Nonenzymatic protein glycosylation. I. Lowered erythrocyte membrane fluidity in juvenile diabetes

In order to determine the fluidity of erythrocyte membrane ghosts the degree of random orientation of excited diphenylhexatriene molecules (anisotropy) was examined in normal and diabetic juveniles. A small but significant enhancement of diphenylhexatriene anisotropy was observed in diabetic erythrocyte membranes when compared with control (0.184 +/- 0.013 versus 0.152 +/- 0.010). This alteration was accompanied by an increase of nonenzymatic glycosylation of membrane proteins and haemoglobin in diabetic subjects (25.7 +/- 2.6 versus 21.1 +/- 2.2 and 7.1 +/- 1.4 versus 4.0 +/- 1.0 respectively). Moreover, elevated plasma glycaemia in diabetes was correlated with an increase in membrane anisotropy in the erythrocyte membranes of diabetic juveniles. Linear relationships were seen between glycosylated hemoglobin and glycosylated membrane proteins (r = 0.767) as well as between glycosylated haemoglobin and membrane anisotropy (r = 0.741). We suggest that membrane protein glycosylation enhancement occurring in diabetes could be one of the reasons of the lowered diabetic erythrocyte membrane fluidity.