MgSO4 relaxes porcine airway smooth muscle by reducing Ca2+ entry

David Kumasaka, Karen Sue Lindeman, Judith Clancy, Boris Lande, Thomas L. Croxton, Carol A. Hirshman

Research output: Contribution to journalArticle

Abstract

Magnesium sulfate (MgSO4) is used clinically, but its mechanism of action is unknown. To determine whether MgSO4 relaxes airway smooth muscle and to investigate the pathways involved, we compared effects of MgSO4 in porcine tracheal and bronchial muscles contracted with either carbachol or KCl and measured the effects of MgSO4 on the concentration of intracellular free calcium ([Ca2+]i). Lungs were dissected after anesthesia and exsanguination. Tracheal strips and bronchial rings were suspended in tissue baths for measurement of isometric tension in the presence of different concentrations of MgSO4. In separate experiments, tracheal smooth muscle tension and [Ca2+]i were measured simultaneously, using the fluorescent dye fura 2. MgSO4 (1.2, 2.2, 9.2 mM) produced a concentration-dependent rightward shift of contraction dose-response curves to KCl but not to carbachol. MgSO4 relaxed trachealis muscles precontracted with KCl or carbachol and simultaneously decreased [Ca2-]i. These findings indicate that MgSO4 directly relaxes airway smooth muscle and that the mechanism involves a decrease in [Ca2+]i. Because initiation and maintenance of contraction during KCl stimulation and maintenance of contraction during carbachol stimulation require Ca2+ entry through voltage-dependent calcium channels, MgSO4-induced relaxation may involve a decrease in Ca2+ entry via these channels.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume270
Issue number3 14-3
StatePublished - Mar 1996

Fingerprint

Carbachol
Smooth Muscle
Swine
Maintenance
Exsanguination
Muscles
Magnesium Sulfate
Muscle Tonus
Fura-2
Calcium Channels
Baths
Fluorescent Dyes
Anesthesia
Calcium
Lung

Keywords

  • Bronchodilation
  • Carbachol
  • Fura 2
  • Potassium chloride

ASJC Scopus subject areas

  • Cell Biology
  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)

Cite this

MgSO4 relaxes porcine airway smooth muscle by reducing Ca2+ entry. / Kumasaka, David; Lindeman, Karen Sue; Clancy, Judith; Lande, Boris; Croxton, Thomas L.; Hirshman, Carol A.

In: American Journal of Physiology - Lung Cellular and Molecular Physiology, Vol. 270, No. 3 14-3, 03.1996.

Research output: Contribution to journalArticle

Kumasaka, David ; Lindeman, Karen Sue ; Clancy, Judith ; Lande, Boris ; Croxton, Thomas L. ; Hirshman, Carol A. / MgSO4 relaxes porcine airway smooth muscle by reducing Ca2+ entry. In: American Journal of Physiology - Lung Cellular and Molecular Physiology. 1996 ; Vol. 270, No. 3 14-3.
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