Effect of H+ and elevated PCO
2on membrane electrical properties of rat cerebral arteries |
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Authors: | David R Harder |
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Institution: | (1) College of Medicine, Department of Physiology and Biophysics, University of Vermont, 05405 Burlington, Vermont, USA |
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Abstract: | Some membrane electrical properties of muscle cells from the middle cerebral artery of the rat were recorded with intracellular microelectrodes. The resting membrane potential (E
m) of this preparation was –63 mV. Reduction of extracellular pH to 7.0 in the face of a constantP
CO
2of 40 mm Hg had no significant effect onE
m. Similarly the slope of the steady-state voltage/current curves was not different at pH 7.0 compared to control at pH 7.4. In marked contrast, whenP
CO
2was elevated to around 60 to 70 mm Hg there was a rapid hyperpolarization and reduction in the slope of the voltage current curve suggesting an increased conductance for one or more ionic species. In addition elevation ofP
CO
2increased the slope of theE
m vs. logK]0 curve from 46 mV/decade to 59 m V/decade which is in good agreement with a Nernstian potential for a K+ selective membrane. These data suggest that while the smooth muscle cells of rat cerebral arteries are relatively insensitive to a small reduction in extracellular pH; reduction of intracellular pH by elevatingP
CO
2induces hyperpolarization by increasing K+ conductance (g
k). However, it is not clear from these experiments if theP
CO
2effects are mediated entirely by changes in pH or if there is a direct membrane action of CO2.This work is supported by Grant no. HL27862 |
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Keywords: | Rat middle cerebral artery pH P
CO
2 Membrane potential K+ conductance |
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