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Am J Physiol Heart Circ Physiol 279: H351-H360, 2000;
0363-6135/00 $5.00
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Vol. 279, Issue 1, H351-H360, July 2000

Sodium-potassium-ATPase electrogenicity in cerebral precapillary arterioles

K. Quinn, C. Guibert, and D. J. Beech

School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom

Electrogenicity of the Na+/K+ pump has the capability to generate a large negative membrane potential independently of ion-channel current. The high background membrane resistance of arterioles may make them susceptible to such an effect. Pump current was detected by patch-clamp recording from smooth muscle cells in fragments of arterioles (diameter 24-58 µm) isolated from pial membrane of rabbit cerebral cortex. The current was 20 pA at -60 mV, and the extrapolated zero current potential was -160 mV. Two methods of estimating the effect of pump electrogenicity on resting potential indicated an average contribution of -35 mV. In 20% of the recordings, block of inward rectifier K+ channels by 10-100 µM Ba2+ led to a small depolarization, but hyperpolarization was a more common response. Ba2+ also inhibited depolarization evoked by 20 mM K+. In arterioles within intact pial membrane, Ba2+ failed to evoke constriction but inhibited K+-induced constriction. The data suggest that cerebral arterioles are vulnerable to the hyperpolarizing effect of the Na+/K+ pump, excessive effects of which are prevented by depolarizing inward rectifier K+ current

blood vessel; artery; cerebral circulation; inward rectifier potassium ion current.


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