P2X6 Knockout Mice Exhibit Normal Electrolyte Homeostasis

ATP-mediated signaling is an important regulator of electrolyte transport in the kidney. The purinergic cation channel P2X6 has been previously localized to the distal convoluted tubule (DCT), a nephron segment important for Mg(2+) and Na(+) reabsorption, but its role in ion transport remains unknown. In this study, P2x6 knockout (P2x6(-/-)) mice were generated to investigate the role of P2X6 in renal electrolyte transport. The P2x6(-/-) animals displayed a normal phenotype and did not differ physiologically from wild type mice. Differences in serum concentration and 24-hrs urine excretion of Na(+), K(+), Mg(2+) and Ca(2+) were not detected between P2x6(+/+), P2x6(+/-) and P2x6(-/-) mice. Quantitative PCR was applied to examine potential compensatory changes in renal expression levels of other P2x subunits and electrolyte transporters, including P2x1-5, P2x7, Trpm6, Ncc, Egf, Cldn16, Scnn1, Slc12a3, Slc41a1, Slc41a3, Cnnm2, Kcnj10 and Fxyd2. Additionally, protein levels of P2X2 and P2X4 were assessed in P2x6(+/+) and P2x6(-/-) mouse kidneys. However, significant changes in expression were not detected. Furthermore, no compensatory changes in gene expression could be demonstrated in heart material isolated from P2x6(-/-) mice. Except for a significant (P<0.05) upregulation of P2x2 in the heart of P2x6(-/-) mice compared to the P2x6(+/+) mice. Thus, our data suggests that purinergic signaling via P2X6 is not significantly involved in the regulation of renal electrolyte handling under normal physiological conditions.