Van Why S K, Mann A S, Ardito T, Siegel N J, Kashgarian M
Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06510.
Am J Physiol. 1994 Jul;267(1 Pt 2):F75-85. doi: 10.1152/ajprenal.1994.267.1.F75.
Renal ischemia causes redistribution of Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) to the apical membrane of proximal tubules. We determined the time course of regeneration of Na(+)-K(+)-ATPase polarity and sought evidence of increased enzyme production during recovery as a means to restore polarity. Anesthetized rats underwent 45 min renal ischemia and reflow of 15 min, 2 h, 6 h, and 24 h. Immunofluorescent and electron microscopy showed loss of strict basolateral localization of Na(+)-K(+)-ATPase at 15 min reflow with repolarization by 24 h in sublethally injured cells. Both alpha 1- and beta-subunits were only in microsomal fractions at all reflow intervals. Immunodetectable levels of both subunits declined to 60-70% of control by 24 h reflow. Levels of mRNA for each subunit declined in parallel through 24 h to 55% of control. Overall transcription was profoundly depressed through 6 h but had recovered to near control by 24 h. Specific transcription of alpha 1- and beta-subunit mRNA was markedly decreased after ischemia and only partially recovered by 24 h. These results suggest that recycling of misplaced units rather than new Na(+)-K(+)-ATPase production is the means by which renal epithelia initially repolarize after ischemic injury.
肾缺血导致钠钾-腺苷三磷酸酶（Na(+)-K(+)-ATPase）重新分布至近端小管的顶端膜。我们确定了Na(+)-K(+)-ATPase极性再生的时间进程，并寻找恢复过程中酶产生增加的证据，以此作为恢复极性的一种方式。对麻醉大鼠进行45分钟的肾缺血，然后分别再灌注15分钟、2小时、6小时和24小时。免疫荧光和电子显微镜检查显示，在再灌注15分钟时，亚致死性损伤细胞中Na(+)-K(+)-ATPase的严格基底外侧定位丧失，到24小时时重新极化。在所有再灌注时间段，α1和β亚基均仅存在于微粒体组分中。到再灌注24小时时，两个亚基的免疫检测水平均降至对照的60 - 70%。每个亚基的mRNA水平在24小时内平行下降至对照的55%。总体转录在6小时内受到严重抑制，但到24小时时已恢复至接近对照水平。缺血后α1和β亚基mRNA的特异性转录显著降低，到24小时时仅部分恢复。这些结果表明，肾上皮细胞在缺血损伤后最初重新极化的方式是错位单位的再循环，而非新的Na(+)-K(+)-ATPase的产生。
