Perivascular Potassium and pH as Determinants of Local Pial Arterial Diameter in Cats

Abstract

The effects of and the interaction between local perivascular variation in potassium and bicarbonate concentration on the diameter of pial arteries were studied in cats by the microapplication technique. At 11 mEq/liter of bicarbonate, a direct correlation existed between vascular diameter and K⁺ concentrations between 0 and 10 mEq/liter. At K⁺ concentrations between 10 and 20 mEq/liter, no further increase in vascular diameter was observed. At a K⁺ concentration of 5 mEq/liter, an inverse relationship existed between pial arterial diameter and perivascular bicarbonate concentrations between 0 and 22 mEq/liter. At K⁺ concentrations of 0 and 10 mEq/liter, the pial arterial diameter was determined strongly by the K⁺ concentration and was only slightly, if at all, influenced by bicarbonate concentrations between 5 and 22 mEq/liter. At lower bicarbonate concentrations the local acidity induced a marked vasodilation. The results indicate that the diameter of pial arterioles in cats is affected by periarteriolar concentrations of K⁺ and H⁺; the degree of the vasoreaction induced by H⁺ is modulated by K⁺.