Membrane fluidity of nonmuscle cells in Duchenne muscular dystrophy: effect on lymphocyte membranes of incubation in patient and control sera.

Abstract

The membrane fluidity of intact fibroblasts, erythrocyte ghosts, and intact lymphocytes from Duchenne muscular dystrophy (DMD) patients and controls was measured by steady state fluorescence polarization. The fluorescent probes used were diphenylhexatriene (DPH), trimethylammonium-DPH, and a set of n-(9-anthroyloxy) fatty acids. Fluorescence anisotropies in DMD fibroblasts and DMD erythrocyte ghosts were normal. In DMD lymphocytes (n = 10) fluorescence anisotropy of DPH was decreased versus controls (0.212 +/- 0.028 versus 0.231 +/- 0.012, p less than 0.05). Linear regression analysis of creatine kinase activity in sera and DPH fluorescence anisotropy in lymphocytes from DMD patients showed a negative correlation (r = -0.93, p less than 0.001). DMD lymphocytes and control lymphocytes were incubated for 4 h in sera from DMD patients and from controls. When incubated in DMD sera, DPH fluorescence anisotropy of DMD lymphocytes decreased from 0.211 +/- 0.018 to 0.180 +/- 0.028, and fluorescence anisotropy of control lymphocytes decreased from 0.239 +/- 0.012 to 0.179 +/- 0.025 reaching the same level as did DMD lymphocytes. When incubated in control sera, DPH fluorescence anisotropy of DMD lymphocytes increased to 0.224 +/- 0.012, and fluorescence anisotropy of control lymphocytes decreased to 0.218 +/- 0.017. The fluorescence anisotropy changes after incubation in DMD versus control sera were different (p less than 0.05 for DMD lymphocytes and p less than 0.005 for control cells). Our findings do not support the hypothesis of a general membrane defect but suggest a toxic serum factor in DMD which attacks lymphocyte membranes and possibly muscle membranes at the same time.