Renal clearance of glucose in hypothermic dogs

¹ Department of Physiology, Albany Medical College, Albany, New York

Quantitative alterations in both glomerular filtration (GFR) and tubular reabsorption of glucose, before, during and after onset of hypothermia were investigated. Urine was collected by direct cannulation of ureters and arterial blood obtained from a femoral cannula. Creatinine was used to measure GFR and glucose was analyzed by the glucose-oxidase method. During control period (rectal temp. 38°C) it was found that onlg a trace (17 ± 4 mg %) (.09 ± .02 mg/min.) of glucose spilled over into the urine. With the development of hypothermia a progressive fall in glomerular filtration rate was observed (78 ± 5 ml/min. at control rectal temp. (R.T.) to 30 ± 5 ml/min. at R.T. of 25°C). In spite of the fact that less fluid was filtered across the glomerulus, both urine volume and glucose excretion increased markedly (373 ± 122 mg %) (4.3 ± 1.9 mg/min.) at R.T. of 25°C. There is obviously a twofold effect of hypothermia on renal function, physically via the cardiovascular system resulting in a falling GFR and chemically on the tubular reabsorptive processes resulting in a decreased glucose reabsorption. To study the kinetics of this decreased glucose reabsorption, glucose Tm was investigated. It was found that control glucose Tm averaged 380 mg/min. (the E/F ratio being 52%). At 27°C R.T. the Tm was 103 mg/min. (E/F ratio being 73%).

Note:
With the Technical Assistance of Miss R. H. Lubinski and Mrs. I. M. Mielens