Motility of Rabbit Spermatozoa in the Secretions of the Oviduct

Abstract

The contents of the isthmus of the rabbit oviduct were recovered by flushing with mineral oil at 4 h postcoitus (p.c.) and at 11 h p.c. The movement of isthmic spermatozoa in native fluid was assessed visually and was uniformly nonprogressive and “vibratory” in quality at both recovery times. In a second series of experiments, contralateral isthmi were flushed with fresh rabbit ampullar fluid and with in vitro fertilization medium. Sperm motility in these flushings was assessed by high speed cinemicrography. The flagellar beat frequency of isthmic sperm in ampullar fluid was initially low but increased significantly during 4 h incubation in vitro. When culture medium was used for flushing, the beat frequencies of isthmic sperm were approximately twice those of sperm recovered in ampullar fluid and equal to frequencies attained by the latter during in vitro incubation. The percentage of activated sperm was low in all populations recovered at 11 h p.c. and did not increase during in vitro incubation. When sperm were recovered in ampullar fluid at 4 h p.c., the percentage activation increased from 6.7% to 34% during incubation in vitro. When recovered in culture medium at 4 h p.c., more than 50% of the isthmic sperm were immediately activated. These observations support the hypothesis that the environment of the lower oviduct may induce a reversible reduction in sperm flagellar beat frequency. They also suggest that sperm resident in the oviductal isthmus prior to ovulation can be stimulated to undergo activated motility, while those remaining in the isthmus after ovulation are no longer able to respond.