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This investigation was carried out to determine the factors affecting the low rates of implantation and parturition in superovulated adult rats.<BR>The first experiment was made to examine the number of ova shed after treatment with various doses of PMSG and hCG. The rats were pretreated with 10, 20, or 40 IU of PMSG and hCG at 15:00 hours (h) on the day of early or late diestrus, or at 11:00h on the day of late diestrus. Then the same or half dose of hCG was injected 42, 54, or 66 h later corresponding to normal proestrus LH surge, and killed 22h after hCG injection. The number of ova shed increased with increasing dose of PMSG. There were no significant difference in the number of ova shed among time intervals of PMSG and hCG, and between the same and half dose of hCG.<BR>In the second experiment, the rats were treated with 10, 20, or 40 IU of PMSG followed by same dose of hCG 54 h later. The females were placed with male and mating was confirmed the following morning by presence of spermatozoa in vaginal smear. They were killed 24, 48, 72, 96, or 120h after hCG injection, and the ovaries and uteri were washed by physiological saline to examine the fertility, transport and early development of ova and/or embryos. At 72h after hCG injection, the percentage of embryos recovered from uterus were increased with increasing doses of PMSG and hCG. The number of ova and/or embryos recovered were reduced with the lapse of time after hCG injection and increasing doses of PMSG and hCG, and the number of rats with ova and/or embryos were reduced in rats treated with 40 IU of PMSG and hCG 96 or 120h after hCG injection. When rats were examined 72 to 96h after hCG injection, the cleavage rate in gonadotrophin-treated rats was delayed as compared to untreated rats, and with increasing dose of hormone. At 24 to 72h after hCG injection, the fertility was lower in rats treated with 40IU of PMSG and hCG as compared to untreated, 10, or 20IU treated rats.<BR>These results suggested that the low rates of implantation and parturition in superovulated adult rats induced by high doses of PMSG and hCG may be due to a loss of ova and/or embryos from uterus by accelerated transport, although the low fertility and delay of development of ova and/or embryos were observed.
- 日本繁殖生物学会の論文
日本繁殖生物学会 | 論文
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