CONTRIBUTION OF HYPOXIA TO THE DEVELOPMENT OF CARDIOMYOPATHY IN HAMSTERS

Objective: It has been hypothesized that microvascular spasms cause ca rdiomyopathy. To elucidate the contribution of hypoxia to the developm ent of cardiomyopathy, the newly-developed hypoxia tracer, Tc-99m nitr oimidazole, was applied to detect myocardial hypoxia in a hamster mode l. Methods: Tc-99m nitroimidazole (180 MBq) and I-125 iodoantipyrine ( 370 kBq) were injected into cardiomyopathic Syrian hamsters or control hamsters at age 10, 25, and 40 weeks (n = 6 in each group). The myoca rdial uptake of Tc-99m nitroimidazole was measured and dual tracer aut oradiography was performed. Results: Histologic study revealed that th e cardiomyopathic hamsters at age 10, 25 and 40 weeks were in the myoc ytolytic stage, the fibrotic and healing stage, and the hypertrophy an d dilatation stage, respectively. Tc-99m nitroimidazole uptake was sig nificantly greater in the cardiomyopathic hamsters than in the control s at age 25 weeks (cardiomyopathic hamsters, 33.3 +/- 4.7% g dose/g; c ontrol, 25.2 +/- 3.1), whereas there were no significant differences b etween both strains at age IO and 40 weeks. The quantified concentrati on of I-125 iodoantipyrine in the cardiomyopathic hamster at age 40 we eks was significantly lower than that in the controls. When the Tc-99m nitroimidazole uptake was normalized by I-125 iodoantipyrine concentr ations, the cardiomyopathic hamsters at age 25 and 40 weeks showed sig nificantly greater uptake than the controls. Conclusion: The myocardiu m in cardiomyopathic hamsters was hypoxic at the fibrotic and healing stage and may be hypoxic at the hypertrophy and dilatation stage. This may contribute to the development of cardiomyopathy. (C) 1997 Elsevie r Science B.V.