Safety evaluation of certain food additives - ipcs inchem

ALKOXY-SUBSTITUTED ALLYLBENZENES 399
3/5 mice at 75 weeks. All hepatocellular carcinomas proliferated when transplanted
into syngeneic hosts. Thus, results demonstrated a sequential development of
altered hepatocyte populations leading to hepatocellular carcinomas in safroletreated
mice (Lipsky et al., 1981a).
Livers of mice in the above study were weighed and subjected to enzyme
histochemistry (Lipsky et al., 1981b). At week 8, liver centrilobular tissue showed
decreased glucose-6-phosphatase and SDH activities. Foci of enzyme-altered
hepatocytes noted at 24 weeks and thereafter contained cells showing decreased
glucose-6-phosphatase and SDH activities and increased gamma-glutamyl
transpeptidase (GGT) activity. In control, iron-loaded mice, livers were intensely
siderotic. In safrole-exposed, iron-loaded mice, foci of hepatocytes resistant to iron
accumulation, varying from a few cells to a lobule in diameter, were initially noted
at 24 weeks. After 36–75 weeks of safrole treatment, hepatocellular adenomas were
noted with altered enzyme histochemical profiles. Hepatocytes from adenomas
were characterized by a decreased staining for glucose-6-phosphatase and SDH
and by increased staining for GGT and glucose-6-phosphate dehydrogenase. A few
nodules showed a decrease in staining for 5-nucleotidase. In iron-loaded mice,
hepatocytes of adenomas showed decreases in levels of stainable iron when the
surrounding parenchyma was siderotic. Hepatocellular carcinomas occurred in
livers of mice exposed to safrole for 52–75 weeks. Cells of hepatocellular
carcinomas displayed decreases in glucose-6-phosphatase and SDH activities and
increases in GGT and glucose-6-phosphate dehydrogenase activities. In ironloaded
mice, the hepatocellular carcinoma cells were negative for stainable iron.
Foci, adenomas and hepatocellular carcinomas displayed some variability in
enzyme histochemical reactions, and variability existed between lesions as well as
between cells of the same lesion.
An ultrastructural analysis was performed on safrole-induced hepatocellular
adenomas and hepatocellular carcinomas in mice. Adenomas were heterogeneous
in cell composition and contained dark-staining basophilic cells, pale-staining
acidophilic cells, clear cells and lipid-laden cells. Darkly staining cells resembled
fetal hepatocytes. They had large nuclei with irregular borders and limited diversity
of organelles. Rough endoplasmic reticulum was prominent and was observed as
parallel cisternae in single or double tracts, which are often associated with
mitochondria. Pale staining cells contained abundant smooth endoplasmic
reticulum. Other organelles were often displaced to perinuclear or peripheral
regions of the cell. Clear cells contained large areas of glycogen deposition. Lipidladen
cells contained numerous, variably sized lipid droplets in the cytoplasm.
Hepatocellular carcinomas contained cell types similar to those of adenoma. They
contained many anaplastic cells. These resembled hepatocytes but contained
several other alterations. The cytoplasm was often filled with enlarged mitochondria
with dense or pale matrices. The cristae were sparse and had altered configurations.
Microbodies increased in number and often clustered in one region. Increases
were seen in the number of microbodies that were noted in other cells of
hepatocellular carcinomas. The results demonstrate similarities between adenomas
and hepatocellular carcinomas, but anaplastic cell types were a feature only of
carcinomas. Owing to the similarity of cell types, adenoma could be considered a
possible site of hepatocellular carcinoma development (Lipsky et al., 1981c).