Critical windows of vulnerability for effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on prostate and seminal vesicle development in C57BL/6 mice.

A single maternal dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on gestation day (GD) 13 can greatly impair ventral prostate, dorsolateral prostate, anterior prostate, and seminal vesicle development in wild-type C57BL/6 mice. The developmental stages at which these organs are most sensitive to TCDD exposure have now been investigated. Pregnant mice were dosed orally with 5 micro g TCDD/kg or vehicle on GD 13, and their pups were fostered at birth to dams of the same treatment or cross-fostered to dams of the opposite treatment. Additional males had in utero and lactational TCDD exposure following maternal dosing on GD 16. Organ weights and secretory protein, cytokeratin 8, and cyclophilin mRNA expression were determined at 35 days of age. Effects of TCDD on ventral prostate development were due primarily to in utero exposure; the critical window was between GD 13 and birth. Dorsolateral prostate development was inhibited about equally by in utero or lactational exposure, and vulnerability did not begin until GD 16. Anterior prostate development was also affected by both in utero and lactational TCDD exposure, particularly the former. Vulnerability began before GD 16 and continued into postnatal life. Seminal vesicle development was essentially unaffected by in utero or lactational exposure alone but was significantly inhibited by combined exposure, regardless of whether dams were dosed on GD 13 or 16. In summary, the time during which each organ was most vulnerable to TCDD exposure varied from one organ to another. These findings provide insights into the developmental processes that TCDD inhibits in each organ, and demonstrate that TCDD inhibits ventral prostate development before this organ first appears, presumably via effects on the urogenital sinus. The observation that in utero TCDD exposure (alone) inhibited development of each prostate lobe is significant because previous studies have shown that little TCDD is transmitted to mice before birth.