Impairment of the erythrocyte membrane fluidity in survivors of acute myocardial infarction. A prospective study

Erythrocytes have to constantly adapt themselves to the varying circulatory system shear stress forces and capillaries diameter. Membrane lipid and pr otein content have an important role in determining the erythrocyte shape a nd are main determinants of the membrane solid and fluid behaviour which en ables the erythrocyte to respond to the outer environment modifications. Me mbrane fluidity is an inverse index of membrane microviscosity. The aim of the present work is to evaluate prospectively in three periods of time (dis charge, after 6 months and one year later) in survivors of an acute myocard ial infarction (AMI) the erythrocyte membrane fluidity (outer and inner bil ayer) and establish a relation with the cardiovascular events or need of co ronary revascularization during a two year clinical follow up. Sixty survivors of acute myocardial infarction were recruited during 1994-9 6 and were prospectively studied in three periods (discharge, 6 months and after one year), and were compared with a control group (n = 36). Membrane lipid fluidity was determined by means of fluorescence polarisation with tw o probes: 1,6-diphenyl-1,2,5-hexatriene (DPH) and 1,4-trimethylamine 6-phen yl hexa-1,3,5-triene (TMA-DPH), for the characterisation of the hydrophobic and external polar region, respectively. The hydrophobic region was more rigidified (p < 0.01) in the erythrocytes f rom AMI patients, in relation to the control group. During the time of the study there was a progressive erythrocyte membrane rigidification (DPH p < 0.001; TMA-DPH p < 0.001). We found no relation between erythrocyte membran e fluidity and the coronary risk factors, cardiovascular events or the need of coronary revascularization during the clinical follow-up. In conclusion, after the myocardial infarction erythrocyte membrane of AMI survivors becomes more rigid with time, which could contribute to the decre ased erythrocyte deformability and the increased blood viscosity previously described in this group of patients.