SPONTANEOUS OCCURRENCE OF PLACENTAL GLUTATHIONE S‐TRANSFERASE‐POSITIVE FOCI IN THE LIVERS OF LEC RATS

Spontaneous occurrence of placental glutathione S‐transferase (GST‐P)‐positive foci was observed in the livers of 5‐month‐old LEC rats. Quantitative studies revealed that GST‐P foci appeared after the onset of hepatitis. The number and size of GST‐P foci increased with age and more foci were induced in males than in females. No sex difference, however, was found in the incidence of hepatitis. Although hepatitis is necessary for the induction of GST‐P foci, it is insufficient for their further growth. Since hereditary hepatitis first appears at around 4 months of age, leading to a high incidence of hepatocellular carcinomas in later life, the spontaneous occurrence of the foci may be related to the development of hepatocellular carcinoma.