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

Abstract

The response of the clearances of inulin (C(in)) and para-amino hippurate (C(PAH)) 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 C(in) (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 C(in) fell in some subjects. Mean C(PAH) (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.