To investigate the effects of clorniphene citrate(CC) on estradiol-induced LH surge in rats, serum levels of estradiol and LH and the number of oocvtes ovulated were measured in two groups of immature rats. The rats in control group were treated with 4 lU PMSG on the 28th day of age, and CC treatment group were treated with CC(Img/day) for 3 days starting at the age of 25 days followed by 4 IU PMSG on the 28th day of age. Animals were sacrificed .at 48,. 60, 72 hours after PMSG treatment The serum LH levels showed a sharp increase at 60 hours after PMSG in control group, but there were no LH surge iii CC treatment group in spite of no significant difference in serum estradiol levels between two groups. While ovula tions occured in all rats in control group, there was no ovulation in CC treatment, group. However, with a single dose of hCG administration(10 IU. 54 hours after PMSG), ovulations occured in all rats in CC treatment group.
These results suggest that the certain serum levels of CC may :prevent the positive feedback effect of estradiol and suppress the LH surge, and this effect of CG may be reversed by the administration of hCG.
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