Antagonistic properties (K b) of the peptides
| Peptide | Kb | ||
|---|---|---|---|
| VPAC1R | VPAC2R | PAC1 | |
| nM | |||
| [Tyr9,Dip18]VIP(6–23) | 79 ± 7 (0.5%) | >500 (0.0%) | >500 (0.1%) |
| [Tyr9,Dip18]VIP(6–28) | 16 ± 1 (0.3%) | 94 ± 9 (0.0%) | >500 (0.2%) |
| [Tyr9,Arg16,Dip18]VIP(6–23) | 60 ± 5 (0.3%) | N.D. | N.D. |
| [Tyr9,Dip18,Leu22]VIP(6–23) | >500 (0.4%) | N.D. | N.D. |
| [Tyr9,Dip18]VIP(6–28)/PACAP(29–38) | 130 ± 60 (0.3%) | 61 ± 8 | 100 ± 50 |
| [Lys1,Pro2,Arg3,Arg4,Pro5,Tyr9,Dip18]VIP(6–28) | 30 ± 10 (1.7%) | N.D. | N.D. |
Peptides unable to stimulate cAMP at 10−6 M peptide (i.e., peptides having less than 2% response compared with 10−6 M VIP) were tested for their ability to inhibit the VIP-induced cAMP response. A dose-response curve for VIP with 300 nM peptide was used to evaluate K b (see under Materials and Methods). The results given are the mean and S.E.M. values of three to six determinations. The ability of the peptides to stimulate cAMP at 10−6 M is shown in brackets as percentage of the cAMP production of 1 μM VIP.
N.D., not determined.