EFFECT OF HEPARIN ON CAPACITATION ACROSOME REACTION OF EQUINE SPERM/

The onset of sperm capacitation/acrosome reaction was evaluated using heparin. Equine semen was incubated at 38 degrees C for 4.5 h in cultu re medium with and without 10 mu g/mL heparin and with and without 0.1 mu M of Ca2+ ionophore. Sperm acrosome reaction was detected using ch lortetracycline fluorescence (CTC) and transmission electron microscop y (TEM). The CTC assay provided staining patterns that corresponded wi th the capacitation/acrosome reaction in other mammalian species (man, mouse, guinea pig). The percentages of uncapacitated sperm (PUC), cap acitated acrosome-intact sperm (PC), and acrosome-reacted sperm (PAR) were evaluated following incubation times of 0.5 and 4.5 h in heparin- free and heparinized medium, and at 4.5 h only in sperm exposed to Ca2 + ionophore. The CTC assay was highly correlated with TEM for estimati on of PAR. At 4.5 h, heparinized medium reduced PUC and increased PC a nd PAR, in comparison with heparin-free medium. Addition of Ca2+ ionop hore to the medium reduced PUC and increased PC and PAR at 4.5 h, as c ompared with sperm in ionophore-free medium. Incubation time also affe cted PUC, PC, and PAR in heparin-free and heparinized medium without i onophore. The PUC was greater at 0.5 h than at 4.5 h, and PC and PAR w ere less at 0.5 h than at 4.5 h. It would appear that the initiation o f capacitation/acrosome reaction of equine sperm in vitro is accelerat ed by heparin.