Chronic exposure to agmatine results in the selection of agmatine-resistant hepatoma cells.

During our study of the cytostatic effect of agmatine, we were able to isolate an agmatine resistant clone from a parental hepatoma cell line, HTC. These cells, called Agres, had slower growth rate than the parental cells when cultured in normal medium. The modification in polyamine content induced by agmatine was much lower in these cells and ornithine decarboxylase, S-adenosylmethionine decarboxylase and spermidine/spermine acetyltransferase activities were much less affected. By investigating the mechanism responsible for these modifications, it was shown that agmatine and polyamines were not taken up by Agres cells. Their resistance to the antiproliferative effects of agmatine may thus arise from a lack of the polyamine transport system. Moreover, Agres cells were able to take up both glutamic acid and arginine at a rate significantly higher than that detected for HTC cells, most likely to provide components for compensatory increase of PA synthesis. These results emphasize the importance of polyamine transport for cell growth.