Glutathione-Independent Prostaglandin: DISCUSSION(6)
Another potential source of PGH2 may be the spermatozoa themselves, since cyclooxygenases have also been localized in the male gamete. The hypothesis of a sperm PGH2 origin is reinforced by the fact that arachidonic acid (the substrate of COX activity) can be released from sperm membranes by phospholipase A2 during the loss of phospholipids as the gametes transit the epididymis. These hypotheses have to be investigated. antibiotics levaquin
PGDS is the only one of the lipocalins that is associated with enzyme activity. The lipocalin family consists of various small secretory proteins that share a common feature of binding and transport of lipophilic molecules. PGDS may act as a transporter of lipophilic substances, including prostaglandins. Moreover, PGDS was suggested to be a retinoid transporter with an affinity for retinoic acid as great as that of retinoic acid-binding protein. However, in the epididymis this function is more probably performed by the epididymal retinoic acid-binding protein that is secreted from the corpus to the cauda epididymidis in mammals.
Another role in the maturation and maintenance of blood-tissue barriers has been proposed for PGDS, which is highly and specifically expressed in fluids protected by a blood-tissue barrier such as cerebrospinal fluid and male genital excurrent duct fluids.
The relationship between PGDS and the physiology of spermatozoa is unknown, but a relationship between this protein and the fertility of animals has recently been described. This protein does not seem to bind to sperm membranes with high affinity, since it has not been detected in sperm membrane extracts obtained after sperm washing (personal results). However, this lack of sperm binding does not exclude potentially low-affinity interactions that could occur in the presence of the high concentration of PGDS in the caput epididymal fluid.
In fact, the wide distribution of this enzyme in the genital tract more probably has a continuous effect on the gamete, or on its surroundings, than a regionalized action on the sperm, as appears to be the case for epididymal sperm maturation processes.