Levels of 3-Methylcholanthrene and 7,12-Dimethylbenz[a]anthracene in Rat Mammary Fat Pads After Intragastric Administration, and Relationships to Carcinogenic Response2

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Abstract
Levels of fluorescence-detectable 3-methylcholanthrene (MCA) and 7,12-dimethylbenzlalanthracene (DMBA) in mammary fat pads after gastric instillation of single and multiple dosages were determined in female and male Wistar and Sprague-Dawley rats. Peak levels for MCA were higher than those for DMBA. Levels in females were higher than in males and higher in inguinal tissue than in axillary tissue. Fluorescence-detectable DMBA disappeared from mammary fat pads more rapidly than MCA. Greatest uptake of MCA occurred with the use of digestible lipid vehicles. Repeated daily doses of MCA did not increase uptake levels beyond those of comparable single administrations. The data do not show any simple relationships between carcinogen levels as measured fluoro-metrically in mammary fat pads and carcinogenic response, but reveal several fruitful directions for further studies in pharmacodynamics and mechanism of action of carcinogens.