Purine Degradation in Contracting Fast and Slow Muscles of Rats
We previously reported that hyperuricemia found in patients with glycogenosis types III, V, and VII was caused by excess purine degradation due to impaired ATP generation in muscles (myogenic hyperuricemia)(Kono et al., 1986, 1987; Mineo et al., 1987). Even minimal or mild exercise leads to elevated levels of blood inosine and hypoxanthine in patients with metabolic myopathy (Bertorini et al., 1985; Brooke et al., 1983; Hara et al., 1987; Kono et al., 1986; Mineo et al., 1985). Inosine and hypoxanthine serve as precursors of uric acid in the liver. When ATP is utilized during strenuous contraction of skeletal muscle, AMP is deaminated to IMP by AMP deaminase (EC. 220.127.116.11). AMP and IMP are broken down into adenosine and inosine, respectively, by 5′-nucleotidase (EC. 18.104.22.168). It has been reported that regulation of adenine nucleotide degradation is different between fast and slow muscles. Bookman et al. (1983) reported that nucleosides increased in proportion to an increase in lactate in cat slow muscles but not in fast muscles. Meyer et al. (1979) reported that large amount of IMP was produced in fast muscles but there was no significant increase in IMP in slow muscles during ischemic contraction, while Whitlock et al. (1987) showed adenine nucleotide deamination to IMP could occur in slow muscles under specific contraction conditions. However, difference in purine degradation between fast and slow muscles is still controversial. This study was designed to clarify overall purine degradation and its regulation in different types of rat skeletal muscles during ischemic contraction.
KeywordsSoleus Muscle Extensor Digitorum Longus Glycogen Storage Disease Extensor Digitorum Longus Muscle Slow Muscle
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