EXPRESSION OF Na^+-DEPENDENT GLUCOSE TRANSPORTERS (SGLT1, SGLT2) IN RAT KIDNEY PROXIMAL TUBULES.

在肾脏近端小管中，D-葡萄糖通过两步过程从管腔转运至血液：分别位于顶膜和基底外侧膜的Na+依赖性/非依赖性葡萄糖转运蛋白（SGLT 1，2/GLUTI，2）。在远端部分的肾小管中，仅GLUT 1在基底外侧膜上表达以从血液中吸收D-葡萄糖。采用北方印迹法（Northern blot）研究了新生大鼠肾小管中SGLT 1、SGLT 2和GLUTi mRNA在早期发育阶段（4-15 d）的表达变化。SGLTIMRNA表达水平随发育进程逐渐升高，5 d为100%，10 d为330%，15 d为720%。其次，SGLT 2 mRNA表达水平增加：100%（5 d），280%（10 d）和42%（15 d）。最后，GLUT 1 mRNA表达水平增加：100%（5 d），118%（10 d）和132%（15 d）。注射倍他米松（60 μ g/100 g体重）。，（第30页）增加4-9（5日龄大鼠）和2-3（15日龄大鼠）的SGLT 1、SGLT 2和GLUTi mRNA表达水平。这些结果表明，Na+依赖性/非依赖性葡萄糖转运蛋白mRNA的表达在4-15日龄的发育过程中逐渐增加，说明在新生儿早期，beta3对葡萄糖转运蛋白的诱导作用更强。

In kidney proximal tubules, D-glucose is transported from the lumen to the blood via two-step processes : Na+-dependent/independent glucose transporters (SGLT1, 2/GLUTI, 2) at both apical and basolateral membranes, respectively. In kidney tubules of distal portions, only GLUT1 is expressed at the basolateral membrane to absorb D-glucose from the blood. Using Northern blot analysis we investigated the changes of the SGLT1, SGLT2, and GLUTi mRNA expressions in neonatal rat kidney tubules during early developmental period (4-15 days). A level of SGLTImRNA expression increased on the process of development : 100% (5 d), 330% (10 d), and '720% (15 d). Secondarily, a level of SGLT2 mRNA expression increased : 100% (5 d), 280% (10 d), and 42% (15 d). Finally, a level of GLUT1 mRNA expression increased : 100% (5 d), 118% (10 d), and 132% (15 d). Injection of betamethasone (60mug/100 g body wt. , i. p.) increased the level of SGLT1, SGLT2, and GLUTi mRNA expressions by 4-9 (5-day-old rats) and by 2-3 (15-day-old rats). These results indicate that the expression of Na+-dependent /independent glucose transporters mRNA increased during the developmental period of 4-15 days and strongly suggest that betamethasone is more effective in induction of the expression of the glucose transporters at earlier period of neonates.