Experimental Investigation

Kinetic Model of Photosensitized Homolysis of Erythrocytes: Multihit Target Theory

  • Mehmet Dinçer BILGIN
  • A. Eser ELÇIN

Received Date: 22.04.2004 Accepted Date: 20.12.2004 Meandros Med Dent J 2004;5(3):5-9

Aim: By using rate kinetics of photosensitized hemolysis of erythrocyte as a model system, understanding themechanism of photosensitization on the cell membrane was purposed in this work. Photohemolysis required the combined effect of the light activated (photochemical stage) and thermal (thermal stage) process, and these stages can be represented by “Multihit Target Theory”, defined with photochemical and thermal hit numbers. Method: Photohemolysis rate was calculated by using 1/t = g Lk C j where t is the dark incubation time required for 50% hemolysis, L is the incident light dose, Cs is the bound dye concentration, j and k are the “as measured” exponents, and g is the reaction constant. Erythrocyte suspension, which was prepared in pH 7.4 10 mM phosphate buffered saline, was photosensitized with various concentration of protoporphyrin IX and was irradiated by visible light. Then, delayed photohemolysis was measured for each sample, and data were analyzed using “Multihit Target Theory”. Results: Prolonged  t50    values  were  measured  on  delayed  photohemolysis  curve  (s-shaped)  with  lowprotoporphyrin IX concentration and irradiation time. Delayed photohemolysis measurements are indicative of second power dependence of the photohemolysis rate on the absorbed light energy. Photohemolysis data obtained from experiments and kinetic model calculations were in good agreement. Conclusion: “Multihit Target Theory” is important for characterizing and comparing photohemolysis results. The effects of various concentrations of photosensitizers and light doses on photohemolysis curve were analyzed with kinetic model. Thus, experimental data were in good agreement with recent kinetic model, based on “Multihit Target Theory”.

Keywords: “Multihit Target Theory”, erythrocyte membrane, photohemolysis, kinetic model, protoporphyrin IX