Arginine vasopressin regulates CFTR and ClC-2 mRNA expression in rat kidney cortex and medulla

The presence of both CFTR and ClC-2 proteins in the kidney suggest that they are involved in chloride transport along the nephron but their physiological roles in this organ are not known. To further understand the role of these chloride channels we studied Wistar rats subjected to dehydration for 2 days and also the homozygous Brattleboro rats, a strain of Long-Evans rats carrying an autosomal recessive mutation that leads to a deficiency of arginine-vasopressin (AVP) secretion in the plasma. The expression of CFTR was increased in the medulla of dehydrated Wistar rats and no variation was observed in the cortex. The expression of both ClC-2 and CFTR mRNAs was low in the renal cortex and medulla of the homozygous Brattleboro rats but returned to normal levels after AVP reposition. By the use of Madine-Darby canine kidney (MDCK) type I epithelial cells, it was observed that AVP (10(-8), 10(-7) and 10(-6) M) increased CFTR mRNA expression "in vitro" but no effect was observed when changes in the medium tonicity were caused by the addition of sucrose, NaCl, manitol or urea. The modulation of both CFTR and ClC-2 mRNA by AVP, the main hormone involved in the regulation of body fluid osmolality, suggests the participation of these two chloride channels in the renal tubule transcellular chloride transport modulated by AVP.