma-Glutamyl transpeptidase mRNA I was not expressed. These results support the hypothesis that expression of GGT mRNAs is regulated by ox idative stress in the initial segment of the rat epididymis.