Table 2.

Effect of _L-amino acids on uptake of [¹⁴C]_L-citrulline in TR-BBB cells

Substrate	Concentration (mM)	Uptake of [14C]L-citrulline (% of control)
Control		100 ± 1.3
L-Citrulline	2	36.0 ± 2.1***
L-Valine	2	31.5 ± 1.4***
L-Leucine	2	49.4 ± 5.8***
	20	17.2 ± 3.9***
L-Phenylalanine	2	13.7 ± 1.8***
	20	13.4 ± 1.4***
L-Glutamine	2	37.5 ± 1.3***
L-Alanine	2	73.0 ± 6.4**
L-Serine	2	79.7 ± 2.5*
L-Cysteine	2	48.4 ± 2.6***
L-Arginine	2	59.9 ± 6.6**
	20	53.2 ± 4.4***
L-Lysine	2	74.5 ± 9.0*
	20	66.78 ± 2.1*
L-Glutamate	2	102.8 ± 7.8
L-Aspatate	2	101.5 ± 8.6

[¹⁴C]_L-Citrulline uptake by TR-BBB cells was performed at pH7.4 and 37 °C for 5 min in the presence or absence of 2–20 mM _L- amino acids. Each value represents the mean ± S.E.M. (n = 3–4). *p < 0.05, **p < 0.01, ***p < 0.001; significantly different from control