Relaxant effects of xanthines, a beta 2-receptor agonist and Ca2+ antagonists in guinea-pig tracheal preparations contracted by potassium or carbachol

European Journal of Pharmacology
J E Nielsen-KudskC G Persson

Abstract

Potassium (124 mM K+ Krebs) produced a biphasic contractile response in the guinea-pig isolated trachea. An initial phasic contraction was followed by a larger and sustained contraction. Repeated potassium-induced contractions in spontaneously contracted guinea-pig tracheas were not reproducible. However, reproducible K+ responses were obtained in the presence of indomethacin (10(-6) M) that almost abolished the spontaneous tone. This suggested that endogenous cyclooxygenase products were variably released by K+ and interfered with its contractile effects. Both phases of K+-induced contractions were inhibited in Ca2+-free/EGTA Krebs. In contrast, about 80% of the contractile response to carbachol persisted in this medium. Tracheas contracted by potassium (indomethacin present) were completely relaxed by theophylline and enprofylline but only partly relaxed by terbutaline. All bronchodilators completely relaxed carbachol-contracted preparations. Each bronchodilator was 2-3 times less potent to relax K+- than carbachol-induced contractions. In sharp contrast, two Ca2+ antagonists, verapamil and nimodipine, preferentially relaxed K+-induced contractions. The results obtained with Ca2+ antagonists, which are poorly effective in ast...Continue Reading

References

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Citations

Nov 22, 1988·European Journal of Pharmacology·J E Nielsen-KudskC B Nielsen
Aug 22, 1989·European Journal of Pharmacology·S MellemkjaerC Siggaard
May 16, 1990·European Journal of Pharmacology·J E Nielsen-KudskA M Brønsgaard
Jul 6, 1993·European Journal of Pharmacology·C M PedersenJ E Nielsen-Kudsk
Apr 1, 1996·Journal of Autonomic Pharmacology·M D HerreraE Marhuenda
Aug 1, 1995·British Journal of Pharmacology·G FolkertsF P Nijkamp
Aug 2, 2000·Respiratory Medicine·S Thirstrup
Aug 1, 1988·British Journal of Pharmacology·J S Gillespie, H Sheng
Sep 1, 1995·Journal of Anesthesia·Tat-Leang LeeShan S Ratnam

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