Lelievr L G, Crambert G, Allen P D
Laboratoire de Pharmacologie des Transports Ioniques Membranaires, EA 2381, Université Paris 7, France.
Cell Mol Biol (Noisy-le-grand). 2001 Mar;47(2):265-71.
In human heart failure, disturbances in Ca2+ homeostasis are well known but the fate of the Na,K-ATPase isoforms (alpha1beta1, alpha2beta1 and alpha3beta1), the receptors for cardiac glycosides, still remains under study. Microsomes have been purified from non-failing human hearts. As judged by the sensitivities of Na,K-ATPase activity to ouabain (IC50 values: 7.0 +/- 2.5 and 81 +/- 11 nM), 3H-ouabain-binding measurements at equilibrium with and without 10 mM K+ and by a biphasic ouabain dissociation process, at least two finctionally active Na,K-ATPase isozymes coexist in normal human hearts. These are demonstrated as a very high- and a high affinity ouabain-binding site. The KD values are 3.6 +/- 1.6 nM and 17 +/- 6 nM, respectively. The two dissociation rate constants are 42 x 10(4) min(-1) and 360 x 10(-4) min(-1). Addition of 10 mM K+ ions shifted the respective KD values for ouabain from 3.6 +/- 1.6 to 20 +/- 5 nM and from 17 +/- 6 nM to 125 +/- 25 nM, respectively. The isozymes involved are identified by comparing these three pharmacological parameters to those of each alpha/beta-isozyme separately expressed in Xenopus oocytes (9). In human heart, the very high affinity site for ouabain is the alpha1beta1 dimer and the high affinity site is alpha2beta1.
在人类心力衰竭中，钙稳态紊乱是众所周知的，但钠钾ATP酶同工型（α1β1、α2β1和α3β1），即强心苷的受体，其命运仍在研究中。已从正常人类心脏中纯化出微粒体。根据钠钾ATP酶活性对哇巴因的敏感性（IC50值：7.0±2.5和81±11 nM）、在有和没有10 mM钾离子存在下平衡时的3H-哇巴因结合测量以及哇巴因的双相解离过程判断，正常人类心脏中至少共存两种功能活性钠钾ATP酶同工酶。这些表现为一个非常高亲和力和一个高亲和力的哇巴因结合位点。KD值分别为3.6±1.6 nM和17±6 nM。两个解离速率常数分别为42×10⁴ min⁻¹和360×10⁻⁴ min⁻¹。加入10 mM钾离子后，哇巴因各自的KD值分别从3.6±1.6 nM变为20±5 nM，从17±6 nM变为125±25 nM。通过将这三个药理学参数分别与在非洲爪蟾卵母细胞中单独表达的每种α/β同工型的参数进行比较，确定了所涉及的同工酶（9）。在人类心脏中，哇巴因的非常高亲和力位点是α1β1二聚体，高亲和力位点是α2β1。
