Regulation of alpha- and beta-myosin heavy chain messenger RNAs in the rat myocardium by amiodarone and by thyroid status.
1. A number of the cardiovascular effects of amiodarone resemble those of hypothyroidism, prompting examination of the relationship between the actions of the drug and thyroid hormones. Amiodarone treatment of the rat was used as a model to determine the influence of the drug on thyroid hormone-regulated gene expression in the myocardium and liver; interactions between amiodarone and thyroid status were examined in hypothyroid and tri-iodothyronine (T3)-treated animals. 2. Myocardial levels of alpha- and beta-myosin heavy chain (MHC) messenger RNAs (mRNAs) were measured by dot hybridization to specific oligonucleotide probes; myocardial actin mRNA was measured in parallel by hybridization to a complementary DNA (cDNA) probe. Hepatic levels of Spot 14 and thyroxine-binding prealbumin mRNA were similarly determined by dot hybridization to radiolabelled cDNAs. 3. Amiodarone treatment of the rat resulted in specific increases in both alpha- and beta-MHC mRNAs in the myocardium, as well as hepatic Spot 14 mRNA, changes reversed by T3 administration. 4. Hypothyroidism resulted in a reduction in myocardial alpha-MHC and hepatic Spot 14 mRNAs, in contrast to amiodarone, whilst hypothyroidism and amiodarone both exerted stimulatory influences on beta-MHC mRNA. Treatment of hypothyroid rats with amiodarone had no significant effect on beta-MHC or Spot 14 mRNAs, but a further reduction in alpha-MHC mRNA, compared with the untreated hypothyroid state, was evident. 5. The demonstrated influence of amiodarone on both alpha- and beta-MHC mRNAs and interactions between amiodarone and thyroid status in regulating MHC gene expression may be relevant to its therapeutic effect in man.
Franklyn
J A
JA
Department of Medicine, University of Birmingham, Queen Elizabeth Hospital, Edgbaston, U.K.
Green
N K
NK
Gammage
M D
MD
Alhquist
J A
JA
Sheppard
M C
MC
D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D005260:Female; D005786:Gene Expression Regulation; D006321:Heart / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014284:Triiodothyronine / Q000494:pharmacology*
D012333:RNA, Messenger; D014284:Triiodothyronine; D009218:Myosins; D000638:Amiodarone