Na+,K+-ATPase Na+ Affinity in Rat Skeletal Muscle Fiber Types
Na+,K+-ATPase Na+ Affinity in Rat Skeletal Muscle Fiber Types
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DOI：
10.1007/s00232-010-9237-6
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发表时间：
2010-03-01
影响因子：
2.4
通讯作者：
Juel, Carsten
中科院分区：
文献类型：
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作者：
Kristensen, Michael;Juel, Carsten
先前对表达系统的研究发现Na+/K+- atp酶同工酶的离子激活不同，这表明不同肌肉具有不同的离子亲和性。采用ATP水解速率定量测定Na+、K+-ATP酶活性，并研究Na+、K+-ATP酶在大鼠肌肉总膜和不同纤维类型肌肉纯化膜中的Na+亲和力。氧化肌与糖酵解肌相比Na+亲和力更高（K (m)更低），氧化肌纯化膜与糖酵解肌相比Na+亲和力更低。Na+，K+- atp酶异构体分析表明，含有β(1)异构体的异源二聚体比含有β(2)异构体的异源二聚体具有更高的Na+亲和力。免疫沉淀实验表明，具有α(1)的二聚体约占Na， k - atp酶总活性的36%。瓦巴因选择性抑制α(2)异构体表明，含有α(1)异构体的异源二聚体比含有α(2)异构体的异源二聚体具有更高的Na+亲和力。对于alpha(1)beta(1)、alpha(2)beta(1)、alpha(1)beta(2)和alpha(2)beta(2)， Na+的估计K (m)值分别为4.0、5.5、7.5和13 mM。亲和差异和异构体分布表明，生理Na+浓度下的Na+，K+- atp酶的激活程度在不同肌肉（氧化和糖酵解）和不同异构体组成的亚细胞膜区域之间是不同的。这些差异可能对肌膜上的离子平衡产生影响。
Previous studies in expression systems have found different ion activation of the Na+/K+-ATPase isozymes, which suggest that different muscles have different ion affinities. The rate of ATP hydrolysis was used to quantify Na+,K+-ATPase activity, and the Na+ affinity of Na+,K+-ATPase was studied in total membranes from rat muscle and purified membranes from muscle with different fiber types. The Na+ affinity was higher (K (m) lower) in oxidative muscle compared with glycolytic muscle and in purified membranes from oxidative muscle compared with glycolytic muscle. Na+,K+-ATPase isoform analysis implied that heterodimers containing the beta(1) isoform have a higher Na+ affinity than heterodimers containing the beta(2) isoform. Immunoprecipitation experiments demonstrated that dimers with alpha(1) are responsible for approximately 36% of the total Na,K-ATPase activity. Selective inhibition of the alpha(2) isoform with ouabain suggested that heterodimers containing the alpha(1) isoform have a higher Na+ affinity than heterodimers containing the alpha(2) isoform. The estimated K (m) values for Na+ are 4.0, 5.5, 7.5 and 13 mM for alpha(1)beta(1), alpha(2)beta(1), alpha(1)beta(2) and alpha(2)beta(2), respectively. The affinity differences and isoform distributions imply that the degree of activation of Na+,K+-ATPase at physiological Na+ concentrations differs between muscles (oxidative and glycolytic) and between subcellular membrane domains with different isoform compositions. These differences may have consequences for ion balance across the muscle membrane.