The influence of 5-fluorouracil on the a-ketoglutarate dehydrogenase complex in rat's cardiac muscle -- a preliminary study.

5-fluorouracil (5-FU), which is a commonly used chemotherapy agent exerts undesired cardiac toxicity. Mitochondrial dysfunction is thought to be one of potentially important mechanisms of 5-FUinduced cardiotoxicity. a-ketoglutarate dehydrogenase (a-KGDHC) is the key regulatory enzyme of TCA cycle. The complex consists of multiple copies of three catalytic subunits: a-ketoglutarate dehydrogenase (E1), dihydrolipoamide succinyltransferase (E2) and dihydrolipoamide dehydrogenase (E3). a-KGDHC together with branched chain a-ketoacid dehydrogenase (BCKDHC) and pyruvate dehydrogenase (PDHC), are the members of 2-oxoacid dehydrogenases family that share some structural and functional similarities. Recently, it has been found that 5-FU stimulates BCKDHC in rat's cardiac muscle. Therefore, we hypothesize that 5-FU modifies a-KGDHC activity and affects cardiac muscle metabolism. The aim of this study was to determine the effect of 5-FU on a-KGDHC activity and protein levels of E1 and E2 subunits of the complex in rat's cardiac muscle. Wistar male rats were administered with 4 doses of 5-FU, 150 mg/kg b. wt. each (study group) or 0.3% methylcellulose (control group). a-KGDHC activity was assayed spectrophotometrically. The E1 and E2 proteins levels were quantified by Western blot. 5-FU administration resulted in stimulation of myocardial a-KGDHC activity in rats. In addition, E2 protein level increased in response to 5-FU treatment, while the E1 protein level remained unchanged. Upregulation of a-KGDHC appears to result from change in E2 subunit protein level. However, the effect of 5-FU on factors modifying a-KGDHC activity at post-translational level cannot be excluded. [ABSTRACT FROM AUTHOR]