Upregulated expression of cardiac endothelin-1 participates in myocardial cell growth in Bio14.6 Syrian cardiomyopathic hamsters

OBJECTIVES The purpose of this study is to investigate the role of endogeno us endothelin-1 (ET-1) in myocardial growth in Bio 14.6 Syrian cardiomyopat hic hamsters (Bio). BACKGROUND While ET-1, as a growth-promoting peptide, has been implicated i n the development of secondary cardiac hypertrophy, the role of endogenous ET-1 in cardiac growth in primary myocardial disease is unknown. METHODS We measured left ventricular ET-1 levels by a specific sandwich enz yme-linked immunosorbent assay. Furthermore, we examined the chronic effect of T0201, an ET type A receptor-specific antagonist. RESULTS The ET-1 levels in the left ventricles were 1.8-fold higher (p < 0. 0005) at 20 weeks and 6.4-fold higher (p < 0.0001) at 35 weeks in the Bio c ompared to age-matched control F1B hamsters (F1B). The Bio ET-1 levels in t he lungs exhibited an only 1.3-fold elevation at 35 weeks. Immunohistochemi stry demonstrated the localization of ET-1 mainly in the cardiac myocytes. The treatment with T0201 significantly reduced the heart weight/body weight ratio in the Bio, but did not affect the heart weight/body weight ratio in the F1B. Histologically, T0201 reduced the myocyte diameter of Bio to a le vel similar with that of F1B. However, T0201 did not affect the extent of f ibrosis in Bio or F1B. CONCLUSIONS The ET-1 level in the heart of cardiomyopathic hamsters increas es in stage-dependent and organ-specific manners. Though myocyte degenerati on and subsequent replacement fibrosis do not require an ET-1 pathway, the accelerated synthesis of ET-1 in the heart may contribute to the pathologic al growth of remaining myocytes in this animal model. (C) 1999 by the Ameri can College of Cardiology.