Calcium concentration-dependent mechanisms through which ketamine relaxes canine airway smooth muscle.
Anesthesiology
; 86(5): 1104-11, 1997 May.
Article
em En
| MEDLINE
| ID: mdl-9158360
ABSTRACT
BACKGROUND:
Ketamine is a potent bronchodilator that, in clinically used concentrations, relaxes airway smooth muscle in part by a direct effect. This study explored the role of calcium concentration (Ca2+) in this relaxation.METHODS:
Canine trachea smooth muscle strips were loaded with the fluorescent probe fura-2 and mounted in a spectro-photometric system to measure force and intracellular calcium concentration ([Ca2+]i) simultaneously. Calcium influx was estimated using a manganese quenching technique. Cyclic nucleotides in the airway smooth muscle strips were measured by radioimmunoassay.RESULTS:
In smooth muscle strips stimulated with submaximal (0.1 microM) and maximal (10 microM) concentrations of acetylcholine, ketamine caused a concentration-dependent decrease in force and [Ca2+]i. The sensitivity of the force response to ketamine significantly decreased as the intensity of muscarinic receptor stimulation increased; the median effective concentration for relaxation induced by ketamine was 59 microM and 850 microM for tissue contracted by 0.1 microM or 10 microM acetylcholine, respectively (P < 0.05). In contrast, the sensitivity of the [Ca2+]i response did not depend on the intensity of muscarinic receptor stimulation. Ketamine at 1 mM significantly inhibited calcium influx. Ketamine did not significantly increase cyclic nucleotide concentrations.CONCLUSIONS:
Ketamine-induced relaxation of canine airway smooth muscle is associated with a decrease in [Ca2+]i and calcium influx, effects that are not mediated by an increase in cyclic nucleotides; and the sensitivity of the force response to ketamine decreases as the level of preexisting muscle tone increases, an effect that is not explained by differential effects on [Ca2+]i.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Broncodilatadores
/
Cálcio
/
Ketamina
/
Anestésicos Dissociativos
/
Músculo Liso
Limite:
Animals
Idioma:
En
Revista:
Anesthesiology
Ano de publicação:
1997
Tipo de documento:
Article
País de afiliação:
Estados Unidos