Enzyme activities of energy metabolism in muscle and brown fat of germ-free rats

Abstract

The heart is smaller in germ-free (GF) rats and the resting oxygen consumption is 20—30 0/0 lower than that in their microbially-associated (MA) counterparts. In this study organ weights and enzyme activities of energy metabolism were measured from myocardial and skeletal muscles and interscapular brown adipose tissue (BAT) of GF and MA rats. GF and MA rats had similar body weights. Caecum was 4—6 times heavier in GF than in MA rats. Especially in females the heart,
liver and BAT were lighter, and kidneys heavier in GP than in MA rats. The adrenals of GF males were heavier than in MA males. There were no differences between GF and MA females in glycogen content and activities of Citrate synthase, lactate
dehydrogenase, malate dehydrogenase and phosphofructokinase from myocardial and skeletal muscles. BAT was lighter in GF than in MA females and it contained less fat. The activities of citrate synthase and malate dehydrogenase were higher in the BAT of CF females and the same tendency was seen in the males. The results suggest that the decreased oxygen consumption in GF rats is likely to be due to factors other than muscular energy metabolism.