Cj. Hatton et C. Peers, EFFECTS OF CYTOCHROME-P-450 INHIBITORS ON IONIC CURRENTS IN ISOLATED RAT TYPE-I CAROTID-BODY CELLS, American journal of physiology. Cell physiology, 40(1), 1996, pp. 85-92
Hypoxic chemoreception in the carotid body involves selective inhibiti
on of K+ channels in type I cells. We have investigated whether cytoch
rome P-450 may act as an O-2 sensor coupling hypoxia to K+ channel inh
ibition, by investigating the actions of P-450 inhibitors to modulate
channel activity (recorded using patch-clamp techniques) in type I cel
ls isolated from 8- to 12-day-old rat pups. The imidazole antimycotic
P-450 inhibitors miconazole and clotrimazole (1-10 mu M) inhibited the
Ca2+-activated (K-Ca) and voltage-gated K+ (K-v) currents in isolated
type I cells. Single-channel recordings indicated that the K-Ca chann
els could be inhibited directly by miconazole. Miconazole also irrever
sibly inhibited Ca2+ channel currents. By contrast, acute application
of the suicide substrate P-450 inhibitor, 1-aminobenzotriazole (1-ABT;
3 mM) was without effect on K+ or Ca2+ currents. Hypoxia (16-23 mmHg)
reversibly inhibited K+ currents and prevented the inhibitory actions
of miconazole. Furthermore, the inhibitory actions of miconazole coul
d be partially reversed by hypoxia. Pretreatment of cells for 60 min w
ith 3 mM 1-ABT substantially reduced the inhibitory actions of hypoxia
on K+ currents. Our results indicate that imidazole antimycotic P-450
inhibitors can directly and nonselectively inhibit ionic channels in
type I cells but, more importantly, provide evidence to suggest that h
ypoxic inhibition of K+ currents in type I cells is mediated in part a
t least by cytochrome P-450.