Cytochrome P-450 (P-450) is a NADPH-requiring and O2-dependent monooxygenase system. It is present in lung and has been postulated to act as an O2 sensor in hypoxic pulmonary vasoconstriction. To determine whether P- 450 is involved in the regulation of voltage-gated K+ (K(V)) channel activity in pulmonary artery (PA) myocytes, we used the whole cell patch- clamp technique to evaluate the effects of P-450 inhibitors on K(V) channel currents (I(K(V))) and membrane potential (E(m)). Bath application of the P- 450 inhibitors clotrimazole, miconazole, and 1-aminobenzotriazole (1-ABT) significantly and reversibly inhibited steady-state I(K(V)) (I(K88)) and depolarized PA cells bathed in either Ca2+-containing (1.8 mM) or Ca2+- free [0.5-1 mM ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid present] bath solution. Clotrimazole (1 μM), miconazole (10 μM), and 1-ABT (1 mM) reversibly reduced I(K88), elicited by a test potential of +80 mV, by 40, 70, and 31%, respectively. pretreatment of PA smooth muscle cells with 10 mM 4-aminopyridine (4-AP) prevented the subsequent inhibitory effect of clotrimazole on I(K(V)). However, pretreatment of the cells with 1 mM tetraethylammonium negligibly altered the effects of miconazole on I(K(V)) and E(m). In current-clamp (I = 0) measurements, clotrimazole depolarized PA myocytes by 9 and 11 mV during perfusion with Ca2+-containing and Ca2+- free bath solution, respectively. 1-ABT also caused a 9-mV depolarization in PA myocytes bathed in Ca2+-free solution. These effects are similar to those induced by hypoxia, reduced glutathione, and 4-AP. Clotrimazole also decreased I(K(V)) and depolarized mesenteric arterial myocytes. These data raise the possibility that the P-450 system, due to its influence on I(K(V)) and sensitivity to O2 tension and NADPH, may play a role in linking the regulation of pulmonary vascular tone to the alteration of cellular redox status through a common pathway of K(V) channel activity.
ASJC Scopus subject areas
- Cell Biology