Lysis of resealed erythrocyte ghosts by photoactivated tetrapyrroles: estimation of photolesion dimensions.
1. Resealed erythrocyte ghosts containing Na+ and glucose-6-P (G6P) as markers of membrane integrity were used as a model system for probing the damaging effects of photoactivated tetrapyrroles on cell membranes. 2. Continuous blue-light irradiation of bilirubin (BR)-sensitized and protoporphyrin (PP)-sensitized ghosts made them progressively more permeable to Na+, the cation emerging well ahead of G6P. 3. G6P efflux occurred abruptly after a lag period and resembled an all-or-none process. 4. These and other results suggest that a relatively subtle structural modification (possibly in some crucial protein(s) is sufficient for Na+ release, whereas gross disruption of the bilayer (probably by free-radical lipid peroxidation) is necessary for G6P release. 5. The dimensions of the G6P-releasing photolesions were estimated by density floatation centrifugation, using saccharides of increasing molecular size. Both BR and PP produced pores greater than 11 A but less than 42 A in diam., which is considerable smaller than the size range estimated in hypotonically lysed ghosts.
D002463:Cell Membrane Permeability / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000187:drug effects*; D004912:Erythrocytes / Q000187:drug effects*; D005958:Glucosephosphates / Q000097:blood; D006461:Hemolysis; D006801:Humans; D010777:Photochemistry; D011758:Pyrroles / Q000494:pharmacology*; D012964:Sodium / Q000097:blood; D045725:Tetrapyrroles
D005958:Glucosephosphates; D011758:Pyrroles; D045725:Tetrapyrroles; D012964:Sodium