Contractile force and intracellular Ca2+ during relaxation of canine tracheal smooth muscle

S. J. Gunst, S. Bandyopadhyay

Research output: Contribution to journalArticle

19 Scopus citations


Muscle strips loaded with the Ca2+ indicator aequorin were studied in vitro to determine the effects of inhibitory stimuli on force and cytosolic free Ca2+. In muscles contracted isometrically with acetylcholine (ACh), 5-hydroxytryptamine (5-HT), or carbachol, decreases in muscle force caused by isoproterenol (10-5 M) or forskolin (10-5 M) were accompanied by proportional decreases in aequorin luminescence. A similar relationship between decreases in muscle force and aequorin luminescence was observed when muscles were relaxed by stimulating Na+-K+-ATPase activity. These results suggest that the Ca2+ sensitivity of contractile proteins was not decreased during adenosine 3',5'-cyclic monophosphate (cAMP)-dependent relaxation. However, aequorin luminescence did not decrease when muscles contracted by K+ depolarization were relaxed with isoproterenol. Incubation of muscles in forskolin depressed increases in both force and aequorin luminescence in response to 5-HT or ACh. Incubation of muscles in isoproterenol had a similar effect on responses to 5-HT but depressed increases in force without depressing increases in luminescence in response to ACh. Results indicate that under most conditions the reduction of cytosolic Ca2+ plays an important role in the cAMP-dependent relaxation of canine tracheal smooth muscle.

Original languageEnglish (US)
Pages (from-to)26/2
JournalAmerican Journal of Physiology - Cell Physiology
Issue number2
StatePublished - 1989

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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