Expression of cyclooxygenase-2 in rat testis.

Cyclooxygenase, the rate-limiting enzyme in the production of prostaglandins, exists in two isoforms, the constitutive cyclooxygenase 1 (Cox-1) and the inducible cyclooxygenase 2 (Cox-2). Cox-1 is involved in homeostatic functions while Cox-2 is implicated in various pathological processes such as inflammation and cancer. The present study describes the constitutive expression of Cox-2 in immature and mature rat testis, primarily localized in the spermatogonial cells. An interesting observation is the presence of Cox-2 on the chromatin and also in cytosol, apart from nuclear and endoplasmic reticular membranes. The significance of this observation is not yet clear, though its presence in the nucleus raises the possibility of Cox-2 having a more direct role in gene regulation than was thought earlier. In addition, the Cox-2 mRNA in testis is the smaller (2.8 kb) of the two isoform transcripts reported for Cox-2. Further hormone treatment regimes (testosterone/follicle stimulating hormone) increased the levels of Cox-2 protein within 6 h after treatment, suggesting that the sustained levels of Cox-2 protein in testis can be further influenced by gonadotrophins and androgens.