Abstract |
Maturational changes in potential for systemic exposure to TCDD following dermal application of a low dose (200 pmol) of this chemical were examined in male Fischer 344 rats. Absorption, tissue distribution, and elimination of TCDD, measured as TCDD-derived radioactivity, were examined 72 hr after dermal application of 200 pmol ((3)H)TCDD (111 pmol/sq cm applied over 1.8 sq cm) to the interscapular region of 3-, 5-, 8-, 10-, and 36-week-old rats. Dermal absorption was greatest in 3-week-old rats, decreasing to approximately 80 pmol (approximately 40%) in 5-, 8-, and 10-week-old rats and to 45 pmol (approximately 22%) in 36-week-old rats. In each age group, 70 to 80% of the radioactivity remaining at the application site 72 hr after dosing could be removed with acetone swabs. Major tissue depots of radioactivity were liver and fat; skin and muscle were minor depots. Adipose tissue content (Y) increased linearly with body weight. (X),Y = 0.03X + 2.1 (R squared = 0.95). Results indicate that TCDD is absorbed to a greater degree through skin of very young animals and that a significant decrease in potential for systemic exposure may occur during maturation and again during aging. |