SEQUENTIAL QUANTITATIVE STUDIES ON HYPERPLASTIC NODULES IN THE LIVER OF RATS TREATED WITH CARCINOGENIC CHEMICALS

Abstract

Sequential quantitative analyses were made of hyperplastic liver nodules induced by treating male Fischer rats first with diethylnitrosamine (DEN) and then with N-(2-fluorenyl)acetamide (2-FAA), .alpha.-isomer of 1,2,3,4,5,6-hexachlorocyclohexane (.alpha.-BHC), or phenobarbital. The test rats were injected i.p. with 200 mg/kg body wt of DEN, given basal diet containing 2-FAA, .alpha.-BHC or phenobarbital from wk 2-12 and subjected to partial hepatectomy at the end of wk 3. From wk 6, significantly higher percentage areas of hyperplastic nodules/unit area of liver were found in all experimental groups than in the control group. From wk 8, significantly more hyperplastic nodules were found in all experimental groups than in the control group. Continuous administration of .alpha.-BHC or phenobarbital for 12 wk with partial hepatectomy did not induce hyperplastic nodules. Continuous administration of 2-FAA did induce hyperplastic nodules but the percentage areas and number of these nodules were significantly lower than in rats injected with DEN and then given 2-FAA orally, with partial hepatectomy.