Light & electron microscopy of proliferating oval cells during early chemical hepatocarcinogenesis

Early hepatic changes were studied in male albino rats (70) of Sprague Dawley strain fed a choline devoid diet containing 0.05 per cent w/w AAF (2-acetylaminofluorene) for 12 days. Proliferating periductal and ductal cells appeared in the portal area on days 1 and 3 respectively in the experimental group. On day 7, these cells infiltrated within the sinusoids of adjacent lobules up to the first one or two layers of hepatocytes. Subsequently, these cells extended up to the midzonal region on day 21 and by day 24 the entire lobule was infiltrated. Formation of duct like structures by the proliferating cells was seen on day 21. Ultrastructurally both periductal and ductal cells showed only a few organelles. Periductal and ductal cells are the earliest cells to appear in the portal area in chemically induced hepatocarcinogenesis. Its undifferentiated ultrastructure, may suggest the stem cell nature of these cells.