Gallium-67 citrate (67Ga) accumulation and various enzyme activities during the repair of rat heart with infarct-like lesions induced by isoproterenol (ISP) treatment were measured for 10 days after treatment. Serum creatine phosphokinase (CPK) and glutamic oxalacetic transaminase (GOT) activities were increased immediately after ISP treatment, reaching maximum levels of activity of 545 +/- 64 U/ml and 542 +/- 94 KU/ml, respectively, within 12 h. Uptake of 67Ga in the rat heart was elevated 12 h after ISP treatment, reaching a maximum on day 1 (0.473 +/- 0.015% dose/g heart). This pattern was essentially similar to the pattern of uronic acid content in the 1.2 M NaCl fraction, which contained mainly heparan sulfate (HS). The activity of glucose-6-phosphate dehydrogenase (G-6-PDH), a marker enzyme for fibrogenesis of damaged tissues, was also elevated 12 h after the ISP treatment, reaching a maximum of approximately 2.47 times that of the control heart on day 1. On the other hand, there were no significant changes in the 67Ga uptake and uronic acid content in any of the fractions of the liver and kidneys. These findings suggested that HS might be an acceptor for 67Ga accumulation during the repair of rat heart with infarct-like lesions, in accord with our previous results on CCl4-damaged rat liver.