MR imaging was performed to investigate whether Gd-DTPA-BMA-induced contrast enhancement of myocardial infarction is counteracted by Dy-DTPA-BMA. Myocardial infarction was induced in 5 pigs. Microdialysate probes were inserted in ischemic and nonischemic myocardium. Gd-DTPA-BMA (0.3 mmol/kg b.w.) and Dy-DTPA-BMA (1.0 mmol/kg b.w.) were administered i.v. 4 hours post occlusion. The microdialysate was collected every 10 min and measured for Gd and Dy using inductively coupled plasma atomic emission spectrometry. The pigs were sacrificed 2 hours after administration of contrast media. The concentration of both contrast agents was 3 times higher in infarcted myocardium than in nonischemic myocardium. The infarctions displayed high signal intensity in spin-echo sequences ex vivo. This lack of detectable susceptibility effects from Dy may be caused by loss of cell membrane integrity in infarcted tissue as shown by our microdialysate and biopsy data.