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

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 beta-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/l (SEM) (p less than or equal to 0.01). Glomerular filtration rate increased from 116 +/- 2 to 123 +/- 3 ml/mi x 1.73 m2 (p less than or equal to 0.01), while no change in renal plasma flow was seen - 552 +/- 11 versus 553 +/- 18 ml/min x 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/l and clamped by means of an 'artificial beta cell'. Glomerular filtration rate increased in all patients, from 133 +/- 5 to 140 +/- 6 ml/min x 1.73 m2 (p less than or equal to 0.02), as did renal plasma flow from 576 +/- 26 to 623 +/- 38 ml/min x 1.73 m2 (p less than or equal to 0.02). Urinary albumin excretion remained unchanged in both normal subjects and diabetics. beta-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.