Received April 28, 1998
Accepted May 17, 1998

Introduction:We studied whether sperm preparation by swim-up technique can select a better intact acrosome sperm population and analyzed how subsequent in vitro capacitation influenced the acrosomal status of these selected spermatozoa. Material and Methods:Semen specimens from normal donors (n=15) were divided into three equal aliquots:the first received no treatment(raw; contro l) and the others were processed by swim-up technique. After swim-up, the second aliquot received no further treatment (swim-up) and the third was capacitated in air for 3hours by incubation in a modified BWW with 3% HSA at 37°C under 5 % C02(capacitated). Sperm motion parameters in raw, swim up and capacitated specimens were anaIyzed by CASA. The acrosome status was assessed by FITC-PNA lectin. Sperm viability was measured by Hoechst-33258stain . Results:Percent sperm motility, percent viability and ali motion parameters, except linearity, were significantly increase in both swim-up and capacitated specimens. The frequency of spermatozoa exhibiting intact acrosomes was not different between raw and swim-up specimens(p=0.63). However, the frequency of acrosome reacted spermatozoa was significantly higher in the capacitated group (20.5%) compared to both raw and swim-up groups(p<0.0001). Acrosome reaction was observed in 13.1% and 13.0% of raw and swim-up spermatozoa, respectively, and this has occurred independent of capacitation. Conclusions:We conclude that sperm preparation by swim-up technique does not select a better acrosome intact sperm population in spite of yielding a highly motile and viable one.In addition, in vitro sperm capacitation significantly optimizes the acrosome reaction rate. However, a small proportion of sperm do not require capacitation to undergo in vitro spontaneous acrosome reaction.