The Potency of Sensitized Photohemolysis Depends on the Composition of the Reaction Vessel

Delayed photohemolysis has been shown to vary with the composition of the reaction vessel. Human erythrocytes were illuminated in the presence of sensitizer for 1 h and examined 23 h later for percent hemolysis. Four sensitizers, two cationic and two anionic, and three types of reaction vessel were studied. The cationic sensitizers were much more effective in tissue culture treated plastic than in neutral plastic or glass. All were somewhat more effective in neutral plastic than glass. Sorption of sensitizers to reaction vessels without cells present was also studied. In some cases sorption leads to virtually complete removal of sensitizer from the reaction medium. In other cases no sorption is detectable. For the highest sorbing sensitizer total replacement of the reaction medium with sensitizer‐free solution did not decrease effectiveness, demonstrating that sorbed sensitizer is available to sensitize. The results suggest that photooxidation of the cell membrane occurs in two zones, one at the interface between vessel surface and cell surface, and the other where the membrane faces the bulk reaction medium. The relative importance of the interface may depend on the strength of sorption and the affinity of sensitizer for the cell membrane.