Prostaglandin F2α concentrations in stallion semen and the effect of 24 hours of cold storage on exogenous prostaglandin F2α concentrations*
-H. O'Bert, M.A. Harris and M. J. Arns
Department of Animal Sciences, University of Arizona, Tucson, AZ USA 85721
Seminal plasma from several mammalian species has been shown to contain prostaglandin F2α (PGF2α). The seminal PGF2α is thought to function in uterine contractility and aid in uterine clearance and/or sperm transport. Concentrations of PGF2α vary by species and have been reported for most mammalian species. Seminal plasma, as well as exogenous PGF2α given intramuscularly or during intrauterine insemination has been shown to induce uterine contractility. Moreover, in sows, the inclusion of exogenous PGF2α in seminal extenders was shown to enhance fertility.
The present study was done to determine if PGF2α is stabile when included as a component of a stallion semen extender for use during cold storage.
Material and Methods
Single ejaculates from three mature stallions of known fertility were used to determine the concentration of PGF2α in whole ejaculates and to determine the stability of exogenous PGF2α during 24 h cold storage. Gel-free semen was processed and evaluated by standard procedures. An aliquot was frozen (-70 C) for commercial PGF2α analysis. A second aliquot was diluted with a skim milk-glucose extender to a final concentration of 25 million progressively motile sperm per ml. Two mg of PGF2α (Lutalyse, The Pharmacia-Upjohn Co., Kalamazoo, MI) were added to 10 ml extended semen and frozen for PGF2α analysis. A second sample containing 2 mg PGF2α was evaluated following cooling and storage in a static cooling device (Equine Express, Exodus Breeders Supply, York, PA). A Student's T Test was performed to determine treatment differences.
Results and Discussion
The mean (+ s.e.m) endogenous PGF2α was 97.86 (+ 59.2) ng/ml. This is higher than previously reported PGF2α concentrations for stallions (Claus et al., 1992). The differences may be due to the low numbers utilized in the current study. The endogenous concentrations of PGF2α varied between males (2.17 ng/ml to 202.73 ng/ml) and supports earlier reports of male variability in stallions, bulls and boars.
Mean PGF2α concentrations did not decline during 24 h of cold storage (226.1 + 11.6 μg/ml vs. 192.8 + 3.3 μg /ml; 0 and 24 h, respectively). This is similar to previously reported findings in the boar where PGF2α concentrations in PGF2α -enriched semen remained constant over a 72 h incubation at ambient temperature. The stability of the exogenous PGF2α when included in stallion semen extenders, suggests that it may be incorporated at the time of semen processing, rather than added following cold storage.
*Study to be presented at IX International Symposium on Equine Reproduction, August 2006