Selenocystine is not a cystine antimetabolite in L1210 cells

Selenocystine inhibited the growth in culture of murine L1210 leukemia cells to a greater extent when the cells were supplemented with a high concentration of cystine for optimal growth. Cells which grew suboptimally in a limiting cystine concentration were inhibited to a lesser extent. In this case, the time of onset of selenocystine inhibition coincided with the time of termination of growth at the lower cystine concentration. These observations are contrary to expectation for action of an antimetabolite, and it is concluded that selenocystine cannot be considered a cystine antagonist.