Cardiac 3,4-dihydroxyphenylethylene glycol (DHPG) and catecholamine levels in a rat model of left ventricular failure

Cardiac norepinephrine (NE), dopamine (DA), epinephrine (Epi), and dihydroxyphenylethylene glycol (DHPG) (a major neuronal metabolite of NE) content were measured in rats with cardiac failure resulting from left ventricular myocardial infarction (LVMI) induced by coronary ligation. The ratio of DHPG/NE was significantly higher in both the right ventricle and inter-ventricular septum of rats with LVMI compared with controls, reflecting a tendency for cardiac DHPG content to rise and NE content to fall during cardiac failure. Cardiac DA and Epi content did not significantly differ between rats with LVMI and controls. Elevated DHPG/NE ratios apparently reflect the increase in NE turnover that accompanies elevated sympathetic activity in heart failure more precisely than changes in NE levels or DHPG levels alone. Furthermore, DHPG/NE ratios are not influenced by increases in cardiac weight due to cardiac hypertrophy. The DHPG/NE ratios may be a useful index of cardiac sympathetic activity for future studies of the effects of drug treatment of cardiac failure in this animal model.