Age-Related Changes in Dermal Absorption of 2,3,7,8-Tetrachlorodibenzo-p-dioxin and 2,3,4,7,8-Pentachlorodibenzofuran

Age-Related Changes in Dermal Absorption of 2,3,7,8-Tetrachlorodibenzo-p-dioxinand 2,3,4,7,8-Pentachlorodibenzofuran. BANKS, Y. B., BREWSTER,D. W., AND BIRNBAUM, L. S. (1990). Fundam. Appl. Toxicol. 15,163–173. Changes in the structure and function of agedskin may alter percutaneous absorption of environmental compoundssuch as the halogenated aromatic hydrocarbons. TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin)and 2,3,4,7,8-pentachlorodibenzofuran (4PeCDF) were previouslyfound to be poorly absorbed in 3 month male Fischer 344 ratswithin 3 days after dermal administration. In order to examineage-related changes in dermal absorption and changes in potentialfor systemic exposure, the absorption, distribution, and eliminationof TCDD and 4PeCDF were examined in male Fischer 344 rats ofvarious ages (TCDD: 10, 36, and 96 week; 4PeCDF: 10, 36, 64,96, and 120 week). Each compound was applied at a dose of 0.1µmol/kg and/or 0.04 µmol in 60 µ1 acetoneto a preclipped region of the back and covered with a stainless-steelperforated cap. Rats were housed in individual metabolism cagesfor 3 days. Dermal absorption of both compounds was decreasedin older age groups compared to 10 week rats. The major tissuedepots for both compounds were liver, adipose, skin, and muscleand in comparable age groups, the liver.fat ratio was greaterin 4PeCDF-treated animals. Age-related changes in the distributionof the administered dose and the absorbed dose varied with thecompound as well as the depot. Elimination of TCDD and 4PeCDFwas limited at all ages. Results indicate that percutaneousabsorption of these compounds is decreased in older animals,suggesting that systemic bioavailability may be decreased inolder organisms following dermal exposure to TCDD or 4PeCDF.