Glutathione-Independent Prostaglandin: DISCUSSION(5)
The role of PGDS in all the fluids of the genital tract is uncertain. No information is available in vivo about enzyme activity of the secreted luminal PGDS. However, PGD2 can be formed in vitro by glutathione-independent PGDS in rat epididymal tissue homogenates, and thus it is probable that PGDS is potentially active in the epididymis. Bull testicular, epididymal, and seminal isoforms have been found to be capable of transforming PGH2 to PGD2 in the fluids after dilution. However, the authors of this work suggested that an unknown inhibitor of PGDS may exist in vivo, at least in bull seminal plasma. Furthermore, the structural modifications observed in the ram and stallion when the protein passes through the epididymis (loss of about 5 kDa in both species and an increase in pI in the ram) may also alter the properties of this enzyme, as has been shown for other epididymal enzymes such as gamma-glutamyl transpeptidase during transit. ampicillin antibiotic
The substrate of PGDS, PGH2, is produced from arach-idonic acid by cyclooxygenases, also known as prostaglandin G/H synthases, that have been described in at least two isoforms, termed COX-1 and COX-2. No information is available about the presence or concentration of PGH2 in either the RTF or the epididymal fluid. However, prostaglandin G/H synthase has been localized in the epithelium of the anterior part of the mouse epididymis, suggesting that PGH2 should be formed by the epididymal epithelium in the region where PGDS is secreted.