Lücking K, Nielsen J M, Pedersen P A, Jørgensen P L
Biomembrane Research Centre, August Krogh Institute, Copenhagen University, Denmark.
Am J Physiol. 1996 Aug;271(2 Pt 2):F253-60. doi: 10.1152/ajprenal.1996.271.2.F253.
For understanding the regulation of sodium reabsorption, it is important to know whether the alpha 2- or alpha 3-isoform of Na-K-adenosinetriphosphatase (Na-K-ATPase) is expressed in mammalian kidney in addition to the predominant alpha 1 beta 1-isozyme. Here we applied competitive polymerase chain reaction (PCR) for estimation of mRNA in parenchymal zones of rat kidney for comparison to high-affinity [3H]ouabain binding. The alpha 3-isoform mRNA was demonstrated to form 0.04-0.05% of the amount of alpha 1-isoform mRNA in the cortex, medulla, and papilla of rat kidney. The alpha 2-mRNA was demonstrated in all three zones and constituted 0.03% of the amount of alpha 1-mRNA in cortex. The abundance of the alpha 1 truncated mRNA was 0.1-0.8% of that of the alpha 1-mRNA. The upper limit for expression of Na-K-ATPase isozyme with high ouabain affinity (dissociation constant, 69-141 nM) was 0.096-0.14% of the concentration of alpha 1 beta 1-Na-K-ATPase. Thus a small but well-defined pool of alpha 2- and alpha 3-isoforms constitutes < or = 0.1% of the amount of alpha 1-isoform at both the mRNA and protein level in rat kidney.
为了解钠重吸收的调节机制，除了主要的α1β1同工酶外，了解钠钾三磷酸腺苷酶（Na-K-ATPase）的α2或α3同工型是否在哺乳动物肾脏中表达很重要。在此，我们应用竞争性聚合酶链反应（PCR）来估计大鼠肾脏实质区的mRNA，以便与高亲和力[3H]哇巴因结合进行比较。结果表明，在大鼠肾脏的皮质、髓质和乳头中，α3同工型mRNA占α1同工型mRNA量的0.04 - 0.05%。在所有三个区域均检测到α2-mRNA，其在皮质中占α1-mRNA量的0.03%。α1截短mRNA的丰度为α1-mRNA的0.1 - 0.8%。具有高哇巴因亲和力（解离常数为69 - 141 nM）的Na-K-ATPase同工型的表达上限为α1β1-Na-K-ATPase浓度的0.096 - 0.14%。因此，在大鼠肾脏的mRNA和蛋白质水平上，一小部分但明确的α2和α3同工型池占α1同工型量的≤0.1%。
