Table 3.
Selective inhibition of IP3 receptor subtypes by common antagonists
| IP3R1 | IP3R2 | IP3R3 | ||||
|---|---|---|---|---|---|---|
| ΔpEC50 (M) | ΔMax (%) | ΔpEC50 (M) | ΔMax (%) | ΔpEC50 (M) | ΔMax (%) | |
| Heparin, 400 μg·mL−1 | 1.88 ± 0.05* | −7 ± 2 | ND | – | 2.34 ± 0.07* | −3 ± 3 |
| Heparin, 800 μg·mL−1 | ND | – | 1.49 ± 0.09* | −4 ± 2 | ND | – |
| Caffeine, 70 mM | 0.61 ± 0.07* | 12 ± 4 | −0.2 ± 0.07 | −1 ± 0 | −0.07 ± 0.08 | 0 ± 5 |
| 2-APB, 50 μM | 0.84 ± 0.12* | 0 ± 4 | −0.05 ± 0.10 | 0 ± 4 | 0.02 ± 0.09 | 8 ± 4 |
| Xestospongin C, 20 μM | 0.21 ± 0.10* | 6 ± 2* | −0.06 ± 0.04 | 1 ± 1 | 0.12 ± 0.03* | 1 ± 2 |
| Xestospongin D, 20 μM | 0.26 ± 0.09* | 18 ± 2* | −0.15 ± 0.05 | 8 ± 3* | 0.21 ± 0.10* | 2 ± 2 |
Summary of the functional analyses of antagonists on IP3-evoked Ca2+ release from permeabilized DT40-IP3R1-3 cells. The pEC50 values for IP3 and the maximal Ca2+ release are each expressed relative to the response evoked in paired controls without antagonist (Δ = control – response with antagonist). A positive Δ value demonstrates an inhibition of IP3-evoked Ca2+ release by the antagonist. The results with Xestospongins C and D are pooled from experiments that included pre-incubation periods of 7 and 12 min (see Supporting Information Table S1). Results are means ± SEM from three to nine experiments.
Denotes a value significantly greater than 0 (P < 0.025, one-tailed test).
ND, not determined.