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. 1972 Nov;35(5):1001-4.
doi: 10.2527/jas1972.3551001x.

Inhibition by progesterone of IUD-induced luteal regression in the ewe

Inhibition by progesterone of IUD-induced luteal regression in the ewe

J E Warren Jr et al. J Anim Sci. 1972 Nov.

Abstract

PIP: A U.S. Department of Agriculture study at Beltsville, Maryland investigated the effect of progesterone on IUD-induced luteal regression in 95 ewes. The IUD was a plastic spiral with diameter 9 mm and length 30 mm. The first experiment suggested that IUD-induced regression of a corpus luteum (CL) is dependent upon the stage of the estrous cycle but unrelated to the age of the CL. When ovulation was induced on Cycle Day 5 in 4 ewes and an IUD was inserted on Day 7, neither the original CLs, about 6 days old, nor the induced CLs, about 1 day old, regressed. Experiment 2 provided evidence that exogenous progesterone generally prevents IUD-induced luteal regression. 29 ewes were injected twice daily on Days 1-4 of a cycle with 10 mg of progesterone in corn oil or with corn oil alone. An IUD was inserted on Day 3. Sacrifice was on Day 9. Early CL (ovaries ipsilateral to IUD) regression occurred in 7 in the corn-oil group but in only 2 in the progesterone group. In Experiment 3 the administration of progesterone to estradiol- and IUD-treated ewes tended to reduce the percentage of ewes with regressed CL's (p=.10, ovaries ipsilateral to IUD). Estradiol itself extends the stage during which the insertion of an IUD causes luteolysis.

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