Effect of aminophylline-Ca2+ blocker interaction on membrane potential of rat diaphragm fibers.
J Appl Physiol (1985)
; 74(6): 2745-9, 1993 Jun.
Article
em En
| MEDLINE
| ID: mdl-8365976
We studied the antagonism between aminophylline and two calcium channel blockers, nifedipine and verapamil, and its effect on the resting membrane potential of rat diaphragm fibers in vitro at 25 degrees C. Aminophylline hyperpolarizes the fibers in a dose-dependent manner, and the maximum effect is reached with 1 mM of the drug, approximately 9 mV compared with normal values. Both nifedipine and verapamil (1-5 microM) decreased the amount of hyperpolarization induced by aminophylline, and this is partially reversed when the xanthine concentration in the bath is increased. From the Hill equation we obtained a value of 2 for the slope, suggesting that two molecules of aminophylline bind to the receptor. Nifedipine modifies the affinity and the intrinsic activity of aminophylline, whereas verapamil reduces its intrinsic activity. The effect of nifedipine and verapamil is explained on the basis of the changed action of aminophylline on its site as a result of the interaction of the calcium channel blockers with their interdependent receptors.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Diafragma
/
Nifedipino
/
Verapamil
/
Aminofilina
Limite:
Animals
Idioma:
En
Revista:
J Appl Physiol (1985)
Assunto da revista:
FISIOLOGIA
Ano de publicação:
1993
Tipo de documento:
Article
País de afiliação:
Argentina
País de publicação:
Estados Unidos