OBJECTIVE Identification and optimization of 2-(3-fluorophenyl)-4-butylamino-pyrazole [4,3-C]-quinoline-3-ketone derivatives as potent selective A1 adenosine receptor antagonists and evaluation of preliminary pharmacological profile in unique diuretic activity.METHODS 2-(3-Fluorophenyl)-4-butylamino-pyrazole [4,3-C]-quinoline-3-ketone derivatives binding affinity and selectivity as well as activity were evaluated by radioligand-binding assays and [35S]-GTPγS filtration assays, respectively in cell lines stably expressed human A1 adenosine receptor and human A2A adenosine receptor; the diuretic effects were preliminarily evaluated in normal rats and cisplatin-induced acute renal failure rats.RESULTS (1) Using radioligand-binding assays, five 2-(3-fluorophenyl)-4-butylamino-pyrazole [4,3-C]-quinoline-3-ketone derivatives with high affinity and selectivity for A1 adenosine receptor were obtained.PQ-69 presented the highest affinity and selectivity for A1 adenosine receptor among the 5 compounds.PQ-69 showed Ki-high 0.12 fmol ·L-1/Ki-low 1.2 nmol ·L-1 for A1 adenosine receptor and exhibited 1.5 × 109-fold binding selectivity for A1 vs A2A adenosine receptor.Furthermore, as a typical A1 adenosine receptor antagonist, PQ69 dose-dependently inhibited the effect of R-PIA, a selective adenosine A1 receptor agonist.Further studies were designed to find whether PQ-69 has potent selectivity in mice lacking A1 receptor or through blockade of A1 receptors.(2) In saline treated rats, PQ-69 (3, 10 and 30 mg·kg-1, ig) dose-dependently increased urine flow to the same extent as hydrochlorothiazide (3 mg·kg-1) but did not induce electrolytes imbalance.In cisplatin-induced acute renal failure rats, compared to Furosemide (30 mg·kg-1), PQ-69 (10, 30 mg·kg-1, ig) improved creatinine clearance and did not affect sodium, potassium excretion.(3) Preliminary evaluation of the pharmacokinetics showed that PQ69 displayed good solubihty and absorption.Acute toxicity test showed that oral administration of PQ-69 (2100 mg· kg-1) did not lead to death in both male and female mice.DISCUSSION PQ-69, a novel and potent non-xanthine-like A1 adenosine receptor antagonist, induced potent diuresis and improved creatinine clearance in normal or acute renal failure rats with low toxicity.In view of our study, 2-(3-fluorophenyl)-4-butylamino-pyrazole [4,3-C]-quinoline-3-ketone has a future in the treatment of acute heart failure, hypertension as well as edema.