Electron spin resonance spin label studies of the erythrocyte membrane in Duchenne muscular dystrophy

Effects of intramembrane particle aggregation on erythrocyte membrane fluidity: an electron spin resonance study in normal and in dystrophic subjects

Mobilization and aggregation of intramembrane particles (IMPs) are physiological events observed in various cells. In erythrocyte membranes, aggregation of IMPs can be induced by the exposure of partially desprectrinized erythrocyte membranes to acidic pH. We investigated the association between IMPs aggregation, protein mobility, and membrane fluidity in erythrocyte membranes of healthy controls and Duchenne muscular dystrophy (DMD) patients by using electron spin resonance and specific spin labels for membrane proteins and lipids. In erythrocyte membranes of control subjects, the partial spectrin removal induced a decreased segmental motion of protein spin label indicating an increase of protein-protein interactions. Stearic acid spin labels 5- and 16-(N-oxyl-4,4'-dimethyloxazolidine) showed that the treatment induces an increase of membrane fluidity. In DMD patients, both treated and untreated erythrocyte membranes showed changes of membrane fluidity when compared to those of the controls. Our results suggest that defects in the interactions between skeletal proteins and/or between membrane and skeleton components may contribute to the alterations of erythrocyte membranes in DMD.

Studies of water permeability and proteins of erythrocyte membranes in patients with Duchenne muscular dystrophy

The characteristics of water permeability of erythrocytes from 54 Duchenne muscular dystrophy (DMD) patients and age-matched controls have been determined by a pulse nuclear magnetic resonance (NMR) technique. A decreased permeability of erythrocyte membrane in DMD was definitely found at all temperatures between 15 and 42 degrees C, with normal values for the activation energy of water diffusion. No differences between DMD and control subjects in the pattern of erythrocyte membrane polypeptides separated by two-dimensional electrophoresis could be detected. The findings are discussed in relation to the molecular mechanisms of water diffusion across erythrocyte membrane and the problem of erythrocyte membrane abnormalities in DMD. A new interpretation of erythrocyte membrane alterations is proposed based on the recent findings regarding the molecular pathology of DMD.

5'-Nucleotidase in skin fibroblasts from patients with Duchenne muscular dystrophy

The 5'-nucleotidase of plasma membranes of cultured skin fibroblasts from patients with Duchenne muscular dystrophy had a reduced affinity for its substrate, 5'-AMP. The Arrhenius plot of the temperature dependence of this enzyme activity was normal. There was no difference between patients and controls in the specific 5'-nucleotidase activity in the whole cell homogenates.

Some biophysical properties of the erythrocyte membrane in Duchenne muscular dystrophy

Inasmuch as prior authors have suggested a 'generalized membrane defect' in patients with Duchenne muscular dystrophy, this study was undertaken to examine some biophysical properties of the erythrocytes in affected individuals. Using the micropipette technique we investigated the rheological properties of erythrocytes from 11 Duchenne muscular dystrophy patients (boys 3-14 years old) and 5 carriers (mothers 20-42 years old). The mean elastic modulus and membrane viscosity of the patient's erythrocytes were not significantly different from those of a group of 8 unaffected age-matched boys. The carrier group did not differ significantly from the adult control group in any of the rheological parameters. A significant increase in the number of stomatocytes was observed in the patient group, and a similar trend (not statistically significant) was observed in the carrier group. The membrane lipid fluidity of erythrocytes from patients, carriers, and normal controls was assessed with three different probes by fluorescence depolarization, and no significant differences were found. Our results indicate that there is a progressive elevation of the membrane elastic modulus with increasing age of the patients: the younger patients have a lower elastic modulus than their age-matched controls, while the older patients have a higher elastic modulus than their age-matched controls.