Cardiac sarcolemma: compositional adaptation to exercise.

Marked changes were observed in the lipid composition of highly purified plasma membranes isolated from the hearts of rats subjected to daily treadmill running. Compared to sedentary controls, sarcolemmal content of total phospholipid and phosphatidylserine in the trained group was increased 23 and 50 percent, respectively. This observation suggests a mechanism by which cardiac contractility may be enhanced by exercise.