Binding characteristics of ligands at the PTH-1 receptor for inhibition of [125I][Nle8,18,Tyr34]bPTH(3–34) binding (3.0-h incubation)
| Ligand | [GTPγS] | No. of Binding States | −log(IC50) at Binding States | % Inhibition at Binding States | F Test p Values for 1 versus 2 State Fit |
|---|---|---|---|---|---|
| μM | |||||
| hPTH(1–34) | 0 | 2 | 8.97 ± 0.17 | 40 ± 5 | <.001, .011 |
| 7.87 ± 0.10 | 60 ± 5 | ||||
| hPTH(1–34) | 10 | 1 | 8.35 ± 0.02 | 100 | .86, .11 |
| [Tyr36]PTHrP(1–36) | 0 | 2 | 8.86 ± 0.55 | 35 ± 14 | <.001, .0085, .0087 |
| 7.22 ± 0.33 | 65 ± 14 | ||||
| [Tyr36]PTHrP(1–36) | 10 | 2 | 8.36 ± 0.05 | 31 ± 4 | <.001, .061, <.001 |
| 7.17 ± 0.09 | 69 ± 4 | ||||
| [Nle8,18,Tyr34]bPTH(1–34) | 0 | 2 | 9.13 ± 0.15 | 78 ± 1 | .028, .021 |
| 7.77 ± 0.01 | 22 ± 1 | ||||
| [Nle8,18,Tyr34]bPTH(1–34) | 10 | 1 | 8.81 ± 0.11 | 100 | 1.0, .13 |
Unlabeled ligands were competed against the binding of the radiolabeled antagonist for 3.0 h at 21°C. See legend to Table 2 for method of data analysis. Data are presented as the mean ± S.E.M. of three experiments or mean ± range for two experiments.