Table 3.
Influence of inhibitors on amino acid transport and cation conductance
| Inhibitor | Na+-independent [14C]Ile uptake(% of control) | Icat(% of control) |
|---|---|---|
| None | 100 | 100 |
| Amiloride (10 μM) | 102 ± 8 | 99 ± 2 |
| TEA (1 mM) | 118 ± 17 | 100 ± 2 |
| BaCl2 (1 mM) | 101 ± 7 | 105 ± 4 |
| LaCl3 (300 μM) | 109 ± 5 | 52 ± 4 |
| GdCl3 (300 μM) | 43 ± 10 | 44 ± 4 |
| Niflumate (100 μM) | 87 ± 13 | 100 ± 1 |
| Flufenamate (100 μM) | 79 ± 12 | 96 ± 2 |
| NPPB (100 μM) | 104 ± 14 | 89 ± 3 |
| Hoe 293B (10 μM) | 102 ± 18 | 100 ± 1 |
| Quinidine (500 μM) | 58 ± 20 | 65 ± 11 |
| PMA (50 nM) | 61 ± 11 | n.d. |
| Staurosporine (0.001 mM) | 95 ± 4 | n.d. |
| DTE (5 mM) | 92 ± 8 | 21 ± 6 |
| Mercaptoethanol (1 mM) | 88 ± 14 | n.d. |
Oocytes were injected with 5 ng of both 4F2hc and LAT1 cRNAs, followed by an expression period of 1–2 days. Due to the fast expression of 4F2hc/LAT1 control values ranged from 17 to 70 pmol (2.5 min)−1 depending on the expression period. Na+independent isoleucine uptake was measured with [14C]isoleucine. Icat was determined as the difference between the current in the absence and presence of Na+. Oocytes were incubated with the indicated inhibitors for 5 min prior to and during the transport experiment. A preincubation period of 1 h was used in experiments with phorbolester (PMA) and staurosporine and 30 min in the case of DTE and mercaptoethanol. Transport activity was determined using seven oocytes in two different experiments. n.d., not determined.