Age-related changes in the concentration of plasma cholesterol and triglycerides in two groups of rats with inherited widely different levels of spontaneous physical activity.

The plasma concentration of cholesterol and triglycerides was determined in two groups of rats with inherited widely different levels of spontaneous physical activity. Active as well as passive rats of each sex were divided into two subgroups, one with free access to wheel running activity (exercising group), and another for which admittance to the drum was closed (nonexercising group). Plasma concentrations of cholesterol and triglycerides were followed from the age of 3-8 months in females and 3 months to 1 year in males. A pronounced increase with age in the plasma concentration of these lipids was observed in the active male rats. In the passive male rats and in all females, there were no major changes in plasma levels of cholesterol and triglycerides. Corresponding groups of exercising and nonexercising rats had similar plasma levels of these components. The data for male rats show a positive association between the inherited tendency to perform spontaneously a high level of physical activity and an age-related increase in plasma lipids. However, running activity per se does not seem to have any influence on the level of plasma cholesterol and triglycerides in these rats.