Endoh M, Maruyama M, Yanagisawa T
Life Sci. 1984 Dec 10;35(24):2397-406. doi: 10.1016/0024-3205(84)90447-8.
Cholera toxin (1-10 micrograms/ml) had a biphasic inotropic action on the isolated canine ventricular muscle: it produced a transient negative and a long lasting positive inotropic effect. The negative effect reached a maximum 43 +/- 2 min (n = 12) after administration of the toxin, while it took 3-5 hrs for the positive effect to reach a steady level. The positive inotropic effect of cholera toxin was accompanied by a prominent abbreviation of the time to peak tension and the relaxation time of individual contractions. The level of adenosine 3',5'-cyclic monophosphate (cyclic AMP) of the tissue was elevated by cholera toxin in a time- and concentration-dependent manner. Carbachol (1 mumol/l) administered 3 or 5 hrs after the administration of cholera toxin (10 micrograms/ml) reversed the increase in force of contraction and the elevation of cyclic AMP levels induced by cholera toxin. These results indicate that cholera toxin exerts a cyclic AMP-dependent positive inotropic effect and a negative inotropic effect which is not related to cyclic AMP levels in canine ventricular myocardium.
霍乱毒素（1 - 10微克/毫升）对离体犬心室肌有双相变力作用：它产生短暂的负性变力作用和持久的正性变力作用。负性作用在给予毒素后43±2分钟（n = 12）达到最大值，而正性作用达到稳定水平则需要3至5小时。霍乱毒素的正性变力作用伴随着单个收缩的张力峰值时间和舒张时间显著缩短。组织中3',5'-环磷酸腺苷（环磷酸腺苷）水平以时间和浓度依赖的方式被霍乱毒素升高。在给予霍乱毒素（10微克/毫升）3或5小时后给予卡巴胆碱（1微摩尔/升），可逆转霍乱毒素诱导的收缩力增加和环磷酸腺苷水平升高。这些结果表明，霍乱毒素在犬心室心肌中发挥依赖于环磷酸腺苷的正性变力作用以及与环磷酸腺苷水平无关的负性变力作用。
