Molecular biologic Changes of Adenine Nucleotide Translocator in J-2-N Cardiomyopathic Hamsters
The adenine nucleotide translocator (ANT) is an integral protein present in the inner mitochondrial membrane that performs the exchange of cytoplasmic and intramitochondrial ADP and ATP. The ANT content of the myocardium was studied in J-2-N cardiomyopathic hamsters. The ANT content was significantly decreased in J-2-N hamsters. By molecular biologic analysis, hamster ANT cDNA of the Tl isoenzyme was cloned by the plaque hybridization method. The ANT cDNA hybridized specifically with ANT mRNA, so RNA dot-blot hybridization was performed. The highest ANT mRNA level was observed in control hamsters followed by J-2-N hamsters with mild myocardial damage, J-2-N hamsters with severe myocardial damage, and Bio 14.6 cardiomyopathic hamsters. These results suggest that a decreased ANT content may contribute to the pathogenesis of cardiomyopathy and that a decrease in ANT mRNA levels may explain the abnormalities of ANT in J-2-N cardiomyopathic hamsters.
The adenosine nucleotide translocator (ANT) is found in the mitochondrial inner membrane [1-4]. ANT transports ATP to the cytoplasmic side and countertransports ADP into the mitochondrial matrix [5,6]. ANT plays an important role in cardiac mitochondrial energy supply. In our previous study on impaired cardiac contractility , the changes in myosin isoenzymes  have been shown using J-2-N cardiomyopathic hamsters. ANT antibodies have been found by Schulze et al.  in a dilated cardiomyopathic patient. It has been suggested that these abnormalities appear to be involved in the etiology of idiopathic cardiomyopathy .
In the present study we investigated the relationship between quantitative abnormalities of the ANT and cardiomyopathy by determining mitochondrial ANT content in the myocardium. Also, we analyzed the molecular abnormalities of ANT using hamsters with idiopathic cardiomyopathy in our laboratory.
In recent years molecular biologic approaches to ANT have been taken . The base and amino acid sequences of ANT have been determined in humans, cows, and other animals [12–15], and isoenzymes of Tl to T3 have been found. The Tl isoenzyme has been reported to be expressed predominantly in cardiac muscle; therefore, in this study we investigated the myocardial level of the ANT Tl isoenzyme in cardiomyopathic hamsters. We used the cardiomyopathic hamster J-2-N strain, bred in our laboratory . J-2-N hamsters 10 weeks of age underwent electrocardiography, including both limb and chest leads, and then laparotomy was performed under pentobarbital anesthesia. The blood of hamsters was collected from the inferior vena cava, and serum was separated for biochemical analysis.
Golden hamsters were used as controls, and J-2-N hamsters were used as the cardiomyopathic animal model. Because the serum creatine kinase (CK) level correlates well with myocardial damage in J-2-N cardiomyopathic hamsters, it was used to classify the severity of myocardial damage.
J-2-N cardiomyopathic hamsters were divided into a very high serum CK group (>10,OOOmU/ml; J-2-N I), a high CK group (3000-10,000 mU/ml; J-2-N II), a moderate CK group (1000-3000 mU/ml; J-2-N III), and a slightly raised CK group (<1000mU/ml; J-2-N IV). A Bio 14.6 cardiomyopathic hamster group was also investigated.
KeywordsCreatine Kinase Myocardial Damage Golden Hamster Northern Blot Hybridization Adenosine Nucleotide Trans
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- 6.Gawaz M, Douglas MG, Klingenberg M. Structure-function studies of adenine nucleotide transport in mitochondria. II Biochemical analysis of distinct AAC1 and AAC2 proteins in yeast. J Biol Chem 265:14202–14208, 1990.Google Scholar
- 7.Takeda N, Yang J, Iwai T, Tamamura A, Takeda A, Kato M, Ohkugo T, Nagano M. Alterations of myocardial contractility in cardiomyopathic J-2-N hamsters. In: The Cardiomyopathic Heart. Nagano M, Takeda N, Dhalla NS (eds). New York: Raven Press, 1994, pp 23–29.Google Scholar
- 16.Kato M, Nagano M. Experimental animal models of cardiomyopathy. In: Cardiomyopathy Update-4. Metabolic and Molecular Aspects of Cardiomyopathy. Opie LH, Sugimoto T (eds). Tokyo: University of Tokyo Press, 1991, pp 69–81.Google Scholar
- 18.Kato M, Yamashina S, Takeda N, Mochizuki S, Morishita T, Nagano M. Molecular biological and quantitative abnormalities of ADP/ATP carrier protein in cardiomyopathic hamsters. Eur Heart J, in press.Google Scholar