Exogenous creatinine clearance accurately assesses filtration failure in rat experimental nephropathies

The purpose of this study was to determine whether creatinine clearance (Ccr), determined under conditions of exogenous creatinine infusion, accurately reflects glomerular filtration rate (GFR) in the rat. Normal rats and rats with either glomerulopathy (nephrotoxic serum nephritis, adriamycin nephropathy), ablative nephropathy, or acute renal failure (ischemic, HgCl2) were subjected to simultaneous Ccr and inulin clearance (Cin) determinations at a time that plasma creatinine concentrations were maintained at 10 to 20 mg/dL by exogenous creatinine infusion. Cin ranged from 0.02 to 2.49 mL/min, and a nearly perfect correlation with Ccr (r = .997) was obtained. Excellent correlations between Ccr and Cin were found in each of the individual study groups. When the rats were subdivided into groups according to their level of renal function (Cin greater than 1.5 mL/min; Cin 0.5 to 1.49 mL/min; Cin 0.02 to 0.49 mL/min), excellent correlations between Cin and Ccr were still observed (r = .93, .97, and .97, respectively). We concluded that exogenous Ccr accurately reflects GFR in the rat over the entire range of renal function and in a wide variety of experimental nephropathies. Given the simple methodology, exogenous Ccr could have substantial research application for assessing degrees of excretory function in experimental renal disease.