Peterson D R, Kubillus S, Binstock W, Zikos D
Department of Physiology and Biophysics, University of Health Sciences, Chicago Medical School, Illinois 60064.
Am J Physiol. 1989 Feb;256(2 Pt 1):C304-9. doi: 10.1152/ajpcell.1989.256.2.C304.
To examine the effects of molecular charge on membrane processing in renal tubular cells, the distribution of cationic and anionic ferritin was characterized in microperfused proximal nephron segments. During the first 7 min of proximal tubule perfusion, cationic ferritin was observed 1) bound to the brush-border membrane, 2) in apically positioned vesicles and vacuoles, 3) in lysosomes, 4) in vesicles adjacent to the basolateral plasmalemma, and 5) bound to the basolateral plasmalemma. Compared with anionic ferritin, the distribution of cationic ferritin was characterized by 1) a smaller relative grain density for lysosomes, 2) an accumulation of granules in an enlarged pool of apical cytoplasmic vesicles and vacuoles, and 3) a greater number of granules reaching the basolateral plasmalemma. During incubation directly in the presence of isolated renal cortical microvilli, binding of cationic ferritin increased significantly as pH was lowered from 8.0 to 4.5 and was greater than that of anionic ferritin, which varied little with pH. The data indicate that the molecular charge of endocytosed substances affects routing and membrane processing in proximal tubular cells, suggesting that their membrane-binding characteristics may influence transport patterns.
为研究分子电荷对肾小管细胞中膜处理的影响，在微灌注的近端肾单位节段中对阳离子铁蛋白和阴离子铁蛋白的分布进行了表征。在近端小管灌注的最初7分钟内，观察到阳离子铁蛋白：1）结合在刷状缘膜上；2）存在于顶端定位的囊泡和液泡中；3）存在于溶酶体中；4）存在于与基底外侧质膜相邻的囊泡中；5）结合在基底外侧质膜上。与阴离子铁蛋白相比，阳离子铁蛋白的分布特点为：1）溶酶体的相对颗粒密度较小；2）在扩大的顶端细胞质囊泡和液泡池中颗粒积累；3）到达基底外侧质膜的颗粒数量更多。在直接与分离的肾皮质微绒毛一起孵育期间，随着pH从8.0降至4.5，阳离子铁蛋白的结合显著增加，且大于阴离子铁蛋白，后者随pH变化不大。数据表明，内吞物质的分子电荷影响近端小管细胞中的转运途径和膜处理，提示它们的膜结合特性可能影响转运模式。
