Contractil effect of ouabain on tracheal smooth muscle
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Our aim was to characterize the contractil effect of ouabain on tracheal smooth muscle of guinea-pig. For this purpose tracheal rings without epithelium were mounted in an Eckers transducer and placed in a 500 n1 chamber for isometric tension recording. Ouabain (10-4 M), a well known specific inhibitor of the Na-K ATPase (sodium pump), produces a transient contraction that is 94.73±5.65%25 (n=6) of that produced by KC1 (80 mM). The voltage-dependent calcium channel blocker verapamjl (10-4 M) inhibited the contractions induced by ouabain both under normal (33.56±8.41%25, n=6) and depolarizing (56.33±4.6%25, n=6) conditions. Dichlorobenzamil (DCB, 20 μM) a non-specific sodium/calcium exchanger blocker, reduced the contraction induced by ouabain (61.32±3.18%25, n=4). Also, we have some preliminary results that show an inhibitory effect of the acetilcholine antagonist atropine (30 μM) on the ouabain effect. Our conclusions support the idea that ouabain produces a contraction which is partially dependent on the release of acetilcholine, the opening of the voltage dependent calcium channels and the activity of the sodiumcalcium exchanger. Supported by FAIUASLP C95-FAI-01-4.4 to R.E.T.
