Changes in perfusion and fatty acid metabolism of rat heart with autoimmune myocarditis

To elucidate the change in perfusion and aerobic metabolism in myocarditis, tissue counting and dual tracer ex vivo autoradiography with Tl-201 and a free fatty acid analog, I-123- or I-125-labeled (p-iodophenyl)-methyl-penta decanoic acid (BMIPP), were performed in rats with myocarditis induced by i mmunization with cardiac myosin. Inflammatory damage was classified histolo gically. At the acute stage (2-4 weeks after the antigen-injection), total heart uptakes of Tl and BMIPP and the ratio (BMIPP/Tl) were significantly r educed in myocarditis rats (N = 15) compared with the controls (N = 12). My ocardial distribution of Tl and BMIPP was not homogeneous. Relative uptake of Tl and BMIPP (N = 9, 128 regions) was gradually decreased with the exten t of inflammation, and the regional BMIPP/Tl was smaller than the control. At the subacute stage (7 weeks after the antigen-injection), total Tl uptak e in myocarditis rats (N = 5) recovered to the control level (N = 4), but t hat of BMIPP was still significantly lower than the control. BMIPP/Tl was s till significantly lower in myocarditis. Myocardial distribution of Tl and BMIPP recovered to be more homogeneous. Relative uptake of Tl and BMIPP (N = 6, 78 regions) still gradually but significantly decreased with the exten t of inflammation. Regional BMIPP/Tl was still depressed in myocarditis. Th ese results indicate that myocardial perfusion and aerobic metabolism were discrepant and heterogeneously suppressed with severe inflammation during t he acute stages, bur the difference decreases with time. Examination with T l-201 and BMIPP may provide information about the severity of myocarditis.