Figure 6. 5,6-EET-potentiation of K_Ca3.1 currents.

A) Whole-cell current traces; from left to right: potentiation of Ca²⁺-pre-activated hK_Ca3.1 by 5,6-EET (1 µM) followed by inhibition of the current by AA (10 µM), insensitivity of the hK_Ca3.1^T250S/V275A mutant to 5,6-EET, and insensitivity of the hK_Ca3.1^T250S/V275A mutant to AA (10 µM) and TRAM-34 (1 µM). The hK_Ca3.1 currents were pre-activated by 250 nM Ca²⁺. Panel on the right: summary data. B) From left to right: Ca²⁺-pre-activation of rat endothelial rK_Ca3.1 by 3 µM Ca²⁺ and current inhibition by 14,15-EET (1 µM), larger currents in the presence of 5,6-EET (1 µM) and inhibition by AA (10 µM). Panel on right: Summary data: dependence of 5,6-EET-potentiation on the intracellular Ca²⁺. Note that at a low intracellular Ca²⁺ (0.1 µM) that is below/near the threshold for K_Ca3.1 activation, 5,6-EET did not potentiate the current. In contrast, potentiation occurred at an intracellular Ca²⁺ concentration that is near the EC₅₀ for Ca²⁺-activation of K_Ca3.1 as well as at a saturating Ca²⁺ concentration. C) DHA (1 µM) blocked Ca²⁺-pre-activated mK_Ca3.1 in murine fibroblasts. D) Pentacyclic triterpenes did not modulate murine fibroblast mK_Ca3.1 at a concentration of 1 µM. Data are means ± SEM (% inhibition of K_Ca3.1-current normalized to initial peak amplitude after establishing electrical access (by seal rupture) and stable Ca²⁺-activation of K_Ca3.1-outward currents); Numbers in the graphs indicate the number of whole-cell experiments; *P<0.05 vs. control (peak amplitude of the K_Ca3.1-current in the respective cell); One-way ANOVA and Tukey post hoc test.