fa Morphometry Morphometry Original Original <strong>Purpose</strong>: The aim of this study was to evaluate the effect of age on the capacity of liver and epiderm of adult and weanging rats in transformation of Benzo (&alpha;) Pyrene.<br> <strong>Materials and Methods</strong>: In a metabolic activiation assay system, cytochorome P-50 (from microsomal fraction) catalyses the formation of reactive epoxide of BaP which can then interact with exogenous DNA The capacity of cytochrome P-450 for B&alpha;P-DNA adducts formation from different organs are adult rat live>>> adult rat skin>> weanging rat liver> weanling rat skin. With the addition of cytosol (the source of glutathione S transferase (GST) to the microsome-mediated system an In vitro detoxification model has been established.<br> <strong>Results</strong>: The results obtained by the addition of different cytosolic samples are shown in several tables in the text. These data show that isolation of subcellular fractions from young rats are less efficient in the biotransformation of B&alpha;P and detoxification by GSH is a passive process that depends on activation process. Also metabolic activation of BaP with cytochorome P-450 is not the first degree with glutathione detoxification. However, the results obtined In vitro do not reflect the exact change In vivo. Benzo (Α) pyrene, Dna, Glutathione, Rat 53 62 http://anatomyjournal.ir/browse.php?a_code=A-10-304-36&slc_lang=fa&sid=1 Mostafa Mohammadi 10031947532846006727 10031947532846006727 Yes Biochemistry and Microbiology Departmen, Islamic Azad University, Flavarjan, Iran. Abdol Amir Allameh 10031947532846006728 10031947532846006728 No Mohammad Hassan Asadi Sar Yazdi 10031947532846006729 10031947532846006729 No Mohammad Reza KHhajeh 10031947532846006730 10031947532846006730 No