Article date: November 1987
By: Elliott W. Chideckel, James L. Frost, Pamela Mike, Jeffrey S. Fedan in Volume 92, Issue 3, pages 609-614
The Na+, K+‐pump has been implicated in animal models of airway hyperreactivity. We examined the effects of inhibiting the Na+, K+‐pump and Na+, Ca2+‐exchange on isometric tone of isolated trachealis from humans and other species.
In preparations from 5 out of 9 humans, strong spontaneous contractions (36–48 h−1; up to 1.8 g) developed within 25 min.
Ouabain (10−7‐10−5m) caused an immediate and sustained contraction. This response was not blocked by atropine, diphenhydramine, or cimetidine.
Contractions were also elicited when the normal physiological solution was changed to a K+‐free solution, a procedure which inhibits the Na+, K+‐pump, and in reduced (15 mm) Na+ solution, which inhibits Na+, Ca2+ exchange.
In preparations of dog and guinea‐pig isolated trachea, ouabain (10−5m) caused a multiphasic response; in the rabbit, ouabain was without effect. K+‐free solution was without effect in the dog preparations and produced relaxation of the guinea‐pig trachea. Guinea‐pig tracheae responded to a low Na+ solution with a strong contraction.
Our findings indicate that: (a) human airway smooth muscle may be a spontaneously contracting muscle, at least in vitro, (b) a prolonged contraction to ouabain is unique for the human airway smooth muscle among the animals tested, as is the contraction in a K+‐free medium, and (c) the contractile response does not involve acetylcholine or histamine release, but may involve a Na+, Ca2+‐exchange mechanism. These results suggest that the level of Na+, K+‐pump activity could play a role in determining the degree of bronchomotor tone in humans.
The Na+, K+‐pump has been implicated in animal models of airway hyperreactivity. We examined the effects of inhibiting the Na+, K+‐pump and Na+, Ca2+‐exchange on isometric tone of isolated trachealis from humans and other species.
In preparations from 5 out of 9 humans, strong spontaneous contractions (36–48 h−1; up to 1.8 g) developed within 25 min.
Ouabain (10−7‐10−5m) caused an immediate and sustained contraction. This response was not blocked by atropine, diphenhydramine, or cimetidine.
Contractions were also elicited when the normal physiological solution was changed to a K+‐free solution, a procedure which inhibits the Na+, K+‐pump, and in reduced (15 mm) Na+ solution, which inhibits Na+, Ca2+ exchange.
In preparations of dog and guinea‐pig isolated trachea, ouabain (10−5m) caused a multiphasic response; in the rabbit, ouabain was without effect. K+‐free solution was without effect in the dog preparations and produced relaxation of the guinea‐pig trachea. Guinea‐pig tracheae responded to a low Na+ solution with a strong contraction.
Our findings indicate that: (a) human airway smooth muscle may be a spontaneously contracting muscle, at least in vitro, (b) a prolonged contraction to ouabain is unique for the human airway smooth muscle among the animals tested, as is the contraction in a K+‐free medium, and (c) the contractile response does not involve acetylcholine or histamine release, but may involve a Na+, Ca2+‐exchange mechanism. These results suggest that the level of Na+, K+‐pump activity could play a role in determining the degree of bronchomotor tone in humans.
DOI: 10.1111/j.1476-5381.1987.tb11363.x
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