Posner P, Farrar E L, Lambert C R
Am J Physiol. 1976 Nov;231(5 Pt. 1):1415-20. doi: 10.1152/ajplegacy.1976.231.5.1415.
The effect of catecholamines over a wide range of concentrations was studied on 42K uptake and efflux, as well as on spontaneous rate in canine cardiac Purkinje fibers. Low levels of catecholamines (less than 10(-10) M epinephrine; less than 10(-9) M norepinephrine) decreased automaticity. This negative chronotropic effect was blocked by phentolamine and mimicked by phenylephrine. These low levels of epinephrine and norepinephrine also inhibited 42K uptake by Purkinje fibers but had no effect on 42K efflux. The inhibition of 42K uptake was blocked by phentolamine and verapamil and mimicked by phenylephrine. The data indicate an alpha-receptor-mediated negative response of rate and 42K uptake to low levels of catecholamine. The end result is discussed in terms of a competitive increase in the influx of Ca2+ rather than Na+ and an indirect inhibition of the Na+-K+ pump.
研究了不同浓度儿茶酚胺对犬心脏浦肯野纤维42K摄取、流出以及自发速率的影响。低水平儿茶酚胺（肾上腺素浓度低于10(-10) M；去甲肾上腺素浓度低于10(-9) M）可降低自律性。这种负性变时作用可被酚妥拉明阻断，而被去氧肾上腺素模拟。这些低水平的肾上腺素和去甲肾上腺素还抑制浦肯野纤维对42K的摄取，但对42K流出无影响。42K摄取的抑制作用可被酚妥拉明和维拉帕米阻断，而去氧肾上腺素可模拟此作用。数据表明，低水平儿茶酚胺对速率和42K摄取的负性反应是由α受体介导的。最终结果从Ca2+而非Na+内流的竞争性增加以及对Na+-K+泵的间接抑制方面进行了讨论。
