EXPRESSION OF NA+ CL-/BETAINE AND NA+/MYO-INOSITOL TRANSPORTERS, ALDOSE REDUCTASE AND SORBITOL DEHYDROGENASE IN MACULA DENSA CELLS OF THE KIDNEY/

It has been suggested that macula densa cells may be exposed to hypero smotic stress. Since chronic exposure to hypertonic stress causes the amount of intracellular organic osmolytes to increase, the expression of transporters and enzymes that participate in the intracellular accu mulation of organic osmolytes was examined using non-radioactive in si tu hybridization in the macula densa region of control rats and furose mide-treated animals. Both the sodium- and chloride-dependent betaine transporter (BGT) and sodium-dependent myo-inositol transporter (SMIT) were expressed preferentially in macula densa cells and for both mRNA s the signal intensity was visibly reduced by furosemide, The enzymes aldose reductase (which mediates the conversion of glucose to sorbitol ) and sorbitol dehydrogenase (which converts sorbitol into fructose) w ere expressed not only in macula densa cells but also in the surroundi ng tubular cells, and the expression was insensitive to furosemide. Th us it remains unclear whether the expression of BGT and SMIT is relate d to a putative hypertonic juxtaglomerular region.