A spin label study of the erythrocyte membrane in mothers and sisters of patients suffering from Duchenne muscular dystrophy.

The erythrocyte membranes of mothers and sisters of boys suffering from Duchenne Muscular Dystrophy (DMD) have been studied by spin labelling. Two oxazolidine nitroxide derivatives of stearic acid were used. With the first of them (16 NS) which probes the hydrophobic part of the phospholipids, we measured the fluidity of the membrane as a function of temperature. The second nitroxide derivative (5 NS) probes the membrane near the phospholipid polar heads. The amplitude of the electron spin resonance signal was studied as a function of the spectrometer microwave power in order to determine the paramagnetic label saturation behaviour. No significant difference was observed between the control adult women and the carrier mothers. On the contrary, almost all the normal young premenarchial girls showed simultaneously a break in the fluidity vs. temperature plot of the 16 NS probe and a saturation phenomenon of the 5 NS label signal. In about 50% of the DMD boys' sisters, no break in the temperature plot nor saturation behaviour was observed. This corresponds to the theoretical repartition between normal and carrier girls if one admits that about 30% of the latter do not have any detectable membrane abnormality, as in the case of the creatine kinase (CK) test which shows about 30% of normal levels in carrier women. The study of the erythrocyte membrane in young girls can then be an useful complementary tool to detect DMD carriers.