Morita K, Koketsu K
Jpn J Physiol. 1979;29(3):239-50. doi: 10.2170/jjphysiol.29.239.
The effect of adrenaline (Ad) on the electrogenic Na+ pump of bullfrog visceral nerve fibers was studied, by testing the effect of this drug on the K-activated hyperpolarization (KAH) of these nerve fibers. KAHs were recorded by adding K (0.2--5 mM) to an extracellular K-free solution with which preparations were previously perfused and the actual KAH amplitude (net KAH) was estimated by taking into account the amplitude of membrane depolarization induced by K in the presence of ouabain (0.001 mM). The dose-response relation between K concentrations and net KAHs follows Michaelis-Menten kinetics; the log dose-response relation showed a sigmoid curve and the Lineweaver-Burk Plot of dose-response relation showed a straight line when nH=1.3. The net KAH was augmeted by Ad (0.03--1 mM); facilitative effects of three kinds of catecholamine on the net KAH were Ad greater than noradrenaline greater than isopreterenol. The log dose-response curve was shifted to the left in parallel in the presence of Ad; the Lineweeather-Burk plot showed a straight line when nH=1.3 and this line met the control line at the ordinate point where K concentration is infinitive, while the apparent dissociation constant (Km) decreased to 0.82 from 1.3 mM (control) in the presence of 0.3 mM Ad. Net KAH was augmented by the removal of extracellular Cl or by the action of TEA; the membrane resistance was expected to increase under these experimental conditions. The dose-response relation obtained under these conditions showed an increase of maximum response without changes in Km value. It was concluded on the basis of the present results that the increase in net KAH by Ad was due to an increase in the electrogenic Na+ pump current. The mechanism underlying such an Ad action was discussed, and it was suggested that the rate of the electrogenic Na+ pump was increased by the action of Ad.
通过测试肾上腺素（Ad）对牛蛙内脏神经纤维钾激活超极化（KAH）的影响，研究了其对牛蛙内脏神经纤维电生性钠泵的作用。通过向先前灌注过的细胞外无钾溶液中添加钾（0.2 - 5 mM）来记录KAH，并通过考虑在哇巴因（0.001 mM）存在下钾诱导的膜去极化幅度来估计实际的KAH幅度（净KAH）。钾浓度与净KAH之间的剂量 - 反应关系遵循米氏动力学；对数剂量 - 反应关系呈S形曲线，当nH = 1.3时，剂量 - 反应关系的Lineweaver - Burk图呈直线。Ad（0.03 - 1 mM）可增强净KAH；三种儿茶酚胺对净KAH的促进作用为Ad＞去甲肾上腺素＞异丙肾上腺素。在Ad存在下，对数剂量 - 反应曲线平行向左移动；当nH = 1.3时，Lineweeather - Burk图呈直线，且该线在钾浓度为无穷大的纵坐标点与对照线相交，而在0.3 mM Ad存在下，表观解离常数（Km）从1.3 mM（对照）降至0.82 mM。去除细胞外氯离子或TEA的作用可增强净KAH；在这些实验条件下，预计膜电阻会增加。在这些条件下获得的剂量 - 反应关系显示最大反应增加而Km值不变。根据目前的结果得出结论，Ad导致净KAH增加是由于电生性钠泵电流增加。讨论了这种Ad作用的潜在机制，并提出Ad的作用增加了电生性钠泵的速率。
