Approach to the mechanism of Zajdela's hepatoma cell growth inhibition induced by concanavalin A and phytohaemagglutinin.

Cell growth of tumour ascites cells was inhibited by concanavalin A, phytohaemagglutinin and Ricinus lectin at 2-100 micrograms/ml. As expected, the Ricinus lectin inhibited the protein synthesis estimated by leucine incorporation and decreased thymidine incorporation, whereas concanavalin A and phytohaemagglutinin stimulate the uptake and the incorporation of both leucine and thymidine, and thus, synthesis of protein and DNA. These results suggest that different mechanisms are involved in the hepatoma cell growth inhibition by the lectins. This difference was not related to the kinetic characteristics of the lectin interactions with the cells which represent a first and necessary step. It was showed that concanavalin A and phytohaemagglutinin as well as chloroquine inhibited the 14C-labelled asialofetuin degradation. We can conclude that Ricinus lectin present a toxic effect whereas both concanavalin A and phytohaemagglutinin show an anti-protease activity.