Erythrocyte membrane composition in patients with primary hypercholesterolemia

There are conflicting results regarding the erythrocyte membrane cholesterol and phospholipid content in patients with primary hypercholesterolemia (PHC), due to methodological problems in obtaining haemoglobin-free ghosts. At the same time, the different units used and the fact that the cholesterol and phospholipids are not expressed in relation with integral protein membrane content, produces contradictory results. We have analysed in 33 patients with PHC (12 males, 31 females) aged 43 +/- 12 years and in 33 healthy normolipaemic volunteers (9 males, 24 females) aged 43 +/- 13 years plasma lipids, along with, erythrocyte membrane cholesterol, phospholipids and integral proteins. PHC patients showed increased erythrocyte membrane cholesterol: 0.36 +/- 0.15 mg/mg when compared with controls: 0.29 +/- 0.75 mg/mg; p = 0.018. Phospholipid membrane content, although higher in the cases, did not reach statistical significance (PHC patients: 0.38 +/- 0.15 mg/mg vs. 0.33 +/- 0.72 mg/mg; p = 0.098). The cholesterol/phospholipids ratio (Chol/Ph) was 0.99 +/- 0.22 in PHC patients versus 0.92 +/- 0.28 in controls; p = 0.127. Our results suggest that there is a slight increase in erythrocyte membrane cholesterol in patients with PHC. Given the increasing importance of erythrocyte membrane cholesterol in the stability of the atheroma plaque due its possible contribution to the clinical signs of ischaemic heart disease, it seems relevant to determine this parameter in risk populations. Therefore, a simple and reproducible method needs to be standardised which would enable comparisons between laboratories and facilitate further studies aimed to it as a marker of acute coronary syndromes.