赤血球膜蛋白への血清脂質とリポ蛋白の関与

Abstract

The impairment of blood fluidity facilitates the formation of ischemic lesion with respect to decrease in blood supply to tissues under the participation of changes in arterial wall and local blood pressure gradient. Functional compensation due to augmentation of blood fluidity for decrease in blood supply to tissues would protect even elderly adults with systemic arteriosclerotic changes from the occurrence of thrombotic diseases. Blood fluidity is influenced by corpuscular and plasma components in the blood. Erythrocytes participate to low blood fluidity by increasing viscosity and decreasing the deformability induced by low stroma ATP content and quality changes in membrane constituents affected by plasma lipids and lipoproteins. This study was intended to clarify fundamental association of serum lipids with erythrocyte membrane proteins as a part of lipid and hemorheological research in thrombotic cerebrovascular disorders.Seventy-nine healthy adults with normal physical findings, blood pressures, urinalysis, blood sedimentation rate, chest films, ECG, liver function tests and serum lipids were selected for this study in the annual screening for circulatory disease. Blood specimens were drawn in the fasting state early in the morning. Erythrocyte membrane was separated by the method of Dodge et al., the membrane proteins were extracted and analyzed qualitatively using SDS-polyacrylamide gel disc electrophoresis by the method of Weber et al., Total cholesterol (TCh), triglyceride and phospholipid were determined by conventional methods, HDL-cholesterol (HDL-Ch) by MgCl2-dextran sulfate method, LDL and VLDL by the precipitating method, and apo A-I, apo A-II and apo B by single radial immunodiffusion method.Subjects aged above 60 years revealed significantly higher levels of TCh, LDL and apo B, and significantly lower levels of HDL-Ch and HDL-Ch/TCh ratio compared with those aged 20 to 39 years. Erythrocyte membrane band 2.1 connecting with spectrin affecting immediately erythrocyte deformobility was lower in subjects aged above 60 years than in those aged 20 to 39 years. In subjects aged 20 to 39 years, serum TCh, esterified Ch and LDL were directly proportional to spectrin 1, spectrin 2 and inversely to glucose 3 phosphate dehydrogenase, and HDL-Ch directly to band 4.1, 4.2, 8 and actin (Table 3). LDL was directly proportional to spectrin (band 1+2) (Fig. 2). In subjects aged 40 to 59 years, apo A-I was inversely proportional to actin, apo A-II directly to band 4.1 (Table 4). In subjects aged above 60 years, A-I was directly proportional to band 2.1 (Fig. 3). Neither of age groups showed significant relationships between serum unesterified Ch and membrane proteins.Erythrocyte lipids are almost located in the membrane. The mature erythrocyte is incapable of the denovo synthesis of cholesterol. A notable feature of blood cholesterol is its ability to exchange between erythrocyte and plasma. Morphological observations have shown the appearance of various kinds of abnormal erythrocyte, which impaires hemorheological behavior following the changes of membrane lipids with regard to the membrane protein and stroma ATP. Although membrane lipids analysis is lacking in our study, intimate associations of serum lipids and lipoproteins with the membrane protein were shown. Therefore serum lipids should be regarded as one of important factors in the development of hemorheological disorders as well as the participation in atherosclerosis in thrombotic disorders.