The isolation of a canavanine-resistant mouse embryonal carcinoma cell line which has reduced arginine transport

A mouse embryonal carcinoma cell line resistant to the toxic arginine analogue -canavanine has been isolated. Kinetic studies of the transport of arginine in the canavanine-sensitive parental cell indicate that there are two arginine uptake systems which operate at different substrate concentrations. The canavanine-resistant variant shows a reduction in the rate at which it can transport arginine at all substrate concentrations. This is not, however, due to the complete loss of either uptake system. The observation that the rate of arginine transport at high substrate concentrations is reduced in the variant can be explained, at least in part, by an increase in chromosome number and cell volume. This is not true of the reduction in the low substrate concentration uptake system. The observation that the reductions in the two uptake systems can be dissociated in this way provides support for the conclusion, based on the kinetic data from the parental cell, that there are two independent arginine transport systems in this mouse embryonal carcinoma cell line.