Sodium-potassium-ATPase electrogenicity in cerebral precapillary arterioles.
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 microm) 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 microM Ba(2+) led to a small depolarization, but hyperpolarization was a more common response. Ba(2+) also inhibited depolarization evoked by 20 mM K(+). In arterioles within intact pial membrane, Ba(2+) 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
Quinn
K
K
School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.
Guibert
C
C
Beech
D J
DJ
D000818:Animals; D001160:Arterioles / Q000502:physiology*; D002540:Cerebral Cortex / Q000098:blood supply; D002560:Cerebrovascular Circulation / Q000502:physiology*; D019806:Cromakalim / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D010042:Ouabain / Q000031:analogs & derivatives / Q000494:pharmacology; D010841:Pia Mater / Q000098:blood supply; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D019806:Cromakalim; C000977:dihydroouabain; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium