Ghishan F K, Arab N
Vanderbilt University, Department of Pediatrics, Nashville, Tennessee 37232.
Pediatr Res. 1988 Jun;23(6):612-5. doi: 10.1203/00006450-198806000-00017.
The transport of phosphate into jejunal endoplasmic reticulum vesicles isolated from suckling and adolescent rats was investigated using a rapid filtration technique. Intestinal endoplasmic reticulum from both ages were enriched with NADPH cytochrome-C-reductase whereas other markers for brush border, basolateral, mitochondrial, and Golgi apparatus were impoverished. Phosphate uptake represented an energy-dependent process as evident by more than 80% decrease in uptake values at 0 degrees C compared to 25 degrees C. Phosphate uptake was ATP dependent in both age groups, however, mean uptake values were significantly greater in suckling rats compared to adolescent rats. pH optimum for uptake was 7.2 p-Chloromercuribenzoate at 100 microM concentration inhibited phosphate uptake by more than 90%. Initial rate of phosphate uptake was linear up to 45 s. Kinetics of phosphate uptake at 30 s showed a Km of 0.7 +/- 0.1 and 0.15 +/- 0.1 suckling and adolescent rats, respectively. Vmax was 1.5 +/- 0.5 and 0.14 +/- 0.01 nmol/mg protein/30 s for both suckling and adolescent rats, respectively. Herein we provide evidence for the first time for the presence of a phosphate carrier in intestinal endoplasmic reticulum of rats. Endoplasmic reticulum of phosphate uptake was significantly greater in suckling rats compared to adolescent rats. This increase in uptake is due to a greater number and activity of phosphate carriers in suckling rats.
采用快速过滤技术，研究了从乳鼠和青春期大鼠分离的空肠内质网囊泡对磷酸盐的转运。两个年龄段大鼠的肠内质网中NADPH细胞色素C还原酶含量丰富，而刷状缘、基底外侧、线粒体和高尔基体的其他标志物含量较低。磷酸盐摄取是一个能量依赖过程，与25℃相比，0℃时摄取值下降超过80%，这一现象很明显。两个年龄组的磷酸盐摄取均依赖ATP，然而，乳鼠的平均摄取值显著高于青春期大鼠。摄取的最适pH值为7.2。100微摩尔浓度的对氯汞苯甲酸抑制磷酸盐摄取超过90%。磷酸盐摄取的初始速率在45秒内呈线性。30秒时磷酸盐摄取的动力学显示，乳鼠和青春期大鼠的Km值分别为0.7±0.1和0.15±0.1。乳鼠和青春期大鼠的Vmax分别为1.5±0.5和0.14±0.01纳摩尔/毫克蛋白质/30秒。在此，我们首次提供证据表明大鼠肠内质网中存在磷酸盐载体。与青春期大鼠相比，乳鼠内质网的磷酸盐摄取量显著更高。摄取量的增加是由于乳鼠中磷酸盐载体的数量和活性更高。
