Santostasi G, Kutty R K, Bartorelli A L, Yasumoto T, Krishna G
Section on Drug Tissue Interaction, National Heart, Lung and Blood Institute, Bethesda, Maryland.
Toxicol Appl Pharmacol. 1990 Jan;102(1):164-73. doi: 10.1016/0041-008x(90)90093-a.
Maitotoxin, the most potent marine toxin, is known to increase the uptake and the accumulation of Ca2+ into cells, and was used in the present study to investigate the mechanisms of myocardial cell damage induced by Ca2+ overload. In cultured cardiomyocytes, isolated from 2-day-old rats, maitotoxin affected cell viability, as indicated by the leakage of the cytosolic enzyme lactate dehydrogenase (LDH) and of radiolabeled adenine nucleotides into the extracellular medium. Maitotoxin-induced leakage of LDH steadily increased between 30 min and 24 hr, and was preceded by a marked depletion of intracellular ATP. Addition of maitotoxin resulted in a rapid influx of extracellular Ca2+, as detected by preincubating the cells in the presence of 45Ca; this effect evolved in a few minutes, thus preceding the signs of cell death. Cytosolic levels of free Ca2+ ([Ca2+]i) were monitored by loading freshly isolated, suspended cardiomyocytes with the intracellular fluorescent probe fura-2; in these cells, maitotoxin induced a dose-dependent increase in [Ca2+]i, with a lag phase of less than a minute. All these effects of maitotoxin were inhibited by reducing Ca2+ concentration in the culture medium or by incubating the cells with the calcium-channel blocking drug verapamil. It is thus demonstrated that maitotoxin-induced cardiotoxicity is secondary to an inordinate influx of Ca2+ into the cells. It is also suggested that, in those conditions that lead to an inordinate accumulation of Ca2+ into myocardial cells, the unmatched demands of energy and the depletion of ATP play a primary role in the irreversible stage of cell damage.
刺尾鱼毒素是毒性最强的海洋毒素，已知它会增加细胞对钙离子的摄取和积累，在本研究中被用于探究钙离子过载诱导心肌细胞损伤的机制。在从2日龄大鼠分离培养的心肌细胞中，刺尾鱼毒素影响细胞活力，这表现为胞质酶乳酸脱氢酶（LDH）和放射性标记的腺嘌呤核苷酸泄漏到细胞外培养基中。刺尾鱼毒素诱导的LDH泄漏在30分钟至24小时之间稳步增加，且在此之前细胞内ATP显著耗竭。加入刺尾鱼毒素导致细胞外钙离子迅速内流，这是通过在45Ca存在下预孵育细胞检测到的；这种效应在几分钟内就出现了，因此早于细胞死亡的迹象。通过用细胞内荧光探针fura-2加载新鲜分离的悬浮心肌细胞来监测游离钙离子（[Ca2+]i）的胞质水平；在这些细胞中，刺尾鱼毒素诱导[Ca2+]i呈剂量依赖性增加，滞后阶段不到一分钟。刺尾鱼毒素的所有这些效应都可通过降低培养基中的钙离子浓度或用钙通道阻滞剂维拉帕米孵育细胞来抑制。因此证明，刺尾鱼毒素诱导的心脏毒性是细胞内钙离子过度内流的继发结果。还表明，在导致钙离子在心肌细胞中过度积累的情况下，能量需求不匹配和ATP耗竭在细胞损伤的不可逆阶段起主要作用。
