PORPHYRIN-INDUCED PHOTODAMAGE TO ISOLATED HUMAN NEUTROPHILS

Abstract— Human neutrophils were irradiated with light at 340–380 nm in the presence of low concentrations of protoporphyrin or uroporphyrin. At increasing light doses or increasing concentrations of protoporphyrin, the neutrophils rapidly lost the ability of locomotion. Also, neutrophil chemiluminescence and hexose-monophosphate shunt activity rapidly declined. An early event was leakage of endogenous K⁺ followed by lactate dehydrogenase and at a later stage leakage of particle-bound acid phosphatase. A number of cellular enzymes were inactivated, the susceptibility to inactivation decreased in the order: succinate dehydrogenase > lactate dehydrogenase > glutamate dehydrogenase > acid phosphatase. Uroporphyrin had no effect on neutrophil functions, leakage of K⁺, or cellular enzymes. The results suggest that photodamage to the plasma membrane and the mitochondria are earlier events than photodamage to lysosomes.