RNA labelling with 3H-orotic acid and 3H-fluorouracil of rat liver tumour following transient hepatic arterial ischaemia.

Recent studies have demonstrated that transient (1 h) hepatic arterial ischaemia is followed by increased incorporation of labelled thymidine into tumour DNA 24 h later. The present study aimed at investigating if and when there is a corresponding increase in incorporation of labelled 5-fluorouracil (5-FU) or orotic acid into tumour tissue. Incorporation was studied at 0, 6, 24 and 48 h after discontinuation of transient hepatic arterial ischaemia in Wistar-Furth rats having liver tumour. The transient ischaemia was followed by increased RNA and RNA/DNA ratios in normal liver but not in tumour. Incorporation of orotic acid into RNA and DNA was unchanged in tumour but increased at 0 and 6 h in normal liver. Incorporation of 5-FU decreased with time in liver and tumour DNA and in tumour RNA. It is suggested that 5-FU has an optimal effect on tumour tissue when infused immediately after transient hepatic arterial ischaemia.