Glutathione-Independent Prostaglandin: DISCUSSION(3)
The presence of PGDS in ram and stallion epididymal fluids was related not only to epididymal activity but also to testicular activity, as it was detected in the RTF. This protein has also been found in the RTF of the bull. However, testicular PGDS has more acidic isoforms than the epididymal protein. As only one glutathione-independent PGDS gene has been observed to date, this polymorphism is probably due to differential degrees of gly-cosylation of the protein between tissues. Variations in the degree of glycosylation of PGDS have been found between blood and brain PGDS (p-trace protein) in humans. Such variations in protein glycosylation between the testis and the epididymis have also been found for other proteins secreted by the two organs, such as clusterin. Cheap Diskus Advair
As for PGDS, the isoforms of testicular clusterin are more acidic than the epididymal isoforms. In the stallion, the acidic isoforms of PGDS found in the first part of the epididymis were not found to be secreted by the epididymal epithelium, and they corresponded to the acidic testicular PGDS secretion that was not reabsorbed. Indeed, these isoforms were not observed in the caput epididymal fluid when the testicular fluid was prevented from entering the epididymis by efferent duct ligation. In the ram, the acidic testicular form was not found in the anterior part of the epididymis; it was probably all resorbed. Expression of PGDS mRNA (p-trace mRNA) in the testis has been detected in Leydig cells in the mouse and in cells within the seminiferous tubules in men. A germ cell origin of PGDS is highly improbable, since PGDS is still found in the RTF of azoospermic rams (unpublished results).