We propose to investigate the influence of the amount and degree of unsaturation of dietary fat on tumor production by carcinogens, and how the presence or absence of antioxidant in these same diets affects the tumor incidence. Preliminary studies (see page 33) indicate that the inhibitory effect of antioxidants on chemical carcinogensis promoted by dietary fat may be related to the property of antioxidants for inhibiting peroxidation of unsaturated fat. The studies in this project are designed to probe these interrelationships more deeply. The preliminary studies will be repeated for confirmation, testing several antioxidants and carcinogens. It will then be determined if consumption of dietary antioxidant is required only for a short time before, during or after treatment with a carcinogen, or if long-term maintenance of the animals on the antioxidant-containing diet is required to insure reduced tumor incidence. In addition, we will investigate the effect of feeding the various diets on the capacity of microsomes to form mutagenic compounds in vitro from the carcinogens to be studied, since modulation of the system which metabolizes carcinogens may be induced by the different diets. We will also investigate the metabolism of the carcinogens by primary liver cell cultures and microsomes from animals on the different diets for evidence of production of reactive carcinogen free radicals, utilizing the electron spin resonance (E.S.R.) spin-trapping technique we have developed in this laboratory for detecting enzyme-generated radicals. An investigation is planned to determine the capacity of certain carcinogens to initiate lipid peroxidation in microsomes and primary liver cell cultures from animals fed the different diets to determine if this property can be related to the metabolism of the carcinogen to free radical forms and to the inhibitory effect of antioxidants on tumorigenesis. Finally, we will study the distribution and time of retention of 14C-labeled carcinogens in various tissues of animals fed the different diets with and without antioxidants. We will determine the fraction of the 14C-label in selected tissues which is acetone-soluble and acetone-insoluble.