Effects of calcium on phthalocyanine sensitized photohemolysis

Influence of divalent Ca2+ ions in sulphonated chlorophthalocyanine (ClAlPcS2) induced photohemolysis in rabbit red blood cells has been investigated. Loading of excess Ca2+ to ClAlPcS2 sensitized RBC suspension enhanced hemolysis in a concentration dependent manner. Protein kinase C (PKC) inhibitor chlorpromazine and cation chelator EDTA reduced Ca2+ enhanced photohemolysis. Photohemolysis increased with calcium channel blockers diltiazem and nifidipine. Enhancement in photohemolysis by Ca2+ ions can arise either by its ability to liberate Fe2+ bound to phosphatidylserine or by stimulation of PKC. Inability of calcium channel blockers to prevent Ca2+ influx following photodynamic treatment of red blood cells suggest nonspecific leakage rather than involvement of Ca2+ channels in erythrocytes.