AJP - Heart and Circulatory Physiology, Vol 243, Issue 4 551-H559, Copyright © 1982 by American Physiological Society
Na+-K+ exchanges in canine arterial and venous smooth muscle
J. G. De Mey and P. M. Vanhoutte
The effect of altering active sodium transport was compared in the
denervated canine femoral artery and saphenous vein, which respond
differently to a variety of humoral and physical stimuli. Potassium removal
and ouabain caused contractions that were larger in the vein than in the
artery. Activation of sodium transport, by exposing sodium-loaded
preparations to potassium, caused transient ouabain-sensitive relaxations
in both blood vessels; depending on the contractile agonist used, this
relaxant effect was comparable (BaCl2) in both preparations or was larger
(norepinephrine) in the artery than in the vein. In both the artery and the
vein, potassium-induced relaxations were larger during contractions evoked
by BaCl2 than those caused by norepinephrine. In the vein, contractions
caused by acetylcholine were inhibited by potassium to the same extent as
those caused by BaCl2. These results 1) are compatible with a contribution
of sodium transport mechanism to the control of cell membrane permeability
for extracellular calcium in vascular smooth muscle; 2) suggest that active
sodium-calcium exchanges are functionally more important in venous than in
arterial smooth muscle; and 3) illustrate that the heterogeneous behavior
of vascular smooth muscle of different anatomic origins reflects
differences in excitation-contraction coupling.
