Effect of intravenous glucose infusion on renal function in normal man and in insulin-dependent diabetics

Summary The effect of intravenous glucose infusion on glomerular filtration rate and renal plasma flow (constant infusion technique using ¹²⁵I-iothalamate and ¹³¹I-hippuran) and on urinary excretion of albumin and -2-microglobulin were studied in ten normal subjects and seven metabolically well-controlled insulin-dependent diabetics. Following glucose infusion in normal subjects (n = 10) blood glucose increased from 4.7±0.1 to 10.9±0.4 mmol/1 (SEM) (p 0.01). Glomerular filtration rate increased from 116±2 to 123±3ml/min x 1.73 m² (p 0,01), while no change in renal plasma flow was seen 552±11 versus 553±18 ml/min × 1.73 m². Volume expansion with intravenous saline infusion in six of the normal subjects induced no changes in blood glucose or kidney function. In seven strictly controlled insulin-dependent diabetics, blood glucose values were raised from 4.6±0.4 to 16.0±0.6 mmol/1 and clamped by means of an artificial beta cell. Glomerular filtration rate increased in all patients, from 133 ±5 to 140±6 ml/min × 1.73 m² (p 0.02), as did renal plasma flow from 576±26 to 623±38 ml/ min × 1.73 m² (p 0.02). Urinary albumin excretion remained unchanged in both normal subjects and diabetics. -2-microglobulin excretion rate increased significantly in the diabetics following glucose infusion, while no significant change was seen in the normal subjects. Our results show that hyperglycaemia per se contributes to the increased glomerular filtration rate and renal plasma flow in insulin-dependent diabetes.