2-Aminoethoxydiphenyl borate blocks electrical coupling and inhibits voltage-gated K⁺ channels in guinea pig arteriole cells

Abstract

2-Aminoethoxydiphenyl borate (2-APB) analogs are potentially better vascular gap junction blockers than others widely used, but they remain to be characterized. Using whole cell and intracellular recording techniques, we studied the actions of 2-APB and its potent analog diphenylborinic anhydride (DPBA) on vascular smooth muscle cells (VSMCs) and endothelial cells in situ of or dissociated from arteriolar segments of the cochlear spiral modiolar artery, brain artery, and mesenteric artery. We found that both 2-APB and DPBA reversibly suppressed the input conductance (G(input)) of in situ VSMCs (IC(50) ≈ 4-8 μM). Complete electrical isolation of the recorded VSMC was achieved at 100 μM. A similar gap junction blockade was observed in endothelial cell tubules of the spiral modiolar artery. Similar to the action of 18β-glycyrrhetinic acid (18β-GA), 2-APB and DPBA depolarized VSMCs. In dissociated VSMCs, 2-APB and DPBA inhibited the delayed rectifier K(+) current (I(K)) with an IC(50) of ∼120 μM in the three vessels but with no significant effect on G(input) or the current-voltage relation between -140 and -40 mV. 2-APB inhibition of I(K) was more pronounced at potentials of ≤20 mV than at +40 mV and more marked on the fast component than on the slow component, which was mimicked by 4-aminopyridine but not by tetraethylammonium, nitrendipine, or charybdotoxin. In contrast, 18β-GA caused a linear inhibition of I(K) between 0 to +40 mV, which was similar to the action of tetraethylammonium or charybdotoxin. Finally, the 2-APB-induced inhibition of electrical coupling and I(K) was not affected by the inositol 1,4,5-trisphosphate receptor antagonist xestospongin C. We conclude that 2-APB analogs are a class of potent and reversible vascular gap junction blockers with a weak side effect of voltage-gated K(+) channel inhibition. They could be gap junction blockers superior to 18β-GA only when Ca(2+)-actived K(+) channel inhibition by the latter is a concern but inositol 1,4,5-trisphosphate receptor and voltage-gated K(+) channel inhibitions are not.

Bumetanide Hyperpolarizes Madin–Darby Canine Kidney Cells and Enhances Cellular Gentamicin Uptake by Elevating Cytosolic Ca2+ Thus Facilitating Intermediate Conductance Ca2+-Activated Potassium Channels

“…The method of conventional whole-cell recording was similar to that published previously [30, 31]. Briefly, the glass micropipette of ~1 m tip (4 – 7 MΩ) was filled with a normal internal solution (NIS) containing (in mM): K-gluconate 130, NaCl 10, CaCl 2 2.0, MgCl 2 1.2, HEPES 10, EGTA 5 (free Ca 2+ =118 nM) and glucose 7.5 (pH7.2 and 290 mOsm l −1 ).…”

Potent analgesic effects of a store-operated calcium channel inhibitor

“…Unfortunately, most of the commercially available SOC channel inhibitors, such as lanthanum, SKF 96365, and 2-aminoethyldiphenylborate, are nonspecific or have complex effects on SOC entry [24; 37; 38; 47; 60; 70]. Two groups identified YM-58483, a pyrazole derivative, as a potent inhibitor of store-operated Ca2+ entry [29; 71].…”

2-Aminoethyl diphenyl borinate (2-APB) inhibits TRPM7 channels through an intracellular acidification mechanism

“…[3][4][5][6][7][8] During the last decade, effects of 2-APB on numerous other ion transport proteins have been described. For example, 2-APB is an inhibitor of sarcoplasmic-endoplasmic reticulum Ca 2+ -ATPase (SERCA) pumps, 9 gap junction connexins, 10 potassium channels 11 and volume-regulated anion channels 12 at micromolar concentrations. Members of the Transient Receptor Potential (TRP) family of cation channels were also shown to be sensitive to this compound.…”

“…37 Thus, inhibition of store-operated Ca 2+ entry by 2-APB in these cells may also be accompanied by inhibition of Kv1.3 and this would result in a diminished driving force for Ca 2+ entry into the cell. In such cases 2-APB would reduce the cytoplasmic Ca 2+ levels more drastically than would be expected if it only affected Orai channels 11 ). In studies where 2-APB blockade of TRP channels has been investigated in detail, it has been reported to involve direct interaction with the channel protein.…”