Mann D L, Kent R L, Parsons B, Cooper G
Department of Medicine, Gazes Cardiac Research Institute, Medical University of South Carolina, Charleston.
Circulation. 1992 Feb;85(2):790-804. doi: 10.1161/01.cir.85.2.790.
To delineate the mechanism(s) of catecholamine-mediated cardiac toxicity, we exposed cultures of adult cardiac muscle cells, or cardiocytes, to a broad range of norepinephrine concentrations.
Norepinephrine stimulation resulted in a concentration-dependent decrease in cardiocyte viability, as demonstrated by a significant decrease in viable rod-shaped cells and a significant release of creatine kinase from cells in norepinephrine-treated cultures. Norepinephrine-mediated cell toxicity was attenuated significantly by beta-adrenoceptor blockade and mimicked by selective stimulation of the beta-adrenoceptor, whereas the effects mediated by the alpha-adrenoceptor were relatively less apparent. When norepinephrine stimulation was examined in terms of cardiocyte anabolic activity, there was a concentration-dependent decrease in the incorporation of [3H]phenylalanine and [3H]uridine into cytoplasmic protein and nuclear RNA, respectively. The decrease in cytoplasmic labeling was largely attenuated by beta-adrenoceptor blockade and mimicked by selective stimulation of the beta-adrenoceptor, but alpha-adrenoceptor stimulation resulted in relatively minor decreases in cytoplasmic labeling. The norepinephrine-induced toxic effect appeared to be the result of cyclic AMP-mediated calcium overload of the cell, as suggested by studies in which pharmacological strategies that increased intracellular cyclic AMP led to decreased cell viability, as well as studies that showed that influx of extracellular calcium through the verapamil-sensitive calcium channel was necessary for the induction of cell lethality. Additional time-course studies showed that norepinephrine caused a rapid, fourfold increase in intracellular cyclic AMP, followed by a 3.2-fold increase in intracellular calcium [( Ca2+]i).
These results constitute the initial demonstration at the cellular level that adrenergic stimulation leads to cyclic AMP-mediated calcium overload of the cell, with a resultant decrease in synthetic activity and/or viability.
为了阐明儿茶酚胺介导的心脏毒性机制，我们将成年心肌细胞（即心肌细胞）培养物暴露于广泛的去甲肾上腺素浓度范围内。
去甲肾上腺素刺激导致心肌细胞活力呈浓度依赖性下降，这表现为在去甲肾上腺素处理的培养物中，存活的杆状细胞显著减少，且细胞中肌酸激酶大量释放。β-肾上腺素能受体阻断可显著减轻去甲肾上腺素介导的细胞毒性，而选择性刺激β-肾上腺素能受体则可模拟这种毒性，而α-肾上腺素能受体介导的效应相对不明显。当从心肌细胞合成代谢活性方面检测去甲肾上腺素刺激时，[3H]苯丙氨酸和[3H]尿苷分别掺入细胞质蛋白和核RNA的量呈浓度依赖性下降。细胞质标记的减少在很大程度上被β-肾上腺素能受体阻断所减弱，且可被β-肾上腺素能受体的选择性刺激所模拟，但α-肾上腺素能受体刺激导致细胞质标记相对较小程度的减少。去甲肾上腺素诱导的毒性作用似乎是细胞内环状AMP介导的钙超载的结果，这一观点得到了以下研究的支持：增加细胞内环状AMP的药理学策略导致细胞活力下降的研究，以及表明通过维拉帕米敏感钙通道的细胞外钙内流是诱导细胞死亡所必需的研究。额外的时间进程研究表明，去甲肾上腺素使细胞内环状AMP迅速增加四倍，随后细胞内钙（[Ca2+]i）增加3.2倍。
这些结果在细胞水平上首次证明，肾上腺素能刺激导致细胞内环状AMP介导的钙超载，进而导致合成活性和/或活力下降。
