The influence of the female sex hormones on the response of the pig uterus to electrical stimulation

Abstract

The response of the pig myometrium to electrical stimulation in vitro was used to assess the influence of the female sex hormones at different stages of the oestrus cycle. Optimal stimulation produced greater tension in the mature uterus than in the immature uterus and the tension was greater in the oestrogen-dominated uterus than in the progesterone-dominated uterus. The minimum (threshold) voltage necessary to elicit an isometric contraction was not influenced by the stage of the uterus in the oestrus cycle. Varying the frequency of stimulation caused changes in tension indicating the predominant sex hormone. The progesterone-dominated myometrium appears to bind calcium more strongly than the oestrogen-dominated myometrium.