Triiodothyronine decreases the accumulation of 1,2-diacylglycerol in rat hearts
Okumura, K.; Matsui, H.; Kikuchi, M.; Mukawa, H.; Toki, Y.; Ito, T.
Canadian Journal of Cardiology 11(7): 565-572
1995
ISSN/ISBN: 0828-282X PMID: 7544686 Document Number: 441003
1,2-Diacylglycerol (DAG) is an intracellular signal mediator that may initiate protein synthesis and cardia hypertrophy via activation of protein kinase C. The amounts of 1,2-DAG and its fatty acid components in the myocardium were assessed and compared with the concentrations of RNA and DNA in cardiac hypertrophy induced by administering triiodothyronine (T-3) with and without cycloheximide, an inhibitor of protein synthesis. After the first injection of T-3 no cardiac hypertrophy was observed, and there were no differences in myocardial 1,2-DAG content or in RNA and DNA concentrations. Cardia hypertrophy was present on days 3 and 7 after a daily injection of T-3. Myocardial RNA concentration was increased by 26% on day 3 and by 34% on day 7, whereas the myocardial 1,2-DAG content was decreased by 8% on day 3 and by 24% on day 7. Pretreatment with cycloheximide of T-3-treated rats prevented the development of cardiac hypertrophy, but elevated the RNA concentration and lowered the 1,2-DAG content compared with the findings in T-3-treated rats. Analysis of the fatty acid components of 1,2-DAG revealed that the amounts of 16:0, 18:1 and 18:2 were decreased, accompanied by an elevation of RNA concentration and a decrease in 1,2-DAG content. It seems that TNA synthesis preceded the alteration in 1,2-DAG. These findings suggest that 1,2-DAG is not involved inthe initiation of cardiac hypertrophy induced by T-3, but is affected by the enhanced concentration of RNA resulting form the introduction of thyroid hormones into the myocardium.