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Relationship of Endocrine State to Spontaneous Motility of Sheep Myometrium in vitro

United States Department of Agriculture, Beltsville, Maryland^,2

Abstract

Spontaneous motility of myometrial strips incubated in vitro was studied during the estrous cycle and following ovariectomy. The amplitude of contraction, frequency of contraction and an activity index (amplitude x frequency) were used to assess uterine motility. Among estrous, luteal phase and ovariectomizedewes, amplitude, frequency and activity index were each greatest in estrous ewes and lowest in luteal-phase ewes. Estradiol injected into ovariectomized ewes increased the frequency but not the amplitude of contraction, while progesterone injected into ovariectomizedewes decreased both frequency and amplitude of contraction. Acetylcholine or oxytocin caused sustained contraction of myometrium of ewes from all endocrine groups. Epinephrine had effects similar to acetylcholineor oxytocin in estrous and luteal phase ewes, but stopped activity in ovariectomized ewes.

¹ The author expresses appreciation to H. W. Hawk for advice in preparation of this manuscript, to F. Stormshak for supplying some of the uterine tissue used in this study and to D. Higginbotham for technical assistance.

² Animal Husbandry Research Division.