EFFECTS OF CILAZAPRIL AND VERAPAMIL ON MYOCARDIAL IODINE-125-METAIODOBENZYLGUANIDINE ACCUMULATION IN CARDIOMYOPATHIC BIO-53.58 HAMSTERS

Sympathetic nervous system activation is important in the pathophysiol ogy of congestive heart failure. However, little about how the treatme nt for heart failure may influence myocardial sympathetic nervous acti vity has been established. In this study, we evaluated effects of cila zapril (CLZ) and verapamil (VER) on myocardial sympathetic nervous act ivity in cardiomyopathic BIO 53.58 hamsters using [I-125]metaiodobenzy lguanidine ([I-125]MIBG). Methods: We used BIO 53.58 hamsters aged 3, 6 and 10 mo and age-matched normal F1b hamsters. We divided BIO 53.58 hamsters into untreated, CLZ- and VER-treated groups. We measured myoc ardial [I-125]MIBG uptakes and norepinephrine concentrations and evalu ated the extent of fibrosis and the distribution of [I-125]MIBG. Resul ts: The myocardial [I-125]MIBG uptake was significantly lower in BIO 5 3.58 hamsters aged 6 and 10 mo than in age-matched F1b hamsters. Myoca rdial [I-125]MIBG uptake was significantly correlated to myocardial no repinephrine concentration in BIO 53.58 hamsters. Myocardial [I-125]MI BG uptake was significantly higher in both of the treated groups than in the untreated group. The extent of myocardial fibrosis was signific antly lower in both of the treated groups than in the untreated group, The myocardial [I-125]MIBG uptake showed a significant inverse correl ation with the extent of fibrosis. Myocardial [I-125]MIBG distribution was highly heterogeneous in the untreated BIO 53.58 hamsters, whereas it was homogeneous in the F1b hamsters aged 6 mo and the treated BIO 53.58 hamsters. Conclusion: In BIO 53.58 hamsters, myocardial [I-125]M IBG uptake decreased with the progression of cardiomyopathy, and the d ecreased uptake was improved by treatment with CLZ and VER. Thus, myoc ardial [I-125]MIBG uptake can reflect the effects of treatment on card iomyopathy, as well as the progression of cardiomyopathy.