Jt. Hulme et Ch. Orchard, Effect of acidosis on transient outward potassium current in isolated rat ventricular myocytes, AM J P-HEAR, 278(1), 2000, pp. H50-H59
Citations number
31
Categorie Soggetti
Cardiovascular & Hematology Research
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
The effect of acidosis on the transient outward K+ current (I-to) of rat ve
ntricular myocytes has been investigated using the perforated patch-clamp t
echnique. When the holding potential was -80 mV, depolarizing pulses to pot
entials positive to -20 mV activated I-to in subepicardial cells but activa
ted little I-to in subendocardial cells. Exposure to an acid solution (pH 6
.5) had no significant effect on I-to activated from this holding potential
in either subepicardial or subendocardial cells. When the holding potentia
l was -40 mV, acidosis significantly increased It, at potentials positive t
o -20 mV in subepicardial cells but had little effect on I-to in subendocar
dial cells. The increase in I-to in subepicardial cells was inhibited by 10
mM 4-aminopyridine. In subepicardial cells, acidosis caused a +8.57-mV shi
ft in the steady-state inactivation curve. It is concluded that in subepica
rdial rat ventricular myocytes acidosis increases the amplitude of I-to as
a consequence of a depolarizing shift in the voltage dependence of inactiva
tion.