Cunarro J A, Weiner M W
J Pharmacol Exp Ther. 1978 Jul;206(1):198-206.
In order to investigate the mechanism of action of ethacrynic acid and furosemide, experiments were designed to determine whether these drugs directly inhibit active transport or energy metabolism. The effects of these diuretics on the respiration of tubule suspensions isolated from renal cortex (of rats and rabbits) and outer medulla (of rabbits) were measured. The respiration of tubules prepared from renal outer medulla was stimulated by the presence of chloride in the incubation medium, whereas the respiration of cortical tubules was unaffected by chloride. Both ethacrynic acid and furosemide produced the greatest inhibition of respiration on tubules from outer medulla suspended in chloride-containing media; this result suggests that the diuretics directly inhibit chloride transport. The source of metabolic energy for ion transport was varied by using substrates which donate electrons to the respiratory chain at different phosphorylation sites. Both ethacrynic acid and furosemide inhibit respiration supported by beta-hydroxybutyrate, but there was little or no inhibition of respiration with succinate or tetramethylphenylenediamine ascorbate. Similarly, ouabain inhibited respiration with beta-hydroxybutyrate, but not with the other substrates. Therefore, both diuretics inhibited respiration in a fashion similar to ouabain. It is concluded from both types of experiments that ethacrynic acid and furosemide may directly inhibit active chloride transport.
为了研究依他尼酸和呋塞米的作用机制，设计了实验来确定这些药物是否直接抑制主动转运或能量代谢。测定了这些利尿剂对从（大鼠和兔子的）肾皮质以及（兔子的）外髓质分离出的肾小管悬浮液呼吸的影响。在孵育培养基中存在氯离子时，由肾外髓质制备的肾小管的呼吸受到刺激，而皮质肾小管的呼吸不受氯离子影响。依他尼酸和呋塞米对悬浮于含氯培养基中的外髓质肾小管的呼吸抑制作用最强；这一结果表明利尿剂直接抑制氯离子转运。通过使用在不同磷酸化位点向呼吸链供电子的底物来改变离子转运的代谢能量来源。依他尼酸和呋塞米均抑制由β-羟基丁酸支持的呼吸，但对由琥珀酸盐或抗坏血酸四甲基苯二胺支持的呼吸几乎没有抑制作用。同样，哇巴因抑制由β-羟基丁酸支持的呼吸，但不抑制由其他底物支持的呼吸。因此，这两种利尿剂均以类似于哇巴因的方式抑制呼吸。从这两类实验得出的结论是，依他尼酸和呋塞米可能直接抑制主动氯离子转运。
