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Changes in smooth muscle tone during osmotic challenge in relation to epithelial bioelectric events in guinea pig isolated trachea.

Authors
Dortch-Carnes-J; Van Scott-MR; Fedan-JS
Source
J Pharmacol Exp Ther 1999 May; 289(2):911-917
NIOSHTIC No.
20000955
Abstract
The relationship between epithelial bioelectric events and epithelium-dependent relaxant and contractile responses of airway smooth muscle in response to hyperosmolar and hypo-osmolar solutions was investigated in guinea pig isolated trachea. Tracheae were perfused with normal or nonisosmotic modified Krebs-Henseleit solution while simultaneously monitoring transepithelial potential difference (VT) and contractile and relaxant responses of the muscle. Baseline VT was 10.1 to 13.3 mV (distal and proximal ends, respectively). Intraluminal amiloride (104 M) induced a 3.7-mV depolarization, verifying that the VT was of epithelial origin. Extraluminal methacholine (3 X 10(-7) M; EC50) caused hyperpolarization and smooth muscle contraction; intraluminal methacholine had very little effect. Increasing intraluminal bath osmolarity via addition of 240 mOsM NaCl or KCl caused an immediate and prolonged depolarization and epithelium-dependent relaxation. Increasing intraluminal bath osmolarity with sucrose evoked similar responses, except that an immediate, transient hyperpolarization and contraction preceded the depolarization and relaxation. Increasing extraluminal bath osmolarity with 240 mOsM NaCl induced depolarization and a longer lasting epithelium-dependent relaxation, whereas extraluminally added 240 mOsM KCl induced a complex smooth muscle response (i.e., transient relaxation followed by contraction), which was accompanied by prolonged depolarization. Intraluminal hypo-osmolarity produced a transient hyperpolarization followed by depolarization along with contraction of the smooth muscle. Bioelectric responses always preceded smooth muscle responses. These results suggest that bioelectric events in the epithelium triggered by nonisosmotic solutions are associated with epithelium-dependent responses in tracheal smooth muscle.
Keywords
Trachea; Laboratory-animals; Pulmonary-system-disorders; Epithelial; Asthma; Respiratory; Bioelectric-effects
CODEN
JPETAB
Publication Date
19990501
Document Type
Journal Article
Email Address
jsf2@cdc.gov
Fiscal Year
1999
NTIS Accession No.
NTIS Price
Issue of Publication
2
ISSN
0022-3565
NIOSH Division
HELD
Source Name
Journal of Pharmacology and Experimental Therapeutics
State
WV; NC
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