Table 1.

RDR increases uptake of neutral amino acids

[3H]amino acid	Radioactivity uptake by NIH 3T3 cells containing		RDR-specific change, %
	LXSN	L(RDR)SN
Alanine	5,200  ±  600	6,400  ±  200	23
Serine	46,800  ±  2,100	49,300  ±  4,600	5.3
Glutamine	22,400  ±  700	25,000  ±  1,300	12
Glutamate	6,400  ±  500	5,900  ±  300	−7.0

Amino acid transport in NIH 3T3 cells expressing either the empty vector pLXSN or the receptor-containing vector pL(RDR)SN was examined. Uptake of 20 nM [³H]amino acid was measured for 2 min at 25°C in medium containing sodium. The data are presented as mean uptake (cpm/well per min) ±SD of triplicate measurements. Alanine uptake was measured in four independent experiments (mean increase of 29 ± 15%), whereas uptake measurements for the other amino acids were performed once.