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到血液：分别位于顶膜和基底外侧膜的钠依赖/独立葡萄糖转运体(SGLT1，2/GLUTI，2)。在远端肾小管中，只有GLUT1在基底膜上表达，以吸收血液中的D-葡萄糖。用Northern印迹法研究了新生大鼠早期(4~15天)肾小管SGLT1、SGLT2和GLUTImRNA表达的变化。SGLTImRNA的表达水平在发育过程中逐渐升高，分别为100%(5d)、330%(10d)和720%(15d)。其次，SGLT2 mRNA表达水平升高：100%(5d)、280%(10d)和42%(15d)。最后，GLUT1基因表达水平升高：100%(5天)、118%(10天)和132%(15天)。注射倍他米松(60 mg/100g体重，ip)。使SGLT1、SGLT2和GLUTimRNA表达水平分别增加4~9天(5日龄)和2~3天(15日龄)。这些结果表明，Na+依赖/非依赖葡萄糖转运体mRNA的表达在4~15天的发育期明显增加，提示倍他米松对新生儿早期葡萄糖转运体的表达具有更强的诱导作用。

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.