Apparent irrelevance of cyclic nucleotides to the relaxation of tracheal smooth muscle induced by theophylline

Autor: Kolbeck, R. C., Speir, W. A., Carrier, G. O., Bransome, E. D.
Zdroj: Lung; December 1979, Vol. 156 Issue: 1 p173-183, 11p
Abstrakt: The mechanism of action of the negative inotropic (relaxing) effect of the methylxanthine theophylline on respiratory smooth muscle is generally assumed to involve inhibition of cyclic nucleotide phosphodiesterase. When guinea pig tracheal rings or dog tracheal muscle strips were incubated with low concentrations of theophylline capable of producing a significant negative inotropic effect in vivo and in vitro, there was no alteration of cyclic 3′,5′-adenosine monophosphate (cAMP) or cyclic 3′,5′-guanosine monophosphate (cGMP) levels.45Ca uptake increased however, and there was a subcellular redistribution of elemental calcium consistent with a sequestration of calcium in mitochondria and a decrease of myoplasmic calcium ion (Ca++) concentration.
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