Effects of K+ channel blockers on the relaxant action of dihydralazine, cromakalim and nitroprusside in isolated rabbit femoral arteries.
Eur J Pharmacol
; 215(2-3): 177-83, 1992 May 14.
Article
em En
| MEDLINE
| ID: mdl-1396985
ABSTRACT
The relaxant responses to dihydralazine and the influence of different K+ channel blockers were studied in isolated rabbit femoral arteries. The prototype K+ channel opener, cromakalim, and nitroprusside, which does not produce relaxation by K+ channel activation were used for comparison. Dihydralazine was most effective on contractions induced by noradrenaline (EC50 = 1.1 microM; Emax = 95%) and relaxed the contractions elicited by 20 mM K+ (EC50 = 2.0 microM; Emax = 81% in preference to 124 mM K(+)-induced contractions (EC50 = 30.1 microM; Emax = 54%). Cromakalim, but not nitroprusside, also selectively relaxed 20 mM K(+)-induced contractions. In noradrenaline-contracted arteries, glibenclamide (10 microM) completely suppressed the relaxant response to cromakalim but did not influence the vasorelaxation produced by dihydralazine or nitroprusside. Tetraethylammonium (8 mM) and Cs+ (4 mM) shifted the concentration-relaxation curve for dihydralazine 2-fold to the right, whereas Ba2+ (0.1 mM), 4-aminopyridine (5 mM) and procaine (0.1 mM) failed to influence dihydralazine-induced responses. Tetraethylammonium (8 mM) shifted the concentration-relaxation curve for cromakalim and nitroprusside 6-fold to the right and suppressed the maximal relaxant effects by about 30%. It is concluded that dihydralazine produces vascular smooth muscle relaxation by a mechanism different from the opening of glibenclamide- and ATP-sensitive K+ channels.
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Base de dados:
MEDLINE
Assunto principal:
Pirróis
/
Vasodilatadores
/
Benzopiranos
/
Nitroprussiato
/
Canais de Potássio
/
Di-Hidralazina
/
Músculo Liso Vascular
Limite:
Animals
Idioma:
En
Revista:
Eur J Pharmacol
Ano de publicação:
1992
Tipo de documento:
Article
País de afiliação:
Dinamarca