Effect of metritis on in-vitro uterine contractility in cows during the puerperium

Aim of this study was to determine the effect of metritis on in-vitro uterine contractility. Uteri obtained from 16 euthanized Holstein-Friesian cows were divided into two groups depending on whether metritis was absent (M-, n = 6) or present (M+, n = 10). Four longitudinal and four circular myometrial strips of all uteri were incubated in an organ bath. Spontaneous contractility was recorded in five consecutive 30-minute periods (T1-T5). This was followed by stimulation of one longitudinal and one circular strip with increasing concentrations of oxytocin, prostaglandinF_2α (PGF_2α), and calcium chloride (each during four 30-minute periods [T6-T9]). Strips in group M+ had higher minimum amplitude (minA) values at T1 and higher minA, mean amplitude (meanA), and area under the curve (AUC) values at T2 than strips in group M- (P ≤ 0.05). In the M+ group, the maximum amplitude (maxA), meanA, and AUC values of circular strips were higher than those of longitudinal strips during spontaneous contractility (T1, T4, and T5; P ≤ 0.05). The minA, meanA, and AUC values for strips in group M+ were higher than those in group M- when exposed to the highest concentration of PGF_2α (P ≤ 0.05). During stimulation with PGF_2α (T9), longitudinal strips had higher maxA values than the circular strips in group M+ (P ≤ 0.05). Spontaneous and stimulated contractility were temporarily increased in uteri with metritis compared to healthy uteri. Both myometrial layers, especially in uteri with metritis, reacted differently during spontaneous contractility and to stimulation with PGF_2α.