Effect of renal medullary interstitial infusions of hyperosmotic saline (1,800 mosmol/kgH2O) with or without the nonselective antagonist of purinergic (P2) receptors, suramin, on urine flow (A), UNaV (B), UKV (C), and urine osmolality (D) in anesthetized male rats. Data are means ± SE of 5–6 samples in each group. Error bars for some time points are not apparent due to very low SE. *P < 0.05 vs. corresponding baseline values. †P < 0.05 vs. corresponding hyperosmotic saline values.