Localization of ultrastructural alterations induced in rat liver by dietary polybromobiphenyls (FireMaster BP-6)

Abstract

In 1973 and 1974, widespread environmental pollution and animal losses in Michigan were caused by the accidental incorporation of polybrominated biphenyls (PBBs, FireMaster FF-1) in livestock feed. This study documents the deleterious changes in the liver during an early state of polybrominated biphenyl-induced toxicosis. Male weanling Fischer rats were fed diets containing either 0 or 100 ppm of polybromobiphenyls (Fire-Master BP-6) (PBBs) for 10 days. Dietary PBBs did not affect body weight or food consumption. At necropsy, the liver was removed and processed for light and electron microscopy. The livers of PBB-treated rats were enlarged and friable. Light microscopic changes included moderate enlargement of centrilobular and midzonal hepatocytes which exhibited a foamy cytoplasm. Periportal hepatocytes appeared normal except that most bile canaliculi were dilated. Ultrastructural alterations within centrilobular hepatocytes consisted of small and dense mitochondria, abundant smooth endoplasmic reticulum, deep stacks of rough endoplasmic reticulum which appeared disorganized with fewer attached ribosomes, numerous lipid droplets, and dilated bile canaliculi which often contained myelin-like figures. The ultrastructural changes within mid-zonal hepatocytes were similar to centrilobular hepatocytes except there was less proliferation of smooth and rough endoplasmic reticulum, larger and less dense mitochondria, and more numerous lipid droplets which varied greatly in size. Glycogen depletion was apparent in both centrilobular and midzonal hepatocytes as was numerous multi-vesicular bodies associated with the Golgi apparatus.