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Endogenous nitric oxide modulation of potassium‐induced changes in guinea‐pig airway tone
Author(s) -
Folkerts Gert,
Linde Henk,
Verheyen Alfons K.C.P.,
Nijkamp Frans P.
Publication year - 1995
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1995.tb15024.x
Subject(s) - contraction (grammar) , chemistry , trachealis muscle , potassium , guinea pig , epithelium , biophysics , nitric oxide , depolarization , muscle contraction , respiratory epithelium , endocrinology , medicine , potassium channel , biology , pathology , organic chemistry
1 An experimental set up is used whereby the serosal (out)side or mucosal (in)side of the guinea‐pig isolated tracheal tube can be stimulated selectively with drugs and reactivity measured. 2 Potassium induces a concentration‐dependent (5 − 70 mM) monophasic contraction of tracheal tubes when added on the outside. In contrast, on the inside, potassium induces a concentration‐dependent relaxation at low concentrations (5–40 mM) which was reversed into a contraction up to approximately basal tone at higher concentrations (50–70 mM). 3 Epithelium denudation reversed the potassium‐induced relaxation into a contraction. Interestingly, in the ‘half epithelium‐denuded trachea the contractions were significantly ( P <0.01) reduced by 46% compared to complete epithelium‐denuded tissues. 4 Incubation with the nitric oxide (NO) synthase inhibitor N Ω ‐nitro‐L‐arginine methyl ester (l‐NAME, 120 μ m ) for 30 min on the inside of the tracheal tube completely prevented the relaxation. However, L‐NAME did not reverse the potassium‐induced relaxation into a contraction. This indicates that potassium does not penetrate through the epithelial layer. 5 It is concluded that depolarization of smooth muscle cells leads to a monophasic contraction and that depolarization of the epithelium leads to a relaxation of tracheal smooth muscle. The epithelial layer has an important barrier function and can release relaxing factors like NO.