ATP inhibits Mg2+ uptake in MDCT cells via P2X purinoceptors

Nucleotides have diverse effects on water and electrolyte reabsorption within the distal tubule of the nephron. As the distal tubule is important in control of renal Mg2+ balance, we determined the effects of ATP on cellular Mg2+ uptake in this segment. The effects of ATP on immortalized mouse distal convoluted tubule (MDCT) cells were studied by measuring Mg2+ uptake with fluorescence techniques. The mean basal Mg2+ uptake rate was 165 +/- 6 nM/ s. ATP inhibited basal Mg2+ uptake and hormone-stimulated Mg2+ entry by 40%. Both P2X (P2X1-P2X5 subtypes) and P2Y2 receptor subtypes were identified in MDCT cells using differential RT-PCR. Activation of both receptor subtypes with selective agonists increased intracellular Ca2+ concentration, P2X purinoceptors by ionotropic-gated channels, and P2Y receptors via G protein-mediated intracellular Ca2+ release. The more relatively selective P2X agonists [beta, gamma -methylene ATP (beta, gamma -Me-ATP) and 2'- and 3'-O-(4-benzoyl-benzoyl)-ATP] inhibited arginine vasopressin (AVP)- and parathyroid hormone (PTH)- mediated Mg2+ uptake whereas agonists more selective for P2Y purinoceptors (UTP, ADP, and 2-methylthio-ATP) were without effect. Removal of extracellular Ca2+ diminished beta, beta -Me-ATP-mediated increase in intracellular Ca2+ and inhibition of AVP-stimulated Mg2+ entry. We conclude from this information that ATP inhibited Mg2+ uptake in MDCT cells through P2X purinoceptors expressed in this distal convoluted tubule cell line.