Snape W J, Yoo S
J Pharmacol Exp Ther. 1985 Dec;235(3):690-5.
The purpose of these studies was to evaluate the direct effect of amino acids on rabbit colonic smooth muscle. Isometric tension was measured in circular smooth muscle from the distal colon after the administration of 19 individual L-amino acids. L-Alanine, L-cysteine, L-serine and L-methionine stimulated a dose-dependent increase in isometric tension. The lowest concentration which increased tension of the tissue for each of these amino acids was between 1 X 10(-4) to 5 X 10(-4) M. At a concentration of 10(-3) M, each of these four amino acids stimulated smooth muscle to 40 to 60% of the maximum response to bethanechol (2050 +/- 105 mN/m2). The 15 other amino acids tested had less effect on the colonic smooth muscle. The smooth muscle response to the D-amino acids, D-alanine, D-cysteine or D-serine, was shifted 10-fold to the right. Neural blockade by tetrodotoxin, the alpha adrenergic receptor antagonist, phentolamine, or the alpha-2 antagonist, yohimbine, increased smooth muscle tension, but did not inhibit L-amino acid stimulation of the tissue. Atropine, naloxone or prazosin (alpha-1 adrenergic antagonist) had no effect on amino acid stimulation of the muscle. These data suggest that L-amino acids, alanine, serine, cysteine and methionine stimulate contraction of colonic circular smooth muscle, this response is stereospecific and amino acids appear to stimulate the smooth muscle directly and not through an effect on the myenteric neurons.
这些研究的目的是评估氨基酸对兔结肠平滑肌的直接作用。在给予19种单个L-氨基酸后，测量远端结肠环形平滑肌的等长张力。L-丙氨酸、L-半胱氨酸、L-丝氨酸和L-甲硫氨酸刺激等长张力呈剂量依赖性增加。这些氨基酸中每种使组织张力增加的最低浓度在1×10⁻⁴至5×10⁻⁴M之间。在10⁻³M的浓度下，这四种氨基酸中的每一种都能将平滑肌刺激至对氨甲酰甲胆碱最大反应（2050±105mN/m²）的40%至60%。所测试的其他15种氨基酸对结肠平滑肌的作用较小。平滑肌对D-氨基酸、D-丙氨酸、D-半胱氨酸或D-丝氨酸的反应向右偏移了10倍。河豚毒素、α肾上腺素能受体拮抗剂酚妥拉明或α-2拮抗剂育亨宾引起的神经阻滞增加了平滑肌张力，但并未抑制L-氨基酸对组织的刺激。阿托品、纳洛酮或哌唑嗪（α-1肾上腺素能拮抗剂）对氨基酸对肌肉的刺激没有影响。这些数据表明，L-氨基酸、丙氨酸、丝氨酸、半胱氨酸和甲硫氨酸可刺激结肠环形平滑肌收缩，这种反应具有立体特异性，并且氨基酸似乎是直接刺激平滑肌，而非通过对肠肌神经元的作用来实现。
