EFFECT OF HEPARIN ON THE IN-VITRO FERTILI ZING ABILITY OF GOAT SPERMATOZOA AS ASSESSED BY HETEROLOGOUS SOLUBILIZED ZONA PELLUCIDAE

Heparin has been shown to improve the fertilizing ability of goat sper matozoa in a dose-dependent manner. The present study assessed the mec hanism involved in the stimulatory effect by using solubilized zona pe llucidae from bovines. Bovine cumulus-oocyte complexes were matured in 199 plus serum and insuline. Thereafter, oocytes were denuded from gr anulosa cells and used either to obtain zona pellucidae or for fertili zation. Free zonae were collected by mechanical means, solubilized in heated acetic acid, liofilized and stored at -20 degrees C until their reconstitution in Talp plus serum. In Experiment 1, spermatozoa were suspended either in non-capacitated conditions or in Talp plus heparin and Talp plus heparin and zonae, and incubated for 90 min at 39 degre es C in 5% CO2 in air. In Experiment 2, spermatozoa were grouped as be fore and co-incubated with matured oocytes for 18 hr to assess their f ertilizing ability. In Experiment 3, spermatozoa were suspended either in seminal plasma, Talp plus heparin or Talp without heparin for 90 m in. At 0, 45 and 90 min, semen samples were exposed to solubilized zon ae and were further incubated for 30 min. Acrosome disruption in Exper iment 1 and 3 was assessed by staining spermatozoa with PI/PSA. Fertil ization in Experiment 2 was verified by the presence of pronuclei and sperm tail. The results in Experiment 1 showed that the acrosome disru ption rate increased above the control groups after 90 min of incubati on only in zonae-treated spermatozoa (P<0.001). In Experiment 2, ferti lization was seen only when spermatozoa were previously incubated in c onditions known to capacitate them. In Experiment 3, the results showe d that the acrosome disruption rate first increased when spermatozoa w ere exposed to zonae after 45 min of incubation (P<0.01). The cumulati ve results suggest that heparin improves fertilization by stimulating sperm capacitation. The effect is expressed after 45 min of sperm incu bation.