Document Detail

Direct effects of meconium on rat tracheal smooth muscle tension in vitro.
MedLine Citation:
PMID:  8888287     Owner:  NLM     Status:  MEDLINE    
Increased airway resistance is a component of the meconium aspiration syndrome. Experiments were done to determine whether meconium can have a direct affect on tracheal smooth muscle tension. Tracheal segments (4-5 mm long) were isolated from male Sprague-Dawley rats and suspended in organ baths with physiologic salt solution at 37 degrees C gassed with 95% O2-5% CO2. Each segment was attached to a fixed glass rod on one side and to a force displacement transducer on the other side to measure transverse tension. The segments were stretched to 1.5 g of tension and equilibrated for 2-5 h. Human meconium was diluted in physiologic salt solution (20 g/100 mL) and filtered through gauze. Tension was generated in the segments by adding acetylcholine (10(-6) M) to the tissue bath. Addition of meconium to the organ bath (0.1-5 mg/mL) caused tracheal smooth muscle relaxation in 44% of tracheal segments tested. Contraction occurred in 8% of tested segments, but only at the intermediate and low doses. The amount of relaxation increased significantly in a concentration-dependent manner. These responses were not affected by pretreating segments with indomethacin, removing the tracheal epithelium, using KCl to generate tone, or by heating meconium above 60 degrees C for 1 h. Addition of oleic acid to the organ bath (3.5 x 10(-6) to 3.5 x 10(-4) M) caused concentration-dependent tracheal smooth muscle responses (with relaxation predominating at 3.5 x 10(-4) M and contraction predominating at 3.5 x 10(-6) M). These results suggest that meconium can cause tracheal smooth muscle relaxation by a mechanism that does not appear to be mediated by cyclooxygenase products, by the tracheal epithelium, or a protein. The direct action of meconium on tracheal smooth muscle, which may in part be mediated by a fatty acid, does not appear to contribute significantly to the increased airway tone associated with the meconium aspiration syndrome.
L C Collins; A M Roberts; T W Robinson; I G Joshua
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Pediatric research     Volume:  40     ISSN:  0031-3998     ISO Abbreviation:  Pediatr. Res.     Publication Date:  1996 Oct 
Date Detail:
Created Date:  1997-02-18     Completed Date:  1997-02-18     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0100714     Medline TA:  Pediatr Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  587-91     Citation Subset:  IM    
Department of Internal Medicine, Louisville Veterans Administration Medical Center, Kentucky 40292, USA.
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MeSH Terms
Acetylcholine / pharmacology
Infant, Newborn
Mucous Membrane / physiology
Muscle Contraction* / drug effects
Muscle, Smooth / physiology*
Rats, Sprague-Dawley
Time Factors
Trachea / physiology*
Reg. No./Substance:

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