COMPARISON OF STANDARD AND RADIONUCLIDE METHODS FOR MEASUREMENT OF GLOMERULAR FILTRATION RATE AND EFFECTIVE RENAL BLOOD FLOW IN FEMALE HORSES

Comparison of standard and radionuclide methods for measuring glomerular filtration rate (GFR) and effective renal blood flow (ERBF) was performed in 8 healthy female horses. Inulin and p-aminohippurate solutions were administered IV as a bolus, followed by sustained administration. Urine and plasma inulin and p-aminohippurate concentrations and urine volume were measured. Glomerular filtration rate and ERBF were calculated on the basis of these measurements. Glomerular filtration rate and ERBF were measured on the basis of plasma clearance of the radiopharmaceuticals, 99mTc-labeled diethylene-triaminepentaacetic acid (99mTc-DTPA) and [131I]-o-iodohippuric acid (131I-OIH), respectively. Mean +/- SEM GFR, using inulin, was 1.83 +/- 0.21 ml/min/kg of body weight. Mean GFR, using 99mTc-DTPA was 1.79 +/- 0.18 ml/min/kg. Mean ERBF, using p-aminohippurate, was 15.13 +/- 1.28 ml/min/kg. Mean ERBF, using 131I-OIH, was 18.42 +/- 1.57 ml/min/kg. Analysis of variance indicated no significant difference between mean values for GFR and ERBF. Radionuclide measurement of GFR and ERBF compared well with standard methods and is an alternative technique to the cumbersome standard methods for determination of GFR and ERBF in horses.