Abilities of VIP, [Lys15, Arg16, Leu27]VIP(1–7)GRF(8–27), and Ro 25-1553 to interact with human VPAC1 receptor and VPAC2 receptor cells containing native receptor or stably transfected human VPAC1 or VPAC2
| Peptide | Affinity IC50 (nM) | |||||
|---|---|---|---|---|---|---|
| hVPAC2/ | hVPAC1/ | |||||
| Sup T1 | PANC1 | CHO | T47D | PANC1 | CHO | |
| VIP | 5.3 ± 0.1 | 6.9 ± 0.3 | 2.1 ± 0.1 | 1.6 ± 0.1 | 1.7 ± 0.1 | 0.20 ± 0.01 |
| [Lys15,Arg16,Leu27]VIP(1–7)GRF(8–27) | >3000 | >3000 | >3000 | 8.9 ± 1.3 | 7.7 ± 0.5 | 1.7 ± 0.2 |
| Ro 25-1553 | 3.9 ± 0.2 | 15.9 ± 1.4 | 2.1 ± 0.2 | 1023 ± 162 | 1202 ± 136 | 1269 ± 211 |
Sup T1 human lymphoblastoma cells, hVPAC2/PANC1, and hVPAC2/CHO cells were incubated with 75 pM 125I-labeled peptide and various concentrations of unlabeled VIP and analogs as described in the legend to Fig. 1. T47D breast cancer cells, which natively possess hVPAC1 (Igarashi et al., 2002), hVPAC1/PANC1, and hVPAC1/CHO cells were incubated with 75 pM [125I]VIP and various concentrations of the unlabeled peptides as performed previously (Igarashi et al., 2002). The IC50 was the concentration causing half-maximal inhibition of the saturable binding caused by 1 μM VIP, calculated using the curve-fitting program KaleidaGraph. In each experiment each value was determined in duplicate, and values given are means ± S.E.M. from at least three separate experiments.