Local Effect of an Intrauterine Plastic Coil on the Corpus Luteum of the Ewe

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Abstract
A polyethylene plastic coil (pre-insertion diameter = 15 mm, length = 20 mm) was inserted surgically into the cranial portion of one uterine horn of each of 26 mature ewes. The insertions were made on day 4 of the estrous cycle (estrus - day 1). On day 6, after the 1st or 2nd postoperative estrus, the ewes were autopsied. The average weight (mg) of corpora lutea (CL) when on the operative side and nonoperative side, respectively, for the following CL locations and ewe numbers (in parentheses) were: 1 CL in 1 ovary = 206.7 (6) and 333.8 (5); 2 CL in 1 ovary = 146.9 (5) and 280.2 (2); 1 CL in each ovary (6) = 155.8 and 233.0; 3 CL, 1 or 2 in each ovary (2) = 138.0 and 231.2. The CL on the operative side were smaller (P<.01 for both the unilaterally and bilaterally ovulating groups). The observed length of the operative estrous cycle, when the relationship of coil location to side of ovulation was known, was shorter (P<.05) for the 7 ewes which had ovulated on only the operative side (average, 12.0 days) than for the 11 ewes which had ovulated on only the nonoperative side (average, 17.8). These data indicate that a plastic coil inserted in 1 uterine horn of the ewe results in a unilateral inhibitory influence on the CL.