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.

Attenuated Vasodilator Responses to K+ in Essential Hypertensive Men

“…limb, rather than a response to systemic effects of the ion (3,19). It is likely that the response we observed is, at least in part, independent of local neural structures (20), because in the dog the response is not blocked by phentolamine or nerve section (3). Furthermore, the response is observed in vitro and is not blocked by tetrodotoxin (18).…”

“…In man the vasodilation is not attributable to release of histamine, acetylcholine, or to betaadrenergic stimulation (4). limb, rather than a response to systemic effects of the ion (3,19). It is likely that the response we observed is, at least in part, independent of local neural structures (20), because in the dog the response is not blocked by phentolamine or nerve section (3).…”

“…The KCI infusions do not change limb concentrations of calcium or magnesium; hence, the decrease in limb resistance is probably not an effect of induced changes in these other vasoactive ions. Previous studies indicate that the response is to the potassium rather than to the chloride ion (3).…”

“…Modest increases in the potassium concentration of plasma evoke vasodilation in several vascular beds of men and animals (1)(2)(3)(4)(5)(6)(7). This effect is probably related to the critical role played by potassium ion in the excitation processes of vascular smooth mnuscle cells (8).…”

My forty-three years with in situ small and large blood vessels.

“…We reported in 1959 and 1960 that potassium, 21 sodium, 22 and magnesium, 22 infused intrabrachially at rates that raise local plasma concentrations over physiological ranges, produce small vessel dilation in the dog forelimb; conversely, calcium 22 produces small vessel constriction (after presenting these data to the Council for High Blood Pressure Research in Cleveland, I was seated beside Carl Wiggers at lunch who in a very fatherly way encouraged me to continue this line of investigation). The sodium effect results from increase in osmolality; we and others later showed sodium has no effect independent of that due to hypertonicity.…”