Summary
The function of the red blood cell glucose transporter was compared in samples from
subjects with and without diabetes. Activity of the glucose transporting protein (GLUT-1)
was measured by determining the first order rate constant for uptake of sorbose, a
sugar transported by GLUT-1. Red cells were isolated from 13 patients with diabetes
and 9 patients without diabetes and were washed free of intracellular glucose. The
uptake rate constant was calculated from measurements of sorbose uptake at 0, 1, 2,
5 and 90 minutes at 37°C. The rate constant was significantly decreased in cells isolated
from patients with diabetes (0.242 vs 0.303 min-1 in non-diabetic subjects, p < 0.005). The number of GLUT-1 present per mg of membrane
protein and clinical parameters such as weight, age, serum cholesterol and urea nitrogen
were not significantly different between the groups. The rate constant per pmol of
GLUT-1 was significantly decreased in the diabetic subjects. The relationship between
diabetes control and the rate constant was not linear and there was no relationship
between the calculated intrinsic activity and the HAlc. Because red cell GLUT-1 are
not translocated and red cells do not synthesize new proteins, these data suggest
that the intrinsic function of the glucose transporter from red cells of patients
with diabetes is diminished. This may be due to alterations in the transporter or
its membrane environment.
Key words
Sugar Transport - Sorbose - Erythrocyte Membrane - Glucose Transporter - Diabetes
