Katoh H, Satoh H, Nakamura T, Terada H, Hayashi H
Third Department of Internal Medicine, Hamamatsu University School of Medicine, Japan.
Biochem Biophys Res Commun. 1994 Aug 30;203(1):93-8. doi: 10.1006/bbrc.1994.2153.
To investigate the mechanisms of Na+ loading during metabolic inhibition (MI), [Na+]i and pHi were measured in quiescent guinea pig myocytes using fluorescent probes, sodium-binding benzofuran isophthalate and 2,7,bis(carboxyethyl)-5,6-carboxyfluorescein. When myocytes were exposed to MI (3.3 mM amobarbital and 5 microM carbonyl cyanide m-chlorophenylhydrazone, without glucose) for 20 min, [Na+]i increased from 8.3 +/- 0.7 mM to 17.7 +/- 1.3 mM (p < 0.01) and pHi decreased from 7.22 +/- 0.03 to 7.00 +/- 0.04 (p < 0.05). The inhibition of Na(+)-H+ exchange by hexamethylene amiloride (HMA) significantly attenuated the increase in [Na+]i during MI (9.3 +/- 0.9 mM; p < 0.01 vs MI without HMA). When a K(+)-free solution was perfused to inhibit the Na+/K+ pump in the presence of HMA, there was an immediate increase in [Na+]i during MI. Perfusion of a K(+)-free solution after 10 min of MI caused no change in the rate of the increase in [Na+]i. We concluded that 1) Na+/H+ exchange was an important mechanism for Na+ elevation during MI, and 2) the Na+/K+ pump was functional during the early phase of MI, but was inhibited 10 min after MI in this model.
为研究代谢抑制（MI）期间钠负荷的机制，使用荧光探针、钠结合苯并呋喃异酞酸酯和2,7 - 双（羧乙基）- 5,6 - 羧基荧光素，在静止的豚鼠心肌细胞中测量细胞内钠浓度（[Na⁺]i）和细胞内pH值（pHi）。当心肌细胞暴露于MI（3.3 mM异戊巴比妥和5 μM羰基氰化物间氯苯腙，无葡萄糖）20分钟时，[Na⁺]i从8.3±0.7 mM增加到17.7±1.3 mM（p < 0.01），pHi从7.22±0.03降至7.00±0.04（p < 0.05）。六甲铵（HMA）抑制钠氢交换（Na⁺-H⁺交换）显著减弱了MI期间[Na⁺]i的增加（9.3±0.9 mM；与无HMA的MI相比，p < 0.01）。当在HMA存在下灌注无钾溶液以抑制钠钾泵时，MI期间[Na⁺]i立即增加。MI 10分钟后灌注无钾溶液，[Na⁺]i的增加速率无变化。我们得出结论：1）Na⁺-H⁺交换是MI期间钠升高的重要机制；2）在该模型中，钠钾泵在MI早期起作用，但在MI 10分钟后被抑制。
