Abstract: Purpose: The objective ofthis project is to evaluate biodistribution of ¹³¹IIodosennoside Ain normal mice and explore the feasibility on the diagnosis of myocardialinfarction. Methods: Iodogen method was used to radioiodinate sennoside A with ¹³¹I.¹³¹IIodosennoside A was intravenously injected into mice. Threegroups of mice were killed at 4 h, 24 h and 48 h post injection respectivelyand the radioactive uptake in major organs were calculated. Rats were subjectedto left anterior descending (LAD) coronary artery ligation to induce acutemyocardial infarction. Rat models of myocardial infarction were intravenouslyinjected ¹³¹Iiodosennoside A. 24 h after injection of ¹³¹IiodosennosideA, the regional distribution of radioiodinated sennoside A was determined byradioactivity counting technique. 2,3,5-triphenyl tetrazolium chloride (TTC)staining and autoradiography were performed with 2 mm thick sections of heartsfor postmortem verifications. Results: The study showed high uptake of ¹³¹IiodosennosideA in kidneys and fast blood clearance. At 24 h post injection, radioactivityconcentration in infarcted myocardium was over 11.9 times higher than in normalmyocardium. Preferential uptake of the ¹³¹Iiodosennoside A innecrotic tissue was confirmed by perfect match of images from TTC staining andautoradiography. Conclusion: The result proved that ¹³¹IiodosennosideA has myocardial necrosis affinity and may serve as a marker on the diagnosisof myocardial infarction.