| 14769548 |
Vickery RG, Amagasu SM, Chang R, Mai N, Kaufman E, Martin J, Hembrador J, O'Keefe MD, Gee C, Marquess D, Smith JA: Comparison of the pharmacological properties of rat Na (V) 1.8 with rat Na (V) 1.2a and human Na (V) 1.5 voltage-gated sodium channel subtypes using a membrane potential sensitive dye and FLIPR. Receptors Channels. 2004;10(1):11-23.
A novel, membrane potential sensitive dye and a fluorescence imaging plate reader (FLIPR) have been used to characterize the pharmacological properties of rat Na (v) 1.8 voltage-gated sodium channels (VGSC) in parallel with rat Na (v) 1.2a and human Na (v) 1.5 VGSC subtypes, respectively. The sensitivity of recombinant Na (v) 1.2a-CHO, Na (v) 1.5-293-EBNA, and Na (v) 1.8-F-11 cells to VGSC activators was subtype dependent. Veratridine evoked depolarization of Na (v) 1.2a-CHO and Na (v) 1.5-293-EBNA cells with pEC (50) values of 4.78 +/- 0.13 and 4.84 +/- 0.12, respectively (n = 3), but had negligible effect on Na (v) 1.8-F-11 cells (pEC (50) < 4.5). Type I pyrethroids were without significant effect at all subtypes. In contrast, the type II pyrethroids deltamethrin and fenvalerate evoked direct depolarization of Na (v) 1.8-F-11 and Na (v) 1.5-293-EBNA cells. Deltamethrin potentiated the veratridine-evoked response in Na (v) 1.8-F-11 cells by > or =20-fold, in contrast to a inhibited VGSC activator-evoked depolarization of Na (v) 1.8-F-11 cells with a biphasic concentration-response curve. The calculated pIC (50) values were 8.05 +/- 0.25 (n = 4) and 4.32 +/- 0.21 (n = 4), corresponding to TTX inhibition of endogenous TTX-sensitive (TTX-S), and recombinant Na (v) 1.8 TTX-resistant (TTX-R) VGSCs, respectively. With the exception of TTX, the potencies of a number of ion channel blockers for the Na (v) 1.8, Na (v) 1.2a, and Na (v) 1.5 VGSC subtypes were similar. In summary, these high-throughput FLIPR assays represent a valuable tool for the determination of the relative potencies of compounds at different VGSC subtypes and may prove useful for the identification of novel subtype-selective inhibitors. |
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