Hino Toshiaki, Oda Kanako, Nakamura Kenji, Toyoda Yutaka, Yokoyama Minesuke
Mitsubishi Kagaku Institute of Life Sciences (MITILS) Tokyo Japan.
National Research Center for Protozoan Diseases Obihiro University of Agriculture and Veterinary Medicine Hokkaido Japan.
Reprod Med Biol. 2009 Jul 22;8(4):157-161. doi: 10.1007/s12522-009-0024-y. eCollection 2009 Dec.
129 inbred mice show poor reproductive ability, as evidenced by small litters; however, the exact cause of this is unknown. In the present in vivo study we examined fertility and subsequent post-implantation development in an attempt to clarify the cause of small litter size in 129 mice.
129 or C57BL/6J females that displayed vaginal plugs 1 day after mating with males of the same strain were examined for the presence of fertilized eggs. Reciprocal matings were also performed between 129 and C57BL/6J mice. Subsequent post-implantation development of fertilized eggs was examined by dissecting females 18-19 days after the vaginal plugs were found.
Mean numbers of recovered eggs were 7.9 and 8.0 in 129 and C57BL/6J mice, respectively. Half of the recovered eggs were unfertilized in 129 mice, whereas all were fertilized in C57BL/6J mice. Mean numbers of live fetuses 18-19 days after mating were significantly lower in 129 mice (4.7) than in C57BL/6J mice (7.3). In different types of pairings using both strains of mice, the fertility was significantly lower whenever 129 females were used.
The small litter size in 129 mice is caused by low fertility resulting from female factors.
129品系近交系小鼠繁殖能力较差，表现为产仔数少，但确切原因尚不清楚。在本体内研究中，我们检测了生育力及植入后发育情况，以试图阐明129品系小鼠产仔数少的原因。
与同品系雄性小鼠交配1天后出现阴道栓的129品系或C57BL/6J品系雌性小鼠，检查是否存在受精卵。还在129品系和C57BL/6J品系小鼠之间进行了互交。通过在发现阴道栓后18 - 19天解剖雌性小鼠，检查受精卵植入后的发育情况。
129品系和C57BL/6J品系小鼠回收的卵的平均数量分别为7.9个和8.0个。129品系小鼠回收的卵中有一半未受精，而C57BL/6J品系小鼠的所有卵均已受精。交配后18 - 19天，129品系小鼠的活胎平均数量（4.7个）显著低于C57BL/6J品系小鼠（7.3个）。在使用这两个品系小鼠的不同配对类型中，只要使用129品系雌性小鼠，生育力就显著较低。
129品系小鼠产仔数少是由雌性因素导致的低生育力引起的。
