Lelievre L G, Mansier P, Charlemagne D, Swynghedauw B
Basic Res Cardiol. 1984;79 Suppl:128-33. doi: 10.1007/978-3-642-72376-6_17.
The sensitivity of the Na+, K+-ATPase to ouabain has been studied in sarcolemma vesicles isolated from normal rat heart. Two enzyme forms exhibiting high and low sensitivities to ouabain have been observed in Ca2+-free perfused heart. The half-maximal inhibitory effects occurred with 1-2 X 10(-8) M ouabain. The high sensitivity form undetectable in hearts maintained at a physiological Ca2+ level might represent altered low affinity sites or latent enzyme forms unmasked by low calcium concentrations. The heterogeneity of the Na+, K+-ATPase forms was found to be also modulated by the K+/ouabain antagonism, addition of K+ accentuating the heterogeneity. These in vitro results associated with in vivo experiments on isolated rat heart working under isovolumic conditions suggested that lowering Ca2+ has qualitative and quantitative effects. Low Ca2+ concentrations increased the sensitivities to ouabain and the amplitudes of both the enzyme inhibition and the positive inotropic effects.
已在从正常大鼠心脏分离的肌膜囊泡中研究了钠钾ATP酶对哇巴因的敏感性。在无钙灌注心脏中观察到两种对哇巴因表现出高敏感性和低敏感性的酶形式。半最大抑制效应在1-2×10（-8）M哇巴因时出现。在生理钙水平维持的心脏中无法检测到的高敏感性形式可能代表改变的低亲和力位点或被低钙浓度暴露的潜在酶形式。发现钠钾ATP酶形式的异质性也受到钾/哇巴因拮抗作用的调节，添加钾会加剧异质性。这些体外结果与在等容条件下工作的离体大鼠心脏的体内实验相关，表明降低钙具有定性和定量作用。低钙浓度增加了对哇巴因的敏感性以及酶抑制和正性肌力作用的幅度。
