Evidence for a systemic embryotoxic effect of early luteal regression in the ewe

Evidence for a systemic embryotoxic effect of early luteal regression in the ewe. Beth A. Costine Experiments were performed to determine if a short-lived corpus luteum was embryotoxic in ewes given supplemental progesterone and the route of transfer of embryotoxic products. Mated ewes were lutectomized or sham lutectomized on day 4 after estrus. Following surgery, ewes received saline or PGF2α through days 6 or 7. Pregnancy rate was reduced after treatment with PGF2α (P < 0.001) compared to controls and was increased in PGF2α-treated ewes by lutectomy (P < 0.05). Mated ewes with bilateral ovulations were unilaterally lutectomized, and each uterine horn was ligated to eliminate intercornual flow on day 4 after estrus. Treatment with PGF2α on day 5 through 8 reduced pregnancy rates (P < 0.01), but embryonic survival did not differ in the uterine horns ipsilateral or contralateral to the regressing CL. The regressing CL is embryotoxic in progesterone-supplemented ewes, and embryotoxic luteal products have been shown to act by non-local pathways.