Spontaneous myometrial contractility in cows suffering from endometritis—Influence of localisation, smooth muscle layer and cycle phase. An in vitro study

Contractility of the healthy bovine myometrium depends on the reproductive state. Furthermore, contractility is influenced by localisation and the direction of smooth muscle strips. However, little is known about the contractile behaviour of the uterus when affected by endometritis. In our study, myometrial specimens from the larger horn (near the corpus and near the tip) in cows suffering from endometritis in estrus (n = 8) or diestrus (n = 8) were collected after slaughter. Two strips were prepared from each region corresponding to the circular and the longitudinal muscle layers, respectively. The spontaneous contractility of these strips was recorded in an organ bath. To analyse the results, the 2.5 h recordings were divided into five periods of 30 min each. The variables area under curve (AUC) and maximal (Amax) and minimal amplitude (Amin) were calculated separately for each period, and the results were analysed using a non-parametric model regarding the influence of cycle phase (estrus vs. diestrus), region (corpus vs. tip) and muscle layer (circular vs. longitudinal). The values of both AUC and Amax increased significantly over time. Muscle layer had a significant effect on AUC (corpus, tip) and Amax (tip): the values of circular layers were increased compared to longitudinal layers. Dividing the data into subgroups allowed us to analyse them additionally according to muscle layer: In longitudinal layers, Amax was increased at the corpus as compared with the tip. In this model, the factor cycle phase did not produce any significant difference in spontaneous myometrial activity. However, data of all variables showed non-significant higher values in estrus than in diestrus samples.