Hyperglycemia with and without glycosuria: effect on inulin and para-amino hippurate clearance

The response of the clearance of inulin (Cin) and para-amino hippurate (CPAH) to acute hyperglycemia with and without glycosuria was investigated in ten, healthy non-diabetic subjects. Standard methodology (UV/P) was used, with a mean clearance calculated from three, 15-minute urine collection periods. Each subject was studied at three levels of blood glucose (mmol/liter) concentration, mean (SE): Level 1, fasting, 4.5 (0.1); Level 2, hyperglycemia below renal threshold for glucose, 7.2 (0.1); Level 3, hyperglycemia with glycosuria, 12.6 (0.5). There was a significant rise in mean Cin (ml/min/1.73 m2) when changing from Level 1 (112[3]) to Level 2 (121[5]), with no further increase on changing to Level 3 (122[4]). With glycosuria Cin fell in some subjects. Mean CPAH (ml/min/1.73 m2) increased through Level 1 (560[27]) to Level 3 (603[34]), with consequently no change in mean filtration fraction at the three levels of glycemia. Our observations show a rise in glomerular filtration rate with mild hyperglycemia below renal threshold, with no further increase during hyperglycemia sufficient to produce glycosuria.