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KMID : 0388419960050020049
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Konkuk Journal of Medical Sciences
1996 Volume.5 No. 2 p.49 ~ p.60
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The Effects of Extracellular pH Change on Tension and Ca2+-activated K+Current in the Rabbit Portal Vein
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Abstract
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We investigated the effects of changes in external pH on tension of smooth muscle and outward currents of single myocytes from the portal vein of the rabbit at room temperature.
When external pH altered tension in high-K+ depolarized small strips of portal vein, in creasing external pH( 7.4→7.9) increased the tension of the tissue(139.8±18.6%, mean ±S.D.) and decreasing external pH(pH 7.4→6.4) decreased
it(72.5±8.4%,
mean±S.D.). Using whole-cell mode of patch clamp techniques, outward currents elicited by depolarizing voltage steps beyond -20mV recorded.
This outward current exhioited properties of outward rectification and oscillation. And this current had no time-dependent decay. The outward currents sensitive to external Ca2+ and Ca2+ channel blocker Cd2+(2mM) and were blocked by external
tetraethylammonium (TEA). But 4-aminopyridine(4-AP) did not reduce the outward current. From these results suggest Ca2+-activated K+ current contributed to the outward current.
Changes in external pH(pH 6.4~7.9) strongly affected the amplitude of the Ca2+-activated K+ current. An increases of external pH from 7.4 to 7.9 produced an increases the amplitude of the outward current. Acidification to 6.4 reduced the outward
current
in a pH-dependent manner.
The above results suggested that the effects of a change of a external pH on vascular smooth muscle tone are mediated via a change of Ca2+-activated K+ currents in the rabbit portal vein.
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