Asher C, Singer D, Eren R, Yeger O, Dascal N, Garty H
Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.
Am J Physiol. 1992 Feb;262(2 Pt 1):G244-8. doi: 10.1152/ajpgi.1992.262.2.G244.
RNA was isolated from chicken lower intestine (both colon and coprodeum) and injected into Xenopus oocytes. 22Na+ fluxes measured after 1-4 days demonstrated the induction of an amiloride-blockable pathway. The Na+ transporter expressed by the exogenous RNA had a high affinity to amiloride (inhibitory constant less than 0.1 microM), but was insensitive to ethylisopropyl amiloride, i.e., it is likely to be the apical Na+ channel. Functional channels were readily expressed in oocytes injected with RNA derived from chickens fed a low-NaCl diet. On the other hand, no channel activity was detected in oocytes injected with RNA isolated from chickens fed a high-NaCl diet. Thus the previously reported regulation of transport by the dietary NaCl intake involves modulations in the level of mRNA that codes either for the Na+ channel or a posttranscriptional regulator of the channel.
从鸡的下肠道（结肠和泄殖腔）分离出RNA，并将其注射到非洲爪蟾卵母细胞中。1 - 4天后测量的22Na+通量表明诱导了一种可被氨氯吡脒阻断的途径。由外源RNA表达的Na+转运蛋白对氨氯吡脒具有高亲和力（抑制常数小于0.1微摩尔），但对乙基异丙基氨氯吡脒不敏感，即它可能是顶端Na+通道。功能性通道在注射了来自低NaCl饮食喂养鸡的RNA的卵母细胞中很容易表达。另一方面，在注射了从高NaCl饮食喂养鸡分离的RNA的卵母细胞中未检测到通道活性。因此，先前报道的饮食NaCl摄入量对转运的调节涉及编码Na+通道或该通道转录后调节因子的mRNA水平的调节。
