Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the lactating rat on maternal and neonatal vitamin A status.

Female Sprague-Dawley rats were given a single oral dose of 10 micrograms TCDD/kg body wt after delivery. Pups were killed on postnatal day (PND) 0, 2, 4, 8, or 16. Dams and remaining weanlings were killed on PND 22 and 32, respectively. Thymus weight was lower in dams exposed to TCDD than in controls, whereas no differences in body weight or relative liver weight were found. The total amount and the concentration of vitamin A were lower in the liver but higher in the kidneys and in serum of TCDD-treated dams than in controls. TCDD-exposed weanlings showed lower weight gain, liver enlargement and thymus atrophy compared to controls. Growth reduction became more pronounced with time, liver enlargement was at its peak on PND 8 and thymus atrophy was most pronounced on PND 16, although all three effects persisted throughout the study. The total amount of vitamin A increased at a similar rate in control and TCDD-exposed weanlings throughout lactation. When the young started to eat pelleted diet there was a pronounced increase in hepatic vitamin A content. Between PND 16 and 32 controls increased their hepatic vitamin A content 21-fold, compared to 12-fold in TCDD-exposed offspring. The hepatic stores of TCDD-treated animals reached 45% of the stores of control pups on PND 32. From PND 8 renal vitamin A was significantly higher in the TCDD-exposed young than in the controls. At PND 32 TCDD-exposed weanlings had six times more renal vitamin A than controls.