Small Animal Clinic, Veterinary University Hannover, Foundation, Bünteweg 15, 30559, Hannover, Germany.
Acta Vet Scand. 2012 Aug 29;54(1):49. doi: 10.1186/1751-0147-54-49.
Unlike other domestic mammals, in which metaphase-II oocytes are ovulated, canine ovulation is characterized by the release of primary oocytes, which may take 12 to up to 36 hours. Further 60 hours are needed for maturation to secondary oocytes which then remain fertile for about 48 hours. Oestrus takes 7 to 10 days on average and may start as early as a week before ovulation. This together with the prolonged process of post-ovulatory oocyte maturation requires an according longevity of spermatozoa in the female genital tract in order to provide a population of fertile sperm when oocytes have matured to fertilizability. Therefore the distribution and viability of spermatozoa in the bitch genital tract was examined during post-ovulatory oocyte maturation.
Thirteen beagle bitches were inseminated on the day of sonographically verified ovulation with pooled semen of two beagle dogs containing one billion progressively motile spermatozoa. Ovariohysterectomy was performed two days later (group 1, n = 6) and four days later (group 2, n = 7). The oviduct and uterine horn of one side were flushed separately and the flushing's were checked for the presence of gametes. The oviducts including the utero-tubal junction and the uterine horns, both the flushed and unflushed, were histologically examined for sperm distribution.
The total number of spermatozoa recovered by flushing was low and evaluation of viability was limited. Prophase-I oocytes were collected from oviduct flushing in group 1, whereas unfertilized metaphase-II oocytes were detected in group 2. From day 2 to day 4 after ovulation a significant decrease in the percentage of glands containing sperm (P<0.05) and a marked reduction of the mean sperm number in uterine horn glands were observed. A concomitant diminution of spermatozoa was indicated in the utero-tubal junction accompanied by a slight increase in sperm numbers in the mid oviduct.
Oocyte maturation to metaphase-II stage is accompanied by a continuous sperm detachment and elimination in the uterine horns. Entrance of spermatozoa into the caudal oviduct seems to be steadily controlled by the utero-tubal junction thus providing a selected sperm population to be shifted towards the site of fertilization when oocyte maturation is completed.
与其他国内哺乳动物不同，犬类的排卵特征是初级卵母细胞的释放，这可能需要 12 至 36 小时。进一步需要 60 小时才能成熟为次级卵母细胞，然后这些次级卵母细胞保持受精能力约 48 小时。发情期平均持续 7 至 10 天，可能早在排卵前一周就开始了。这加上排卵后卵母细胞成熟的过程漫长，需要在雌性生殖道中精子的相应寿命，以便在卵母细胞成熟到可受精能力时提供一群有生育能力的精子。因此，在排卵后卵母细胞成熟过程中，检查了母犬生殖道中精子的分布和活力。
13 只比格犬在超声证实排卵当天用两只比格犬的混合精液进行授精，精液中含有 10 亿个渐进式运动的精子。两天后（第 1 组，n = 6）和四天后（第 2 组，n = 7）进行卵巢子宫切除术。一侧的输卵管和子宫角分别冲洗，检查冲洗液中是否有配子。对输卵管（包括输卵管-子宫连接部）和子宫角（冲洗和未冲洗）进行组织学检查，以检查精子分布。
冲洗回收的精子总数较低，且活力评估受到限制。第 1 组从输卵管冲洗中收集到了前期 I 期卵母细胞，而第 2 组则检测到了未受精的中期 II 期卵母细胞。排卵后第 2 天至第 4 天，含精子的腺体百分比显著下降（P<0.05），子宫角腺体中的平均精子数量明显减少。在输卵管-子宫连接部，精子数量减少，同时在中输卵管，精子数量略有增加。
卵母细胞成熟为中期 II 期伴随着子宫角中精子的连续脱离和消除。精子进入输卵管尾端似乎受到输卵管-子宫连接部的稳定控制，从而为卵母细胞成熟完成时向受精部位转移提供了一个精选的精子群体。
