AJP - Heart and Circulatory Physiology, Vol 234, Issue 4 404-H411, Copyright © 1978 by American Physiological Society
Mechanical responses of isolated dog cerebral arteries to reduction of external K, Na, and Cl
N. Toda
Reduction of the extracellular potassium concentration ([K+]0) caused a
significant contraction in helical strips of dog cerebral arteries, but
only a slight contraction, or none, in peripheral (coronary, mesenteric,
renal, and femoral) arteries. The cerebroarterial contraction was abolished
by treatment with ouabain or by substitution of Li+ for Na+, and suppressed
by exposure to Ca2+-free media or verapamil. When one-half of the NaCl of
the bathing solution was substituted with choline chloride a moderate,
sustained contraction was produced in cerebral and peripheral arteries.
Ouabain potentiated this contraction, whereas exposure to Ca2+-free media
abolished it. Substitution of Na propionate, NaI, or Na acetylglycinate for
one-half of the NaCl elicited a marked, transient contraction in only the
cerebral arteries. This contractile response was potentiated by ouabain and
markedly attenuated by exposure to Ca2+-free media. It may thus be
concluded that cerebroarterial contractions induced by a reduction in [K+]0
are due to inhibition of the electrogenic Na+ pump, which results in
depolarization of smooth muscle cells. Substitution of Cl- with less
permeant anions appears to produce cerebroarterial contraction in
association with depolarization of smooth muscle cells.
