2,3,7,8-Tetrachlorodibenzo-p-dioxin ŽTCDD. in toluene ŽChemsyn Science Laboratories, Lenexa, KA, USA. was used. The solvent was removed under a stream of nitrogen and sterile corn oil was added to the appropriate concentration. Each mouse received 0.2 ml of this solution, corre- sponding to a dose of 500 ng TCDD