Precancerous Loss of 5-Hydroxytryptophan Decarboxylase Activity

The purpose of this experimental work was to determine whether the precancerous loss of rat liver 5-hydroxytryptophan (5-HT) decarboxylase was associated with sequential atrophic alterations preceding hepatocarcinogenesis. To test whether such an association existed, three experimental conditions were employed in which hepato carcinogenesis was either markedly delayed or prevented. Under all three experimental conditions the losses of 5-HT decarboxylase activity approximated those observed in precancerous livers of rats fed 3'-methyl-4-dimethylaminoazobenzene. It was also shown that the losses were not associated with proliferation stimulated by partial hepatectomy. It was concluded that the precancerous loss of 5-HT decarboxylase activity either (a) was associated with factors other than those involved with sequen tial atrophic alterations preceding hepatocarcinogenesis or (b) if associated with the atrophic alterations, was a necessary but insufficient reaction leading to malignant transformation. The possible correlation between the activity losses and protein-bound azo dyes was discussed.