2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD): results of a 13-week oral toxicity study in rats.

:2,3,7,8~Tetrachlorodibenzo-p-dioxin (TCDD): Results of a 13-Week Oral Toxicity Study in Rats. KOCIBA, R. J., FEELER, P. A., PARK, C. N. and GEHRING, P. J. (1975). ffoxicol. Appl. Pharmacol. , . Rats were given 2,3,7,8if tetrachlorodibenzo-p-dioxin (TCDD) at dose levels of 0, 0.001, lOffb (06ffb Iffvw \Mr* • ti.Ql, 0.1 or 1.0 pg/kg -S days/week for 13 weeks. Doses of 1.0 vpg TCDD/kg/day caused some mortality, inactivity, decreased Jbody weights and food consumption, icterus, increased serum iilirubin and alkaline phosphatase, pathomorphologic changes • in the liver, lymphoid depletion of the thymus and other ;3,ymphoid organs, increased urinary excretion of porphyrins-and delta-aminolevulinic acid, and minimal alterations of some hematopoietic components. Morphological evidence of a functional ^suppression of the reproductive organs was consistent with either a direct toxicological effect of this dose of TCDD, or an indirect toxicological effect associated with the poor physical condition \t}0ff\> -of these rats. Doses of 0.1 yg TCDD/kg/day caused decreased body ^weights and food consumption, and slight degrees of liver degeneration and lymphoid depletion. Other effects seen only in females given this dose level included increases in urinary excretion of coproporphyrin and delta-aminolevulinic acid and increases in serum -alkaline phosphatase and bilirubin. Effects seen only in males rgiven this dose level included a depression of some hematologic .^parameters (packed cell volume, red blood cells and hemoglobin). Wft \ffi In rats given 0.01 or 0.001 yg TCDD/kg/day, all parameters were ^essentially unaffected, except for a slight increase in the mean lOffi liver-to-body-weight ratio in rats given 0.01 yg TCDD/kg/day. : This slight increase in relative liver weight was not considered vof .any toxicological significance. These data indicate that no Wffk (W\> ; : discernible ill effects occurred in rats given 0.01 or 0.001 yg TCDD/kg 5 days/week for 13 weeks.