Abstract

The phototoxic action of hematoporphyrin in the mouse has been evaluated by a sensitive quantitative technique. Indirect evidence suggests the release of histamine during the early phase of the photodynamic process. Pretreatment with antihistamines, the histamine depleting agent 48/80, and histamine did not alter the lethal phototoxic action of hematoporphyrin in the mouse. Removal of fur increased the sensitivity of black and white mice to lethal hematoporphyrin phototoxicity. The toxic action of hematoporphyrin and light are blocked in the mouse by pretreatment with Evans Blue.