Renal Clearance of [14C]oxalate: Comparison of Constant-Infusion with Single-Injection Techniques

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Abstract
The renal clearance of [14C]oxalate was assessed by the constant-infusion technique and single-injection technique (plasma sampling only: 1-compartment and 2-compartment model; plasma and urine sampling). Healthy volunteers and patients with renal stones were studied. Results with the constant-infusion techniques (with and without urine sampling) were not significantly different from each other. The renal clearance of [14C]oxalate measured with the single-injection technique as compared with the constant-infusion technique was overestimated in the single-injection 1-compartment model (52%) and in the 2-compartment model (30%). The calculated level of plasma oxalate in the healthy volunteers ranged from 1.04 to 1.78 .mu.mol/l (mean 1.39). The biological half-life of [14C]oxalate, estimated by the cumulative excretion of 14C in urine after equilibrium was established, was 128 min (range: 113-142 min). The oxalate/creatinine clearance ratio in the healthy volunteers ranged from 1.73 to 2.22 (mean 2.01).