Khan Firdous A, Chenier Tracey S, Murrant Coral L, Foster Robert A, Hewson Joanne, Scholtz Elizabeth L
Department of Population Medicine, University of Guelph, Canada.
Department of Population Medicine, University of Guelph, Canada.
Theriogenology. 2017 Mar 1;90:59-64. doi: 10.1016/j.theriogenology.2016.11.026. Epub 2016 Nov 28.
Nitric oxide (NO) may have a role in persistent breeding-induced endometritis in mares through an inhibitory effect on uterine contractility. The objectives of this study were to test the effect of NO on spontaneous uterine contractility in-vitro and to evaluate whether this effect varied between the longitudinal and circular muscle layers of the uterus. Reproductive tracts were collected from eight euthanized non-pregnant mares (age 4-19 years; body weight 405-530 kg). Transrectal examination of the reproductive tract was performed before euthanasia to evaluate stage of the estrous cycle and presence of any apparent abnormality. After euthanasia, one uterine tissue sample was collected for histological evaluation and four full-thickness uterine tissue strips (10-12 mm × 2 mm), two parallel to each muscle layer, were excised for in-vitro contractility evaluation. Strips were suspended in tissue chambers containing Krebs-Henseleit solution, with continuous aeration (95% O-5% CO; pH 7.4) at 37 °C. After equilibration, spontaneous contractility was recorded (pre-treatment) and strips excised in each direction were randomly allocated to each of two groups: 1) SNAP (S-nitroso-N-acetylpenicillamine, an NO donor); or 2) NAP (N-acetyl-d-penicillamine, vehicle and time-matched control). These were treated at 15 min intervals with increasing concentrations (10 M to 10 M) of SNAP and NAP, respectively. Contractility data was recorded throughout the experiment. An interaction effect of group-by-concentration was observed (P < 0.0001). The mean contractility after treatment with 10 M and 10 M SNAP were significantly lower than the pre-treatment contractility and the mean contractility after treatment with lower SNAP concentrations. In contrast, contractility did not change significantly in the NAP treated controls. The effect of treatment on uterine contractility was not influenced by age or weight of the mare, stage of estrous cycle, uterine histology grade, or muscle layer. Secondary findings included significant main effects of stage of estrous cycle (increased contractility in estrus compared to diestrus), uterine histology grade (decreased contractility in grade IIB compared to grade I) and age (decreased contractility in mares aged > 8 years compared to mares aged ≤ 8 years). In conclusion, results of this study indicate that NO has a dose-dependent inhibitory effect on spontaneous uterine contractility irrespective of the muscle layer in the mare.
一氧化氮（NO）可能通过对子宫收缩力的抑制作用，在母马持续性繁殖诱导的子宫内膜炎中发挥作用。本研究的目的是测试NO对体外子宫自发收缩力的影响，并评估这种影响在子宫纵肌层和环肌层之间是否存在差异。从八匹安乐死的未孕母马（年龄4 - 19岁；体重405 - 530千克）收集生殖道。在安乐死之前进行生殖道的经直肠检查，以评估发情周期阶段和是否存在任何明显异常。安乐死后，收集一份子宫组织样本用于组织学评估，并切取四条全层子宫组织条（10 - 12毫米×2毫米），其中两条与每个肌层平行，用于体外收缩力评估。将组织条悬挂在装有克-亨氏溶液的组织浴槽中，于37℃持续通气（95% O₂ - 5% CO₂；pH 7.4）。平衡后，记录自发收缩力（预处理），并将每个方向切取的组织条随机分配到两组中的每组：1）SNAP（S-亚硝基-N-乙酰青霉胺，一种NO供体）；或2）NAP（N-乙酰-D-青霉胺，载体及时间匹配对照）。分别以递增浓度（10⁻⁹M至10⁻⁵M）的SNAP和NAP每隔15分钟处理一次。在整个实验过程中记录收缩力数据。观察到组×浓度的交互作用（P < 0.0001）。用10⁻⁶M和10⁻⁵M SNAP处理后的平均收缩力显著低于预处理时的收缩力以及用较低SNAP浓度处理后的平均收缩力。相比之下，NAP处理的对照组中收缩力没有显著变化。治疗对子宫收缩力的影响不受母马的年龄、体重、发情周期阶段、子宫组织学分级或肌层的影响。次要发现包括发情周期阶段（发情期相比间情期收缩力增加）、子宫组织学分级（IIB级相比I级收缩力降低）和年龄（年龄>8岁的母马相比年龄≤8岁的母马收缩力降低）的显著主效应。总之，本研究结果表明，NO对母马子宫自发收缩力具有剂量依赖性抑制作用，且与肌层无关。
