Histopathological and Ultrastructural Studies of Liver Tissue from TCDD-Exposed Beach Mice (Peromyscus polionotus)

Quantitative ultrastructural studies were conducted on liver tissue from beach mice, Peromyscus polionotus, exposed to the toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in field and laboratory environments. Hepatic tissue from 52 animals was examined for changes in smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER), and mitochondria. Fifteen of 30 animals were collected from a unique military test site in northwest Florida where they had been continuously exposed to soil levels of 10 to 710 parts per trillion (ppt) TCDD. Twelve of 22 animals were exposed 10 times in 28 days to 2.5 parts per billion (ppb)TCDD applied as a dust to their pellage. All remaining animals were from either a field control site or not exposed to TCDD in the laboratory. All tissue was examined both histopathologically and by an ultrastructural stereological technique. No significant histopathological or ultrastructural changes were found in hepatic parenchymal cells after long term, low level exposure to TCDD in the field, or after short term, low level exposure in the laboratory. Statistically significant differences in liver weight to body weight ratios concurrent with the absence of cellular changes following exposure to TCDD in the field is explained by the low level of exposure.