CATALASE MESSENGER-RNA EXPRESSION IN THE MALE-RAT REPRODUCTIVE-TRACT

Reactive oxygen species (ROS) have been shown to impair sperm function . The actions of ROS are reduced by antioxidant enzymes, including cat alase. Although catalase-like activity has been demonstrated in semen, there has been no localization or characterization of catalase mRNA e xpression in the male reproductive tract. Catalase mRNA levels were ev aluated by northern blot analysis and in situ hybridization from the m ale reproductive organs of normal 60-day-old rats, testes of 10- to 90 -day-old rats, and testes of rats subjected to efferent duct ligation. Radioactive DNA probes were synthesized using a Klenow polymerase-bas ed specific primer synthetic procedure with a known published sequence for rat catalase. All tissues demonstrated a single transcript of 2.5 kilobases (kb). Low levels of catalase mRNA were detected in the norm al testis, epididymis, vas deferens, and prostate. No expression was d etectable with northern analysis in seminal vesicle. The levels of cat alase mRNA in reproductive organs were compared with the high levels o f expression detectable in rat liver. In the testis, catalase expressi on was primarily localized to peritubular and interstitial cells. In t he epididymis and prostate, mRNA was detected in the epithelium. The o bserved decrease in catalase mRNA levels in the maturing rat testis is consistent with its interstitial localization. The increase in testic ular catalase mRNA levels seen in parallel with progressive thinning o f the germinal epithelium after efferent duct ligation is also in keep ing with a peritubular or interstitial cell localization. The relative ly low levels of catalase mRNA expression in the normal adult male rep roductive tract undermine the role of catalase as a major antioxidant enzyme in these tissues. The low levels of catalase mRNA in the testis , and the undetectable levels in the seminiferous epithelium, however, imply that the germinal epithelium is predisposed to an oxidative sta te. These findings may help to explain the known susceptibility of the testis to oxidative stress.