Yokoyama S, Ohhashi T
First Department of Physiology, Shinshu University School of Medicine, Matsumoto, Japan.
Am J Physiol. 1993 May;264(5 Pt 2):H1460-4. doi: 10.1152/ajpheart.1993.264.5.H1460.
The effects of acetylcholine (ACh) on spontaneous contractions in isolated bovine mesenteric lymph vessels were investigated. ACh ranging from 3 x 10(-8) M to 10(-5) M produced dose-dependent negative chronotropic and inotropic effects on the spontaneous contractions. In the lymph vessels without endothelium, ACh at the same concentration range had no significant effect on the spontaneous contractions. Atropine (10(-9) and 10(-8) M) caused a parallel shift to the right of the dose-chronotropic response curve for ACh. The pA2 value of atropine to ACh in the negative chronotropic effect was 8.90 +/- 0.20 (n = 6). Aspirin (10(-5) M) produced no significant inhibition of the ACh-induced negative chronotropic and inotropic effects. NG-monomethyl-L-arginine (L-NMMA; 3 x 10(-5) M) significantly suppressed the ACh-induced negative responses on spontaneous contractions. In the same lymphatic segments, L-arginine (10(-4) M) reversed completely the inhibition by L-NMMA of the ACh-induced responses. These results suggest that low concentrations of ACh produce negative chronotropic and inotropic effects on spontaneous contractions in bovine mesenteric lymphatics and that the responses may be mediated by nitric oxide or its related compound released from the endothelial cells through activation of low-affinity muscarinic receptors.
研究了乙酰胆碱（ACh）对离体牛肠系膜淋巴管自发收缩的影响。浓度范围为3×10⁻⁸M至10⁻⁵M的ACh对自发收缩产生剂量依赖性的负性变时性和变力性作用。在无内皮的淋巴管中，相同浓度范围的ACh对自发收缩无显著影响。阿托品（10⁻⁹和10⁻⁸M）使ACh的剂量-变时反应曲线平行右移。阿托品对ACh负性变时作用的pA2值为8.90±0.20（n = 6）。阿司匹林（10⁻⁵M）对ACh诱导的负性变时性和变力性作用无显著抑制作用。N⁻单甲基-L-精氨酸（L-NMMA；3×10⁻⁵M）显著抑制ACh对自发收缩诱导的负性反应。在相同的淋巴管段中，L-精氨酸（10⁻⁴M）完全逆转了L-NMMA对ACh诱导反应的抑制作用。这些结果表明，低浓度的ACh对牛肠系膜淋巴管的自发收缩产生负性变时性和变力性作用，且这些反应可能由内皮细胞通过低亲和力毒蕈碱受体激活释放的一氧化氮或其相关化合物介导。
