Salmonella typhimurium TA1538 has been used as an analytical tool to quantify the ability of tissue homogenate supernatants to activate the carcinogen N-2-fluorenylacetamide (FAA) and the proximate carcinogen N-hydroxy-2-fluorenylacetamide (N-OH-FAA). Tissue homogenate supernatants were obtained from male Sprague-Dawley rats fed a basal diet supplemented with 5 or 20% beef tallow or corn oil for 6 months and given i.p. injections of FAA (10 mg/100 g body weight) or of the control vehicle.

After only 21 days of feeding and 1 injection of FAA or control, elevated activity of the liver microsomal-free supernatant (S-150) enzyme that converts N-OH-FAA to mutagen was dependent upon the kind and level of dietary fat. Enzyme activity from FAA-treated rats fed 5% corn oil was 3-fold higher than it was in FAA-treated animals fed 5% tallow, whereas in FAA-treated animals fed 20% corn oil enzyme, activity was 2-fold higher than it was in rats fed 20% tallow.

After 6 months of feeding and 7 i.p. injections of FAA or control vehicle, the mutagen-producing potential of the liver S-150 was increased, regardless of the diet. However, FAA injections plus 20% corn oil or beef tallow promoted the greatest enzyme activity, suggesting a synergistic effect of high fat and FAA. The ability of S-150 to activate potentially mutagenic compounds was 22-fold higher in FAA-treated rats fed 20% corn oil than in FAA-treated animals fed 20% beef tallow. Between 21 days and 6 months, hepatic enzyme activity increased 2-fold for rats fed 5% beef tallow or corn oil, 5-fold for rats fed 20% beef tallow, and 52-fold for animals fed 20% corn oil.

Lung and kidney S-150 enzyme activities were assayed with the bacterial system after 6 months. Dietary fat did not affect the activity of the lung, and although kidney enzyme activity was increased from 1- to 3-fold it was less responsive to diet than liver.

After 21 days and 1 FAA injection, rats had a greater concentration of urinary N-OH-FAA glucuronide when fed corn oil than when fed tallow. After 6 months, the urine of rats fed 20% corn oil and given 7 injections of FAA exhibited the greatest amount of urinary N-OH-FAA.

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Supported in part by a Grant-in-aid from Continental Oil Company to Charies R. Shaw, the Research Institute of Mechanisms of Carcinogen Action, the Research Institute of Food Science and Nutrition at Texas Tech University, and Eli Lilly and Co.

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