An in vitro study on spontaneous myometrial contractility in the cow during estrus and diestrus.

Myometrial smooth muscle strips were collected from slaughtered cows in estrus and diestrus. Longitudinal and circular smooth muscle strips were mounted in organ baths and after equilibration time and 2g preload, their physiologic contractility was recorded for 3h. Area under the curve (AUC), mean amplitude (MA) and frequency of contractions (F) were studied. Differences between cycle phases, between muscle layers and over the recorded time period were statistically evaluated. In the cow, physiologic contractility patterns (measured as AUC and MA) of circular versus longitudinal myometrial strips are always different during the 3h recording. Significant differences between estrus versus diestrus are only found for circular layers, but not for longitudinal layers. Significant differences over time are only found for longitudinal layers.