The effect of angiotensin II infusion on the renal transport of purine bases and oxypurinol (a metabolite of allopurinol) was investigated in 5 healthy subjects who were orally given allopurinol (300 mg) 9 hours prior to the study. Angiotensin II was intravenously administered at 8 ng/min/kg for 2 hours. The fractional clearances of uric acid, xanthine, and oxypurinol were significantly decreased during angiotensin II infusion; however, that of hypoxanthine did not change. The urinary excretion levels of uric acid, xanthine, and oxypurinol were also significantly decreased during angiotensin II infusion. These results suggest that angiotensin II infusion affected the renal clearances of uric acid, xanthine, and oxypurinol through direct tubular transport and/or hemodynamic changes. Accordingly, the hypouricemic effect of allopurinol may be exaggerated in hypertensive gout patients with an enhanced renin-angiotensin system, since an increased biological half-life of oxypurinol is expected in these patients.
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