Glomerular hyperfiltration and blood viscosity in type I (insulin-dependent) diabetic subjects.

To investigate whether the increased glomerular filtration rate (GFR) in short-term diabetic patients is related to increased blood- or plasma viscosities, GFR [( 51Cr] EDTA-clearance), whole blood- and plasma viscosities were simultaneously determined in 16 insulin-dependent diabetic subjects, aged 11 to 34 years (duration of disease 0.1 to 8 years) and compared to the results in healthy subjects. Mean standard GFR +/- SD (that is, GFR corrected to body surface area of 1.73 m2) was significantly higher in the diabetics than in 16 age- and sex matched controls (142 +/- 26 ml/min vs. 123 +/- 18 ml/min, P less than 0.02). Blood viscosities at different shear rates and the plasma viscosity were not significantly different in the two groupes , although the plasma fibrinogen level was significantly elevated in the diabetics (376 +/- 60 mg%, vs. 289 +/- 37 mg%, P less than 0.001). No correlation was found between GFR and the viscosity measurements. The results of the present study do not support the suggestion that the increased GFR in short-term diabetics is related to changes in blood viscosity.