Urine Glucose Concentrations During Intravenous Glucose Tolerance Tests in Horses
ACVIM 2008
F.Tóth1; N. Frank1; K. Perdue1; R. Geor2; S.B. Elliott1; R.C. Boston3
1University of Tennessee College of Veterinary Medicine, Knoxville, TN, USA 2Middleburg Agricultural Research and Extension Center, Virginia Polytechnic and State University, Middleburg, VA, USA; 3University of Pennsylvania, Kennett Square, PA, USA

When intravenous glucose tolerance tests are used, area under the blood glucose curve (AUCg) values are calculated, and it is assumed that blood glucose levels decline in response to insulin. However, it has not been determined whether blood glucose concentrations also decrease as a result of glucose loss into the urine. We hypothesized that urine glucose concentrations would increase significantly during the combined glucose-insulin tolerance test (CGIT) and frequently-sampled intravenous glucose tolerance (FSIGT) test in healthy adult horses. A new FSIGT test was also designed with the aim of eliminating glucose loss into the urine. Six horses were included in a crossover study. Treatments included the CGIT, which involves infusion of 150 mg/kg dextrose and 100 mU/kg insulin, and two different FSIGT tests: the established procedure using 300 mg/kg dextrose and 30 mU/kg insulin and a new test using 100 mg/kg dextrose and 20 mU/kg insulin dosages. Urine samples were collected every 10 minutes via a catheter inserted into the urinary bladder. Mean urine AUCg curve values were calculated for each procedure. Treatment effects were evaluated using ANOVA.

Glucosuria was detected and urine glucose concentrations increased significantly over time during each of the tests. Mean urine AUCg values differed significantly (P < 0.001) between groups, with the lowest value registered for the new FSIGT test. Results demonstrate that glucosuria develops during intravenous glucose tolerance tests in horses and this may affect AUCg. This problem was not resolved by selecting a lower dextrose dosage of 100 mg/kg.

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Ferenc Tóth

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