Serial determination of glomerular filtration rate in conscious mice using FITC-inulin clearance

Two nonradioactive methods for determining glomerular filtration rate (GFR) in conscious mice using FITC-labeled inulin (FITC-inulin) were evaluated. The first method measured GFR using clearance kinetics of plasma FITC-inulin after a single bolus injection. Based on a two-compartment model, estimated GFR was 236.69 +/- 16.55 and 140.20 +/- 22.27 microl/min in male and female C57BL/6J mice, respectively. Total or (5/6) nephrectomy reduced inulin clearance to 0 or 32.80 +/- 9.32 microl/min, respectively. Conversely, diabetes mellitus induced by streptozotocin was associated with increased GFR. The other approach measured urinary inulin clearance using intraperitoneal microosmotic pumps to deliver FITC-inulin and metabolic cages to collect timed urine samples. This approach yielded similar GFR values of 211.11 +/- 26.56 and 157.36 +/- 20.02 microl/min in male and female mice, respectively. These studies demonstrate the feasibility of repeated nonisotopic measurement of inulin clearance in conscious mice.