PROLONGED ACTIVATION OF THE BRANCHED-CHAIN ALPHA-KETO ACID DEHYDROGENASE COMPLEX IN MUSCLE OF ZYMOSAN TREATED RATS

Whole-body oxidation rates of branched chain amino acids (BCAA) are in creased during catabolic diseases. A significant role for muscle in th is feature has been suggested and, therefore, activities of the rate l imiting enzyme in the degradative pathway of the BCAA in muscle were i nvestigated in a catabolic rat model (intraperitoneal zymosan injectio n). Both actual and total activities of the branched chain cr-keto aci d dehydrogenase complex (BC-complex) were measured in skeletal muscle of zymosan treated rats and compared with values measured in pair fed and ad libitum fed controls. The actual activity and the percentage of the enzyme in the active form were increased 2 and 6 days after the z ymosan challenge. Total activity of the BC-complex and the activities of mitochondrial marker enzymes were reduced 2 days after zymosan trea tment. We conclude that zymosan treatment leads to (1) a reduction of the mitochondrial content in skeletal muscle and (2) a prolonged activ ation of the BC-complex in muscle which may explain enhanced oxidation of BCAA during catabolic diseases.