AJP - Regulatory, Integrative and Comparative Physiology, Vol 247, Issue 1 100-R105, Copyright © 1984 by American Physiological Society
A comparative study of potassium-induced relaxation in vascular smooth muscle of tiger salamanders and rats
G. M. Malvin and R. C. Webb
This study compares potassium-induced relaxation in vascular tissue of an
amphibian (Ambystoma tigrinum) and a mammal (rat). Aortas (salamanders) and
tail arteries (rats) were cut into helical strips for isometric force
recording. After norepinephrine-induced contraction in potassium-free
solution, arteries relaxed in response to added potassium (1-20 mmol/l).
Potassium-induced relaxation was greater in rat tail arteries than in
salamander aortas. Half-maximal relaxation occurred at a potassium
concentration of approximately 3 mmol/l in both species. Ouabain inhibited
potassium-induced relaxation; salamanders were more sensitive to the
glycoside than rats. Potassium-induced relaxation decreased as the
temperature of the bathing medium was lowered; half-maximal inhibition
occurred at 19 and 29 degrees C for salamander aortas and rat tail
arteries, respectively. Potassium-induced relaxation also varied with the
interval in potassium-free solution, the hydrogen ion concentration (rats
only), and the magnitude of norepinephrine-induced contraction. It appears
that the cellular mechanism causing potassium-induced relaxation is similar
in blood vessels of salamanders and rats. The observations are consistent
with the hypothesis that stimulated electrogenic sodium transport produced
membrane hyperpolarization and relaxation in vascular smooth muscle.
