Effect of potassium on small and large blood vessels of the dog forelimb.

Abstract

Potassium salts were infused into the brachial artery while holding the rate of blood flow constant and measuring pressures at four sites along the length of the bed. Small vessel resistance progressively decreased as a function of infusion rate. Arterial resistance did not change and then increased as a function of infusion rate. The net effect was a decrease and then an increase in total resistance. The decrease was associated with lessened responses to norepinephrine and acetylbetamethylcholine, serum potassium concentrations in the leg up to about 8 mEq/l. and no change of serum concentration in the body as a whole. The increase in resistance was associated with serum concentrations in the leg in excess of 8 mEq/l. and slight elevation of concentrations in the body as a whole. The decrease of small vessel resistance was lessened but still present following denervation of the leg and adrenergic blockade. Arterial resistance did not increase following adrenergic blockade. Those findings indicate that potassium excess dilates arterioles in the dog foreleg by a direct action as well as by decreasing the sensitivity of the arteriole to natural pressor substances. The large arterial constriction may be related to an adrenal discharge.