PRESENCE AND DIFFERENTIAL EXPRESSION OF SGLT1, GLUT1, GLUT2, GLUT3 AND GLUT5 HEXOSE-TRANSPORTER MESSENGER-RNAS IN CACO-2 CELL CLONES IN RELATION TO CELL-GROWTH AND GLUCOSE CONSUMPTION

Seven clones from the Caco-2 cell line, three isolated from passage 29 (PD7, PD10, PF11) and four from passage 198 (TB10, TC7, TF3, TG6), al l of them selected on the basis of differences in the levels of expres sion of sucrase-isomaltase and rates of glucose consumption, were anal ysed for the expression of hexose-transporter mRNAs (SGLT1, GLUT1-GLUT 5) in relation to the phases of cell growth and the associated variati ons of the rates of glucose consumption. All clones showed a similar p attern of evolution of the rates of glucose consumption, which decreas ed from the exponential to the late-stationary phase, but differed, in a 1-40-fold range, in the values observed at late post-confluency. Ac cording to these values, clones could be divided into high- (PD10, PF1 1) and low-glucose-consuming cells (PD7, TB10. TC7, TF3 and TG6). GLUT 1 and GLUT3 mRNAs were expressed in all clones and showed a similar pa ttern of evolution: their level decreased, from the exponential to the stationary phase, in close correlation with the decrease in rates of glucose consumption, with only high-glucose-consuming clones maintaini ng high levels in the stationary phase. In contrast, SGLT1, GLUT2 and GLUT5 mRNAs were only expressed, like sucrase-isomaltase mRNA, in the low-glucose-consuming clones, and their level increased from the expon ential to the stationary phase, in parallel with the differentiation o f the cells. GLUT4 was undetectable in all the clones. Glucose depriva tion generally resulted in a discrete decrease in the levels of all tr ansporter mRNAs in all clones, one exception being GLUT2, which in the high-glucose-consuming clones is only detectable when the cells are g rown in low glucose. These clones should be ideal tools with which to study in vitro, at the single-cell level, how these transporters concu r to the utilization and transport of hexoses and how their exclusive or co-ordinated expression is regulated.