TABLE 1.
Affinities of different ligands for human, rat and mouse BRS-3, GRP, and NMB receptors in various cells.
| IC50 (nM) | |||||||
|---|---|---|---|---|---|---|---|
| Human | Rat | Mouse | |||||
| BRS-3 | GRPR | NMBR | GRPR | NMBR | GRPR | NMBR | |
| Peptides | hBRS-3/BALB | hGRPR/BALB | hNMBR/BALB | rGRPR/AR42J | rNMBR/BALB | mGRPR/BALB | mNMBR/BALB |
| Peptide #1 | 2.89 ± 0.70 | 0.71 ± 0.03 | 0.21 ± 0.01 | 0.03 ± 0.00 | 0.53 ± 0.08 | 0.42 ± 0.04 | 5.76 ± 1.02 |
| MK-5046 | 102 ± 2 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 |
| 3 F | 909 ± 2 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 |
| 9 D | 121 ± 1 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 |
| 9 F | 495 ± 1 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 |
| 9 G | 70 ± 1 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 | >3,000 |
| GRP | >3,000 | 0.48 ± 0.05 | 65 ± 17 | 0.41 ± 0.00 | 440 ± 70 | 2.70 ± 0.20 | 206 ± 13 |
| NMB | >3,000 | 31.5 ± 2.4 | 0.60 ± 0.02 | 80 ± 5 | 1.21 ± 0.15 | 170 ± 5 | 0.60 ± 0.02 |
The indicated cell type was incubated with 50 pM 125I-[D-Tyr6, β-Ala11, Phe13, Nle14]Bn-(6–14) for 60 minutes at 21°C and binding was determined as described in Materials and Methods. The IC50 was the concentration causing half-maximal inhibition of the saturable binding, calculated using a nonlinear regression curve-fitting program (Prism). In each experiment each value was determined in duplicate, and values given are means and S.E.M. from at least three separate experiments. Abbreviations: BALB 3T3, mouse fibroblast cells; BRS-3, bombesin receptor subtype 3; GRPR, gastrin-related peptide receptor; NMBR, neuromedin B receptor; h, human; r, rat; m, mouse; 3F, 9D, 9F, 9G, nonpeptide chiral diazepine analogs; peptide #1, [D-Tyr6, β-Ala11, Phe13, Nle14]Bn-(6–14); MK-5046, (2S)-1,1,1-trifluoro-2-[4-(1H-pyrazol-1-yl)phenyl]-3-(4-[[1- (trifluoromethyl)cyclopropyl]methyl]-1H-imidazol-2-yl)propan-2-ol; IC50, half- maximal inhibitory concentration; h,r,mBRS-3 stably transfected into BALB cells; h,mGRPR stably transfected into BALB cells; h,r,mNMBR stably transfected into BALB cells and AR42J cells containing native rGRPR. Binding studies could not be performed with rat or mouse BRS-3 because no radioligand is available. Data are calculated from dose-inhibition curves shown in Fig. 1–3.