Role of endothelial nitric oxide and smooth muscle potassium channels in cerebral arteriolar dilation in response to acidosis

Tetsuyoshi Horiuchi, Hans H. Dietrich, Kazuhiro Hongo, Tetsuya Goto, Ralph G. Dacey

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

Background and Purpose - Potassium channels or nitric oxide or both are major mediators of acidosis-induced dilation in the cerebral circulation. However, these contributions depend on a variety of factors such as species and vessel location. The present study was designed to clarify whether potassium channels and endothelial nitric oxide are involved in acidosis-induced dilation of isolated rat cerebral arterioles. Methods - Cerebral arterioles were cannulated and monitored with an inverted microscope. Acidosis (pH 6.8 to 7.4) produced by adding hydrogen ions mediated dilation of the cerebral arterioles in a concentration-dependent manner. The role of nitric oxide and potassium channels in response to acidosis was examined with several specific inhibitors and endothelial damage. Results - The dilation was significantly inhibited by potassium chloride (30 mmol/L) and glibenclamide (3 μmol/L; ATP-sensitive potassium channel inhibitor). We found that 30 μmol/L BaCl2 (concentration-dependent potassium channel inhibitor) also affected the dilation; however, an additional treatment of 3 μmol/L glibenclamide did not produce further inhibition. Tetraethylammonium ion (1 mmol/L; calcium-activated potassium channel inhibitor) and 4-aminopyridine (100 μmol/L; voltage-dependent potassium channel inhibitor) as well as ouabain (10 μmol/L; Na-K ATPase inhibitor) and N-methylsulphonyl-6-(2-proparglyloxyphenyl) hexanamide (1 μmol/L; cytochrome P450 epoxygenase inhibitor) did not alter acidotic dilation. Nω-Monomethyl-L-arginine (10 μmol/L) and Nω-nitro-L-arginine (10 μmol/L) as nitric oxide synthase inhibitor blunted the dilation. Furthermore, the dilation was significantly attenuated after the endothelial impairment. Additional treatment with glibenclamide (3 μmol/L) further reduced the dilation in response to acidosis. Conclusions - Endothelial nitric oxide and smooth muscle ATP-sensitive potassium channels contribute to acidosis-induced dilation of rat cerebral arterioles. Endothelial damage caused by pathological conditions such as subarachnoid hemorrhage or traumatic brain injury may contribute to reduced blood flow despite injury-induced cerebral acidosis.

Original languageEnglish
Pages (from-to)844-849
Number of pages6
JournalStroke
Volume33
Issue number3
DOIs
StatePublished - Mar 19 2002

Keywords

  • Acid-base equilibrium
  • Cerebral circulation
  • Hydrogen-ion concentration
  • Microcirculation
  • Rats

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