The regulation of serine dehydratase and glucose-6-phosphatase in hyperplastic nodules of rat liver during diethylnitrosamine and N-2-fluorenylacetamide feeding.
Changes in the levels of serine dehydratase and glucose-6-phosphatase induced by dietary stimuli or starvation in hyperplastic nodules of rat liver during diethylnitrosamine or N-2-fluorenylacetamide feeding were studied by immuno- and enzyme histochemical methods. The study was performed during carcinogenesis through a combined method of enzyme histochemistry and radioautography. Serine dehydratase was observed diffusely in the cytoplasm of the original hepatocytes in the periportal zone and was induced markedly during diethynitrosamine feeding but only slightly during N-2-fluorenylacetamide feeding. The enzyme was deficient and not inducible in hyperplastic nodules during their developing phase. Later during the feeding period, however, there was an elevation of the level of serine dehydratase and its inducibility with time in the majority of the nodules. A good correlation was observed between serine dehydratase and glucose-6-phosphatase in their elevated levels and response to enviornmental stimuli. There was a minor group of hyperplastic nodules in which the deficiencies of these enzymes persisted and enzyme induction was not observed. A greater number of hyperplastic nodules with persistent enzyme deficiency was seen during diethylnitrosamine carcinogenesis. These results provide further information about the changing biological nature of hyperplastic nodules with respect to their metabolic adaptability and enzyme levels during hepatocarcinogenesis.