Acrosome Reaction of Bovine Spermatozoa In Vivo: Sites and Effects of Stages of the Estrous Cycle 1

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Abstract
Thirty-two cows were inseminated near the uterotubal junction at various stages of the estrous cycle and slaughtered 16 h later to determine the effects of stage of the estrus cycle and tubal site of sperm recovery on the frequency of acrosome-reacted bull spermatozoa. Slaughter times were 46, 70, 144 or 168 h after each cow was injected with prostaglandin (PG)F2.alpha. or during the luteal phase of the estrus cycle. Sperm were recovered from the upper uterus and the isthmus and ampulla of the oviducts and stained for both viability and acrosome reaction. The highest frequency of acrosome-treated sperm was found in the ampulla ipsilateral to a dominant follicle (largest follicle present) or recent ovulation and primarily at 70 h after PGF2.alpha. (P < 0.05). Fewer sperm were acrosome reacted prior to (46 h post-PGF2.alpha.) and well after (168 h post-PGF2.alpha.) estrus than during or immediately postestrus (70, 90 and 144 h post-PGF2.alpha.; P < 0.05). Except for 2 cows, 1 at 46 h and 1 at 70 h, all cows with more than 50% acrosome-reacted sperm in the ampulla had ovulated before slaughter. Capacitated sperm evidently become localized in the ampulla of the oviduct of the ovulatory side around the time of ovulation.