ISSN:
1435-604X
Keywords:
Erythrocyte membranes
;
Hemolysis
;
Photosensitising agent
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
,
Physics
,
Technology
Notes:
Abstract Photosensitised haemolysis of red blood cells (RBC) by sodium hypericin, haematoporphyrin, protoporphyrin, Photofrin® and benzoporphyrin derivative monoacid ring A were investigated for broad spectrum near-ultraviolet (UVA)-visible light and monochromatic 630 nm irradiations. The delayed photohaemolysis rate (1/t 50) increased with the approximate square of the incident light dose, wheret 50 is the dark incubation time required for 50% haemolysis. The power dependence of 1/t 50 on the sensitiser concentration varied with the specific sensitiser and the irradiation conditions. Energy calculations for protoporphyrin show that the quantum efficiency of delayed photohaemolysis at 630 run is independent of the sensitiser concentration at constantt 50 and increases witht 50 The protective effects of water-soluble singlet oxygen quenchers are indicative of a Type II photosensitisation pathway for these agents. Pretreatment of RBC with hydrogen peroxide suppressed photosensitisation by protoporphyrin accompanied by lipid peroxidation and oxidation of haemoglobin. The photohaemolysis curves are analysed with a target theory model which postulates that haemolysis requires thermal activation of photochemical damage. The model calculations indicate that photosensitised haemolysis requires two photochemical hits and a highly cooperative thermal process.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00592959
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