Table 1.
Uptake of aspartate, glutamate, or sialic acid by the sialin-containing proteoliposomes in the presence of various compounds
| Compound | Concentration, μM | Uptake, % of control |
||
|---|---|---|---|---|
| l-Aspartate | l-Glutamate | Sialic acid | ||
| Control | 100.0 ± 9.2 | 100.0 ± 9.3 | 100.0 ± 8.4 | |
| Valinomycin | 2 | 23.9 ± 5.5** | 16.5 ± 8.9** | 101.0 ± 8.7 |
| Nigericin | 2 | 77.8 ± 7.7* | 80.2 ± 16.8 | 17.3 ± 9.4** |
| Val + Nig | 2 | 0.0 ± 8.9** | 0.0 ± 9.0** | 13.0 ± 5.6** |
| CCCP | 1 | 6.2 ± 7.7** | 24.8 ± 4.1** | 15.6 ± 5.1** |
| Evans blue | 1 | 20.7 ± 3.7** | 14.6 ± 6.9** | 114.4 ± 3.3 |
| l-aspartate | 5,000 | 0.0 ±1.7** | 8.7 ± 10.0** | 109.9 ± 1.1 |
| d-Aspartate | 5,000 | 3.2 ± 3.3** | 6.9 ± 6.2** | 92.1 ± 6.6 |
| tHA | 5,000 | 0.0 ± 7.3** | 0.0 ± 0.8** | 84.2 ± 11.6 |
| l-glutamate | 5,000 | 1.3 ± 2.0** | 0.0 ± 4.5** | 98.0 ± 12.0 |
| Sialic acid | 5,000 | 57.5 ± 11.0* | 51.2 ± 10.8* | 9.8 ± 8.7** |
| l-lactate | 5,000 | 95.9 ± 10.9 | 97.0 ± 2.7 | 11.5 ± 8.0** |
| Succinate | 5,000 | 93.0 ± 3.0 | 84.7 ± 9.9 | 20.7 ± 8.4** |
Sialin-mediated Δψ-dependent uptake of aspartate and glutamate and ΔpH-dependent uptake of sialic acid were measured, and the effects of various compounds were examined as described in the legend of Fig. 4. Control activities (100%) correspond to 2.9 nmol/min per mg of protein for aspartate uptake, 2.3 nmol/min per mg of protein for glutamate uptake, and 67 nmol/min per mg of protein for sialic acid uptake. Val, valinomycin; Nig, nigericin.
*, P < 0.05;
**, P < 0.001.