Effect of alpha-tocopherol on plasma testosterone and plasminogen activator activity or inhibition in ram spermatozoa

The objective of this study was to evaluate the effect of alpha-tocopherol on blood testosterone and specific proteolytic enzymes in spermatozoa and seminal plasma, with final aim the increase of sperm fertilizing ability with a nutritional supplement. The effect of alpha-tocopherol supplementation on testosterone parameters (mean value, basal level, peak number, mean concentration value during peaks, peak amplitude, peak duration) and plasminogen activator activity (PAA), plasminogen activator inhibition (PAI) and plasmin inhibition (PI) of spermatozoa and seminal plasma was studied in the ram during autumn (estrous period for the sheep in Greece) and spring (anestrous period). Treated animals showed a marked increase in serum alpha-tocopherol. Testosterone parameters were not affected by the alpha-tocopherol in either autumn or spring, however, the spermatozoal PAA and PAI (anti-tPA) were increased in the spring but not in autumn. These enzymes and their inhibitors are normally increased in autumn (the breeding season) and low in spring. If PAA can improve the fertilizing ability of spermatozoa in the spring, our finding may mean that a nutritional supplement, such as alpha-tocopherol, could provide rams for an accelerated onset of the breeding season in the ewe.