Expression of aldose reductase and sorbitol dehydrogenase genes in Schwanncells isolated from rat: effects of high glucose and osmotic stress

To investigate the polyol pathway activity in Schwann cells, we determined the mRNA levels of aldose reductase (AR) and sorbitol dehydrogenase (SDH) i n cultured cells under hyperglycemic or hyperosmotic conditions using compe titive RT-PCR technique. The expressions of AR and SDH mRNAs in Schwann cel ls were unaltered by high (30 mM) glucose content in the medium. On the oth er hand, osmotic stress elicited significant increases in AR mRNA without a ny effect on SDH mRNA expression. The levels of AR mRNA determined by this RT-PCR system were significantly correlated with AR activity, as well as th e levels of sorbitol accumulated in Schwann cells cultured under hyperosmot ic conditions. These findings suggest that in contrast to the induction of AR expression by osmotic stress, high glucose per se does not up-regulate e xpression of the enzymes constituting the polyol pathway in Schwann cells. The RT-PCR system developed in this study may be a useful tool in ascertain ing the relative contributions of AR and SDH to the metabolic derangements leading to diabetic complications. (C) 2001 Elsevier Science B.V. All right s reserved.