Korean J Physiol Pharmacol.  1998 Dec;2(6):705-714.

Moderate elevation of extracellular K+ concentration induces vasorelaxation in isolated rat, rabbit and human cerebral arteries: Role of Na pump and Ba-sensitive process

• Kim DH
• Kim SJ
• Lee SJ
• Park SJ
• Kim KW

Abstract

Cerebral blood vessels relax when extracellular K+ concentrations ((K+))e are elevated moderately (2~15 mM, K+-induced vasorelaxation). We have therefore studied the underlying mechanism for this K+-induced vasorelaxation in the isolated middle cerebral arteries (MCAs). The effects of ouabain and Ba2+ on K+-induced vasorelaxation were examined to determine the role of sodium pump and/or Ba-sensitive process (possibly, inward rectifier K current) in the mechanism. Mulvany myograph was used to study 24 rats, 18 rabbits, and 10 humans MCAs (216+/-3 mum, 347+/-7 mum, and 597+/-39 mum in diameter when stretched to a tension equivalent to 55 mmHg). High K+ (125 mM) and PGF2alpha (1~10 muM) induced concentration-dependent contractions in all 3 species, while histamine (10~50 muM) evoked contraction only in the rabbits and induced relaxation in the rats and humans. Addition of K+ (2~10 mM) to the control solution induced vasorelaxations. These effects were inhibited by the pretreatment with both ouabain (10 muM) and Ba2+ (0.1~0.3 mM) in the rat, but only with ouabain (10 muM) in the rabbit and human. These results suggest that K+-induced vasorelaxation occurs via the stimulation of electrogenic Na pump in the rabbit and human MCAs, while in the rat MCAs via the activation of both Na pump and Ba-sensitive process.

Keyword

Cerebral artery; Vasorelaxation; Myograph; Potassium; Ouabain; Barium

MeSH Terms

Animals
Barium
Blood Vessels
Cerebral Arteries*
Dinoprost
Histamine
Humans*
Middle Cerebral Artery
Ouabain
Potassium
Rabbits
Rats*
Relaxation
Sodium-Potassium-Exchanging ATPase
Vasodilation*
Barium
Dinoprost
Histamine
Ouabain
Potassium
Sodium-Potassium-Exchanging ATPase