Table I. Effect of amino acids on [³⁵S]l-cystine accumulation.

Amino acid (10 mM)	% uninhibited± SEM	Greene et al. (1990)
l-methionine	73 ± 12 (n = 4)	51 ± 4
l-leucine	75 ± 12 (n = 4)	61 ± 4
l-alanine	69 ± 9 (n = 6)	86
l-valine	60 ± 7 (n = 6)	66
l-phenylalanine	87 ± 7 (n = 6)	78
l-proline	102 ± 9 (n = 6)	87
l-serine	81 ± 4 (n = 4)	79
l-threonine	69 ± 7 (n = 6)	104
l-cysteine	25 ± 4 (n = 7)	n.d.
l-glutamic acid	102 ± 11 (n = 4)	n.d.

Values are expressed as the mean ± SEM of n independent observations, and are compared with those obtained by Greene et al. (1990) for the lysosomal cystine countertransport activity of mouse L-929 fibroblasts.

n.d., not determined.