The purpose of this study was to investigate if the oxygen-sensitive K
channel is present in the carotid body cells of adult cats, and if al
l carotid body cells express the oxygen-sensitive K channel. A standar
d patch-clamp technique with a whole-cell configuration was applied to
cultured carotid body cells from adult cats. The cells were continuou
sly perfused with Krebs equilibrated with 5% CO2/air or 5% CO2/argon a
t room temperature. The results showed that electrophysiologically at
least two types of cells existed in cultured cat carotid body cells. O
ne type expressed the oxygen sensitive K channel and the other express
ed the oxygen-insensitive K channel. The oxygen-sensitive K channel wa
s voltage-dependent with a threshold potential of -30 mV. No inactivat
ion was observed during 30 ms of stimulation. The slope of the steady-
state current-voltage curve was almost linear in the range from -30 mV
to +50 mV. Hypoxia (pO(2) = 25 mmHg) reversibly depressed the K curre
nt by 22%. The current was inhibited by 4-aminopyridine (10 mM) and te
traethylammonium (4-25 mM), but insensitive to charybdotoxin (100 nM).
The oxygen-insensitive K channel showed similar characteristics to th
at of the oxygen-sensitive K channel in the threshold and the speed of
activation, and the shape of I-V curve. The cat is the third species
in which the oxygen-sensitive K channel was found in the carotid body.
The sensitivity of K channels to oxygen may be a unique feature of ch
emosensory cells, but the properties of the oxygen-sensitive K channel
s are different among cats, rats, and rabbits.