Document Detail

Consequences of thyroxine treatment on diaphragm and EDL of normal and dystrophic hamsters.
MedLine Citation:
PMID:  15213735     Owner:  NLM     Status:  MEDLINE    
Previously administration of thyroxine (T4) to dystrophic hamsters improved ventilation and slowed the progression of the disease. We hypothesized that the normalization of ventilation in these animals was due to T4 improving structural and functional characteristics of the diaphragm. In the present study, contractile characteristics of the diaphragm and the extensor digitorum longus (EDL) from normal and dystrophic hamsters were evaluated after two months of T4 treatment. Compared to their placebo-treated counterparts, diaphragms and EDLs of T4-treated normal hamsters showed increased optimal muscle lengths and twitch tension, decreased contraction times and increased fatigability. T4-treatment in dystrophic hamsters showed only an increase in diaphragmatic twitch tension development. Force-frequency curves before treatment were generally higher for the normal compared to dystrophic diaphragms and EDLs. T4 administration only increased the force in normal diaphragms at the lower frequencies and in the EDLs at the higher frequencies. Although T4 serum levels were increased in both T4-treated groups, triiodothyronine (T3) was much lower in the dystrophic compared to normal hamsters, suggesting that conversion of T4 to T3 was reduced in dystrophic hamsters. We conclude that the limited functional changes in the diaphragms of T4-treated dystrophic hamsters cannot account for the marked improvement in ventilation previously reported.
Yadhu N Singh; Evelyn H Schlenker; Brahma N Singh; James A Burbach
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Publication Detail:
Type:  Comparative Study; In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Canadian journal of physiology and pharmacology     Volume:  82     ISSN:  0008-4212     ISO Abbreviation:  Can. J. Physiol. Pharmacol.     Publication Date:  2004 May 
Date Detail:
Created Date:  2004-06-23     Completed Date:  2005-01-19     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0372712     Medline TA:  Can J Physiol Pharmacol     Country:  Canada    
Other Details:
Languages:  eng     Pagination:  345-52     Citation Subset:  IM    
Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State University, Brookings 57007-0099, USA.
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MeSH Terms
Diaphragm / drug effects*,  physiology
Muscle Contraction / drug effects*,  physiology
Muscular Dystrophy, Animal / drug therapy*,  physiopathology
Thyroxine / pharmacology,  therapeutic use*
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