AJP - Regulatory, Integrative and Comparative Physiology, Vol 241, Issue 3 228-R232, Copyright © 1981 by American Physiological Society
Systemic arterial pressor responses induced by potassium in dogfish, Squalus acanthias
D. F. Opdyke, R. G. Carroll and N. E. Keller
Intravascular injection of small doses of potassium (0.025-0.5 meq) into
dogfish results in dose-related dorsal aortic pressor responses. The
responses are blocked by phentolamine, an alpha-adrenergic blocking agent.
Assays of plasma catecholamines before and after injection of potassium
(K+) showed that plasma levels of epinephrine (E) and norepinephrine (NE)
had increased significantly (E, 314%; NE, 233%) 1 min after injection. The
pressor responses were initiated 40-90 s after K+ injection at which time
plasma E and NE levels were already significantly elevated. Experiments on
isolated dogfish arterial strips showed that phentolamine cannot block the
increase in vascular smooth muscle tension that occurs after direct
exposure to small increases (0.003 meq/ml) in K+ concentration. Because
phentolamine effectively blocks the pressor response to even higher doses
of K+ in vivo, it is thought that, in addition to any direct
vasoconstrictor effect or K+, the adrenergic stimulation provided by
catecholamine release is required to produce the observed pressor response.
