Renal endothelin-1 (ET-1) and purinergic signaling systems regulate [Na.sup.+] reabsoiption in the renal medulla. A link between the renal ET-1 and purinergic systems was demonstrated in vitro, however, the in vivo interaction between these systems has not been defined. To test whether renal medullary activation of purinergic (P2) receptors promotes ET-dependent natriuresis, we determined the effect of increased medullary NaCl loading on [Na.sup.+] excretion and inner medullary ET-1 mRNA expression in anesthetized adult male Sprague-Dawley rats in the presence and absence of purinergic receptor antagonism. Isosmotic saline (NaCl; 284 mosmol/kg[H.sub.2]O) was infused into the medullary interstitium (500 [micro]l/h) during a 30-min baseline urine collection period, followed by isosmotic or hyperosmotic saline (1,800 mosmol/kg[H.sub.2]O) for two further 30-min urine collection periods. [Na.sup.+] excretion was significantly increased during intramedullary infusion of hyperosmotic saline. Compared with isosmotic saline, hyperosmotic saline infused into the renal medulla caused significant increases in inner medullary ET-1 mRNA expression. Renal intramedullary infusion of the P2 receptor antagonist suramin inhibited the increase in [Na.sup.+] excretion and inner medullary ET-1 mRNA expression induced by NaCl loading in the renal medulla. Activation of medullary [P2Y.sub.2/4] receptors by infusion of UTP increased urinary Na+ excretion. Combined [ET.sub.A] and [ET.sub.B] receptor blockade abolished the natriuretic response to intramedullary infusion of UTP. These data demonstrate that activation of medullary P2 receptors promotes ET-dependent natriuresis in male rats, suggesting that the renal ET-1 and purinergic signaling systems interact to efficiently facilitate excretion of a NaCl load. endothelin-1; purinergic receptors; natriuresis; kidney; inner medulla doi: 10.1152/ajprenal.00090.2016.