A quantitative comparison of the passage of capacitated and uncapacitated hamster spermatozoa through the uterotubal junction.

Female hamsters were artificially inseminated at the time of ovulation with an equal concentration and volume of capacitated sperm suspension in one uterus and uncapacitated sperm suspension in the contralateral uterus. When oviducts were examined 3.5-4.0 h after insemination, a significantly (paired t-test, p less than 0.05) lower number of spermatozoa were found in the oviduct from the side inseminated with capacitated sperm suspension compared to the side inseminated with uncapacitated sperm suspension. The reduction in the number of spermatozoa entering the oviduct on the side inseminated with capacitated sperm suspension was particularly evident when nearly all the spermatozoa in the suspension were hyperactivated. These results suggest that hamster spermatozoa require a progressive linear type of motility pattern to pass efficiently through the uterotubal junction and that under normal conditions in vivo, fertilizing spermatozoa initiate hyperactivated motility after entering the oviduct.