Table 4.
Comparison of affinities of various natural and synthetic agonists for GRP-receptors and NMB-receptors in human and rat.
| IC50 (nM) |
IC50 (nM) |
||||
|---|---|---|---|---|---|
| Bombesin Analogue | Peptide Name/# |
HuTu-80 (hGRPR) |
AR42J (rGRPR) |
NCI-H1299 (hNMBR) |
C6 (rNMBR) |
| Natural Peptides | |||||
| Bombesin-related | |||||
| Bombesin | Bn | 0.17 ± 0.01 | 0.691 ± 0.08 | 3.7 ± 0.2 | 21 ± 7 |
| Gastrin-releasing peptide (14–27) | GRP | 0.19 ± 0.01 | 0.407 ± 0.08 | 123 ± 16 | 230 ± 16 |
| Alytesin | Aly | 0.12 ± 0.01 | 0.309 ± 0.008 | 1.86 ± 0.07 | 3.16 ± 0.17 |
| Neuromedin C | NMC | 0.14 ± 0.01 | 0.490 ± 0.027 | 75.9 ± 3.9 | 117 ± 8 |
| Neuromedin B-related | |||||
| Neuromedin B | NMB | 35.08 ± 0.88 | 35.7 ± 1.1 | 0.054 ± 0.002 | 0.398 ± 0.02 |
| NMB30 | NMB30 | 15.31 ± 0.26 | 21.18 ± 0.15 | 0.304 ± 0.018 | 0.448 ± 0.009 |
| Rohdei-litorin | Roh-Lit | 190 ± 10 | 23.2 ± 0.75 | 0.26 ± 0.12 | 1.02 ± 0.07 |
| Litorin | Lit | 2.69 ± 0.13 | 1.66 ± 0.083 | 0.56 ± 0.03 | 0.891 ± 0.05 |
| Ranatensin | Ran | 2.24 ± 0.11 | 1.08 ± 0.032 | 4.47 ± 0.16 | 5.63 ± 0.24 |
| P-GL | PG-L | 0.68 ± 0.03 | 0.490 ± 0.027 | 0.89 ± 0.05 | 3.09 ± 0.10 |
| Phyllolitorin-related | |||||
| Phyllolitorin | PLL | > 3,000 | 190 ± 14 | 2.34 ± 0.07 | 20.4 ±1.33 |
| [Leu8]phyllolitorin | LeuPLL | 524 ± 26 | 120 ± 8 | 295 ± 17 | 145 ± 10 |
| Synthetic | |||||
| [Leu14]Bn | #1 | 1.0 ± 0.1 | 24.8 ± 0.9 | 295 ± 11 | 324 ± 20 |
| [Tyr4,Nleu14]Bn | #2 | 0.4 ± 0.1 | 1.36 ± 0.10 | 41.7 ± 1.8 | 74.1 ± 5.9 |
| [D-Trp8,Leu14]Bn | #3 | 417 ± 16 | > 3,000 | > 3,000 | > 3,000 |
| [D-Ala11]Bn | #4 | 0.54 ± 0.04 | 3.55 ± 0.15 | 190 ± 14 | 43.7 ± 1.6 |
| [N-3-Pentanyl,D-Phe6,D-Ala11,Leu14]Bn(6–14) | #5 | 16.6 ± 0.7 | 81.3 ± 3.4 | > 3,000 | 1230 ± 59 |
| [D-Phe6,D-Ala11,Leu14]Bn(6–14) | #6 | 10.0 ± 0.8 | 33.1 ± 1.7 | 1,000 ± 20 | 55 ± 4 |
| [D-Phe6]Bn(6–14) | #7 | 0.17 ± 0.01 | 0.98 ± 0.04 | 2.14 ± 0.06 | 5.9 ± 0.3 |
| [D-Cys6,D-Ala11,Cys14]Bn(6–14) | #8 | 437 ± 22 | 1096 ± 81 | > 3,000 | 589 ± 13 |
| [D-Tyr6,βAla11,Phe13,Nle14]Bn(6–14) | #9 | 0.027 ± 0.002 | 0.020 ± 0.001 | 0.76 ± 0.03 | 0.977 ± 0.059 |
| [D-Phe6, βAla11,Phe13,Nle14]Bn(6–14) | #10 | 0.048 ± 0.005 | 0.033 ± 0.002 | 0.32 ± 0.02 | 1.29 ± 0.053 |
| [D-Tyr6,Asn7,βAla11,Phe13, Nle14]Bn(6–14) | #11 | 1.0 ± 0.1 | 1.20 ± 0.03 | 31.6 ± 1.1 | 324 ± 29 |
| [D-Ser-Ser-D-Ser-D-Tyr6,Asn7, βAla11, Phe13, Nle14]Bn(6–14) | #12 | 6.8 ± 0.2 | 4.19 ± 0.17 | 11.2 ± 0.7 | 31.6 ± 2.0 |
HuTu-80 (1.5×106 cells/ml) and AR42J (1.0×106 cells/ml) were incubated with 50pM 125I-[Tyr4]Bn, hNMBR-NCI-H1299 transfected (1×106 cells/ml) and C6 (1.0×106 cells/ml) with 125I-[D-Tyr0]NMB for 1 h at 22°C. Increasing concentrations of unlabeled peptide were added, and dose-response curves were analyzed using KaleidaGraph. Results are expressed as the peptide concentration causing a half-maximal decrease (IC50) in saturable binding. Values are mean ± S.E. from at least 4 experiments. >3,000 means the affinity was greater than 3,000 nM.
Abbreviations: GRP, gastrin-releasing peptide; Bn, Bombesin; remainder abbreviations see Table 1.