Photodynamic Modification of Erythrocyte Membrane Proteins Induced by Protoporphyrin
Protoporphyrin is accumulated in the erythrocytes of patients with erythropoietic protoporphyria (EPP) as the result of decreased hemesynthetase activity after disappearance of the nucleus from the erythroid cell (3). Irradiation of the erythrocytes with visible light causes an increase in cation permeability, ultimately resulting in hemolysis. Photohemolysis can also be evoked by irradiating normal erythrocytes in the presence of protoporphyrin (11). Illumination under nitrogen does not cause hemolysis. It is apparently a photooxidative process. B-carotene protects against hemolysis (11) and with several patients, against skin damage (1). Photosensitized peroxidation of unsaturated fatty acids and cholesterol is not the primary cause of membrane damage (4). Analysis of membrane proteins by sodiumdodecylsulphate-polyacrylamide-gel electrophoresis showed extensive cross-linking of the proteins (5). Since the formation of these crosslinks seemed to be of crucial importance in understanding the photochemical damage, they are studied in more detail, together with some functional aspects of the proteins involved.
KeywordsErythrocyte Membrane Void Volume Fraction Photodynamic Effect Cation Permeability Normal Erythrocyte
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