Ishida H, Kohmoto O, Bridge J H, Barry W H
Department of Medicine, University of Utah School of Medicine, Salt Lake City 84132.
J Clin Invest. 1988 Apr;81(4):1173-81. doi: 10.1172/JCI113432.
Alterations in cation homeostasis during and after recovery from myocardial ischemia may account for some of the reversible and irreversible components of myocardial cell injury. To investigate possible mechanisms involved, we exposed cultured layers of spontaneously contracting chick embryo ventricular cells to media containing 1 mM cyanide (CN) and 20 mM 2-deoxyglucose (2-DG), and zero glucose for up to 6 h, and then allowed cultured cells to recover in serum-free culture medium for 24 h. Changes in Na, K, and Ca contents, 42K uptake and efflux, ATP content, cell water content, and lactate dehydrogenase (LDH) release were measured, and compared with changes produced by exposure to 10(-3) M ouabain and severe hypoxia. Exposure to CN and 2-DG caused marked increase in cell Na (sevenfold) and Ca (fivefold) contents, and a decrease in K content (one-fifth normal), coincident with ATP depletion to one-tenth normal levels. This produced only slight cell injury, evidenced by increased LDH release. Recovery for 24 h resulted in return to near normal values (expressed in nanomoles per milligram of protein) of Na, Ca, and ATP contents. However, there was failure of cell K content to return to normal, associated with a persistent reduced net uptake of 42K, and an increase in the rate of 42K efflux. These abnormalities in K homeostasis were associated with a decrease in cell volume and water content per milligram of protein. More marked ATP depletion (to 1/100 normal values) was produced by hypoxia plus 2-DG and zero glucose, and was associated with much more severe cell injury manifested by LDH loss. Ouabain exposure resulted in a much greater Ca gain (20-30-fold), relative to increase in Na content, than did either CN and 2-DG or hypoxia; and ouabain effects were not reversible (after a 15-fold or greater increase in Ca content was produced) and were associated with significant LDH release. We conclude that these cells are resistant to cell injury caused by moderately severe Ca overload and ATP depletion produced by exposure to CN and 2-DG. However, metabolic inhibition of ATP production produces persistent abnormalities in K homeostasis, associated with functional abnormalities.
心肌缺血期间及恢复后阳离子稳态的改变可能是心肌细胞损伤的一些可逆和不可逆成分的原因。为了研究其中可能涉及的机制，我们将自发收缩的鸡胚心室细胞培养层暴露于含有1 mM氰化物（CN）和20 mM 2-脱氧葡萄糖（2-DG）且葡萄糖为零的培养基中长达6小时，然后让培养的细胞在无血清培养基中恢复24小时。测量了钠、钾和钙含量、42K摄取和流出、ATP含量、细胞含水量以及乳酸脱氢酶（LDH）释放的变化，并与暴露于10(-3) M哇巴因和严重缺氧所产生的变化进行了比较。暴露于CN和2-DG导致细胞钠含量（增加7倍）和钙含量（增加5倍）显著增加，钾含量降低（降至正常的五分之一），同时ATP耗竭至正常水平的十分之一。这仅产生了轻微的细胞损伤，表现为LDH释放增加。恢复24小时导致钠、钙和ATP含量恢复到接近正常值（以每毫克蛋白质的纳摩尔数表示）。然而，细胞钾含量未能恢复正常，伴有42K净摄取持续减少以及42K流出速率增加。钾稳态的这些异常与每毫克蛋白质的细胞体积和含水量减少有关。缺氧加2-DG和零葡萄糖导致更明显的ATP耗竭（降至正常水平的1/100），并伴有以LDH损失为表现的更严重的细胞损伤。与CN和2-DG或缺氧相比，哇巴因暴露导致相对于钠含量增加而言钙摄取增加得更多（增加20 - 30倍）；哇巴因的作用是不可逆的（在钙含量增加15倍或更多后），并伴有显著的LDH释放。我们得出结论，这些细胞对由暴露于CN和2-DG所产生的中度严重钙超载和ATP耗竭引起的细胞损伤具有抗性。然而，ATP生成的代谢抑制会导致钾稳态持续异常，并伴有功能异常。
