Mechanism of growth stimulation of L1210 cells by 2-mercaptoethanol in vitro. Role of the mixed disulfide of 2-mercaptoethanol and cysteine.

The mechanism of the growth-promoting action of 2-mercaptoethanol on mouse lymphoma L1210 cells in vitro has been studied. The normal line of L1210 is deficient in its capacity to take up cystine, and this limits the growth of the cells in normal culture media containing cystine. In the presence of 2-mercaptoethanol, the cells obtain a high capacity to utilize cystine in the medium. The reaction of 2-mercaptoethanol with cystine produces a mixed disulfide of 2-mercaptoethanol and cysteine. The mixed disulfide is taken up by the cells mainly via the L system, a transport system for neutral alpha-amino acids such as leucine. The mixed disulfide within the cells is rapidly reduced to produce cystine and 2-mercaptoethanol which escapes rapidly into the medium and reacts with cystine again. With the aid of this cyclic action of 2-mercaptoethanol, the cells are able to utilize cystine constantly.