Biochemical responses of the myocardium and red skeletal muscle to Salmonella typhimurium infection in the rat

Summary. Previous studies with bacterial infections have demonstrated a reduced exercise capacity and equally pronounced catabolic responses in red and white skeletal muscle. In the present study, red skeletal muscle and heart ventricular muscle were compared in a S. typhimurium model in rats. Two days before median lethality was achieved, the activities of one oxidative (cytochrome c oxidase), one glycolytic (glyceraldehyde-3-phosphate dehydrogenase) and one lysosomal (beta-glucuronidase) enzyme were determined in the two tissues. The contents of protein, RNA and DNA were also determined. The oxidative and glycolytic capacity decreased 24–29% in red skeletal muscle but only 7–20% in the myocardium. However, the decrease in oxidative capacity in skeletal muscle and myocardium was statistically correlated. The protein synthetic capacity (RNA) also decreased and was correlated to the protein concentration in both tissues. This metabolic impairment of both skeletal and heart muscle probably contributes to the deterioration of the physical performance capacity previously observed to follow acute infectious diseases. This study emphasizes the importance of the choice of reference, such as ‘wet’ weight, DNA or the entire organ, when evaluating metabolic results in biologic tissues and that biochemical alterations in skeletal muscle biopsies in bacterial infections do not reflect alterations in myocardium reliably.