Table 1.
Effect of l-amino acids on the potency of Ca2+ ions as agonists of the Ca2+ receptor
| Amino acid (10 mM) | EC50 for Ca2+ (n) | Δ EC50 for Ca2+ (n) |
|---|---|---|
| l-His | 2.4 ± 0.1 (4) | 1.9 ± 0.2 (4) |
| l-Phe | 2.5 ± 0.1 (7) | 1.8 ± 0.2 (7) |
| l-Tyr | 2.5 ± 0.2 (3) | 1.8 ± 0.2 (3) |
| l-Trp | 2.6 ± 0.3 (3) | 1.6 ± 0.2 (3) |
| l-Cys | 2.8 ± 0.1 (5) | 1.6 ± 0.1 (5) |
| l-Ala | 2.9 ± 0.3 (3) | 1.4 ± 0.04 (3) |
| l-Thr | 3.0 ± 0.1 (3) | 1.1 ± 0.3 (3) |
| l-Asn | 3.1 ± 0.2 (3) | 1.1 ± 0.2 (3) |
| l-Gln | 3.2 ± 0.2 (3) | 1.0 ± 0.2 (3) |
| l-Ser | 3.3 ± 0.2 (3) | 1.0 ± 0.2 (3) |
| l-Glu | 3.5 ± 0.2 (3) | 0.9 ± 0.1 (3) |
| Gly | 3.6 ± 0.5 (3) | 0.7 ± 0.2 (3) |
| l-Pro | 3.6 ± 0.3 (3) | 0.6 ± 0.2 (3) |
| l-Val | 3.6 ± 0.3 (3) | 0.6 ± 0.2 (3) |
| l-Met | 3.6 ± 0.3 (3) | 0.6 ± 0.1 (3) |
| l-Asp | 3.7 ± 0.2 (3) | 0.6 ± 0.3 (3) |
| l-Lys | 3.7 ± 0.1 (3) | 0.6 ± 0.2 (3) |
| l-Arg | 3.7 ± 0.1 (3) | 0.5 ± 0.3 (3) |
| l-Ile | 3.9 ± 0.5 (3) | 0.3 ± 0.1 (3) |
| l-Leu | 4.2 ± 0.3 (3) | 0 ± 0.2 (3) |
| Control | 4.2 ± 0.1 (10) | 0 ± 0 |
Data are shown ± SEM. All experiments were performed at pH 7.4. Δ EC50 is defined as control minus experimental. Unpaired t tests performed on the data set (individual amino acids vs. control) yielded the following results: l-His, l-Phe, l-Trp, l-Tyr, l-Cys, and l-Thr, P = 0.0001; l-Ala, P = 0.0002; l-Asn, l-Gln, l-Ser, and l-Glu, P ≤ 0.01; Gly, l-Pro, l-Val, l-Met, l-Asp, and l-Arg, P < 0.05; l-Lys, P = 0.05; l-Ile, P = 0.31; and l-Leu, P = 0.95.