FIBER-TYPE COMPOSITION AND ENZYME-ACTIVITIES OF MUSCLES IN 2 MODELS OF OBESE RATS

1. In oxidative (soleus) and glycolytic (extensor digitorum longus) mu scles of obese Zucker rats, a significant decrease in the percentage o f relative area occupied by glycolytic fibers was observed. 2. The act ivity of citrate synthase and beta-hydroxy-acyl-CoA-dehydrogenase was significantly higher in muscles of obese than of lean Zucker rats. 3. In rats, 6 weeks after lesion of the ventromedial hypothalamus, no cha nges were observed. 4. This indicates that neither the proportion of o xidative fibers, nor the oxidative capacities are decreased in skeleta l muscles of obese rats suggesting that insulin resistance cannot be a scribed to a higher glycolytic-oxidative fiber ratio.