Amiodarone improves cardiac sympathetic nerve function to hold norepinephrine in the heart, prevents left ventricular remodeling, and improves cardiac function in rat dilated cardiomyopathy.
BACKGROUND
It is unclear how amiodarone therapy exerts its effects on left ventricular remodeling and cardiac sympathetic nerve function in chronic heart failure. We investigated long-term effects of amiodarone on rat dilated cardiomyopathy after healing of cardiac myosin-induced autoimmune myocarditis.


RESULTS
Rats were treated with oral amiodarone or vehicle for 6 weeks. We determined cardiac function, left ventricular remodeling, and cardiac sympathetic nerve function with iodine-125-labeled metaiodobenzylguanidine ([I125]MIBG). Amiodarone treatment improved left ventricular pressure, central venous pressure, and rate of isovolumetric contraction and decreased ventricular weight (P<0.005). Expression of cytokine mRNA was unchanged; expression of atrial natriuretic peptide, collagen III, and transforming growth factor-beta1 mRNA was decreased in amiodarone-treated rats (P<0.05). Phenotype of myosin heavy chain was moved toward that of normal rats by amiodarone. Initial myocardial uptake of MIBG decreased by 67% (P<0.001) and washout rate accelerated by 221% in rats with chronic heart failure compared with normal rats. Whereas amiodarone decreased the initial uptake by 71% in normal rats, amiodarone decelerated the early washout and the late washout and improved the late myocardial distribution of MIBG in rats with chronic heart failure (257% compared with vehicle-treated rats with chronic heart failure; P<0.01). In proportion to MIBG distributions, cardiac tissue catecholamines were increased by amiodarone treatment.


CONCLUSIONS
Long-term amiodarone treatment prevented left ventricular remodeling and improved cardiac function in rat dilated cardiomyopathy. Long-term amiodarone treatment also restored cardiac sympathetic tone to hold norepinephrine in the heart.
Tachikawa
Hitoshi
H
First Department of Internal Medicine, Niigata University Graduate School of Medicine, Asahimachi 1-754, Niigata 951-8510, Japan. TachiHH@aol.com
Kodama
Makoto
M
Watanabe
Kenichi
K
Takahashi
Toshihiro
T
Ma
Meilei
M
Kashimura
Takeshi
T
Ito
Masahiro
M
Hirono
Satoru
S
Okura
Yuji
Y
Kato
Kiminori
K
Hanawa
Haruo
H
Aizawa
Yoshifusa
Y
D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics; D000638:Amiodarone / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002311:Cardiomyopathy, Dilated / Q000188:drug therapy*; D016207:Cytokines / Q000235:genetics; D004195:Disease Models, Animal; D006321:Heart / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D006334:Heart Function Tests; D008297:Male; D009205:Myocarditis / Q000150:complications; D009206:Myocardium / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000187:drug effects; D051381:Rats; D011917:Rats, Inbred Lew; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology; D020257:Ventricular Remodeling / Q000187:drug effects*
D016207:Cytokines; D012333:RNA, Messenger; D019797:3-Iodobenzylguanidine; D000638:Amiodarone; D009638:Norepinephrine