The effects of 2-chloroethylisocyanate, ethylisocyanate and sodium cyanate on the uptake of isotope-labeled thymidine, leucine and H2O were compared in rat liver and hepatomas. The data suggested that carbamoylating agents may have a common property of inhibiting uptake of compounds in hepatomas under conditions in which there is a smaller effect or no action in the liver of tumor-bearing rats. The distinction between tissues may have been mediated, in part, through effects on tumor circulation and was less apparent when isolated cells were studied in vitro. Preferential inhibitory effects of carbamoylating agents on the uptake of leucine and H2O were also observed with a murine hepatoma, but they were not as great as with rat hepatomas.
