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Ca 2+ ion sequestration by guinea‐pig tracheal cartilage: its influence on trachealis reactivity to KCl
Author(s) -
Gupta Paul,
Markham Anthony,
Morgan Rae M.
Publication year - 1991
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.1476-5381.1991.tb12395.x
Subject(s) - trachealis muscle , chemistry , cartilage , verapamil , calcium , guinea pig , biophysics , anatomy , medicine , endocrinology , biology , charybdotoxin , organic chemistry
1 The contractile response of guinea‐pig isolated trachealis to KCl has been studied in the presence and absence of cartilage. 2 Dissection of cartilage from the trachealis resulted in both a rightward displacement of the concentration‐response curve to KCl (EC 50 value: intact strip, 26.9 ± 3.7 m m n = 5; dissected strip, 38.7 ± 2.6 m m n = 5; P < 0.05), and a reduction in the contractile response to KCl (30 m m ) observed in a nominally Ca 2+ ‐free medium. 3 Removal of cartilage from the trachealis did not alter the responsiveness of the tissue to CaCl 2 (2.5 m m ) when added to K + depolarized tissues. 4 Muscle‐denuded cartilage rings were prepared by surgical removal of the trachealis muscle. Autoradiographic studies, and a direct comparison of Ca 2+ (2.5 m m ) uptake with that of sorbitol (2.5 m m ) showed that cartilage per se had a high capacity to accumulate Ca 2+ ions by a process which was resistant to iodoacetate (100 μ m ), diflunisal (100 μ m ) and boiling. 5 The uptake of 45 Ca into isolated cartilage was unaltered by the addition of orthovanadate (500 μ m ), verapamil (10 μ m ), diltiazem (10 μ m ) or Bay K 8644 (10 μ m ), but was significantly reduced ( P < 0.05) in the presence of LaCl 3 (1–10 m m ). 6 We conclude, like previous studies, that cartilage may supply a pool of Ca 2+ ions to airway smooth muscle during the generation of tension in a noninally Ca 2+ ‐free medium, and that LaCl 3 may provide an experimental tool to elucidate further the role of non‐muscle Ca 2+ ‐depots in smooth muscle contraction.