Evidence suggests that Kv channel activity in PAMs may be altered by inhibition of mitochondrial function. Therefore, the effect of ETC inhibitors myxothiazol, antimycin A (AA) and rotenone (all 1 μM), on Kv currents (I_Kv) was investigated using a patch clamp technique at room temperature. Male Wistar rats (225-300 g) were humanely killed. PAMs were isolated from small pulmonary arteries (〈400 μM external diameter) using collagenase (1 mg/ml) and papain (0.5 mg/ml). I_Kv was isolated using 1 μM paxilline and 10 μM glibenclamide to eliminate Ca²⁺ activated and ATP-sensitive K⁺ currents, respectively. The external solution contained (mM): 130 NaCl, 5 KCl, 1.2 MgCl₂, 1.5 CaCl₂, 10 HEPES, 10 glucose and PAMs were dialysed with (mM): 140 KCl, 0.5 MgCl₂, 0.5 CaCl₂, 10 HEPES, 10 EGTA, pH=7.2. Effects on I_Kv were compared in terms of relative shifts in the half-activation, V_a, and half-inactivation, V_h, potentials (ΔV_a and ΔV_h, respectively, obtained in the absence and presence of inhibitors in the same PAM) derived from the Boltzmann fit of the steady-state activation and availability of I_Kv. Holding potential was -80 mV. Data are expressed as mean±s.e.m. and compared using the students paired t-test (p〈0.05 considered significant). Rotenone (a complex I inhibitor) had no effect upon I_Kv activation but significantly shifted the I_Kv availability to more negative voltages (ΔV_h=-5.1±1.9 mV, n=7, p〈0.04). The slope factor (k_h) was also significantly reduced (8.6±1.1 mV vs. 11.8±1.2 mV, control, n=7, p〈0.03). AA and myxothiazol inhibit ETC by blocking proximal and distal to ubisemiquinone in the enzyme Q cycle in complex III, respectively. Whilst myxothiazol had no effect upon ΔV_a or ΔV_h, AA caused a significant leftward shift in both I_Kv activation (ΔV_a=-15.4±3 mV) and inactivation (ΔV_h=-12±3.2 mV, n=7, p〈0.01). Significant increases in the slope of activation and inactivation dependencies were also observed (0.01〈p〈0.04). To study the involvement of cell redox state, the effect of hydrogen peroxide (H₂O₂) and reduced glutathione (GSH) on rotenone and AA was evaluated. Application of 300 μM H₂O₂ caused a leftward shift in I_Kv activation but not inactivation and pre-treatment with H₂O₂ did not significantly block effects of AA. Interestingly with rotenone, a significant rightward shift in I_Kv activation was observed in the presence of H₂O₂ (ΔV_a=6.1±1.9 mV, n=6, p〈0.05). Cell dialysis with 1 mM GSH blocked rotenone-induced shift in I_Kv inactivation (V_h=-0.7±2.8 mV, n=7), however a significant shift in both activation (ΔV_a=-7.1±3 mV, n=15) and inactivation (ΔV_h=-8.7±2.5 mV, n=14) dependencies was seen with AA. Our findings suggest that the effects of AA, but not rotenone, on I_Kv in PAMs appear to be independent of cell redox state.