An Exploratory Investigation on the Inhibition of Selected Photosensitizers by Agents of Varying Antioxidant Activity

Abstract

The interactions between 25 selected antioxidants and 4 photosensitizing agents have been investigated over a wide concentration range at log-fold increments, using a previously established in vivo bioassay for antioxidants based on their ability to protect Tetrahymena pyriformis against the oxygen-dependent effects of photodynamic toxicity. These data have been topologically characterized by families of contours of constant response (isobols), the importance of whose general pattern, rather than whose individual locations and slopes, is stressed. Protective effects, in general, increase progressively with increasing antioxidant concentrations and with decreasing photosensitlzer concentrations; they are similar for a given antioxidant, irrespective of which photosensitizer it is tested against. Antioxidant and photosensitizer dose-response slopes are a function of the width of horizontal and vertical separations, respectively, between adjacent isobols. No characteristic isobol pattern is seen for primary or secondary antioxidants, or for antioxiants within a particular group, such as the "hindered" phenols or amines.