Calmodulin activity in aging rat heart

Calcium has been known to play an important role in the aging process. Intracellular calcium is regulated by a number of calcium binding proteins including calmodulin. In cardiac tissue, calmodulin is known to regulate a variety of functions. Therefore, to identify possible relationships between calmodulin and the aging process, heart tissue was collected from rats aging 3 weeks to 1 year. Heart tissue was homogenized in a homogenizing buffer and processed for soluble and membrane fractions. These fractions were further subjected to heat treatment. The heat-treated extracts rich in heat stable proteins were used for different experiments. The calmodulin activity was determined as a measure of stimulation of activator deficient 3'-5' phosphodiesterase. The activity of calmodulin at different ages was compared, and no significant changes were observed between 3 weeks vs. 8 weeks, 3 weeks vs. 6 months, and 3 weeks vs. 1 year. The soluble fractions also followed a similar trend, but there was a significant difference between 3 weeks vs. 1 year. At this point we do not know whether the decrease in activity is due to lower expression of calmodulin or decreased ability to stimulate the target enzyme. However, these data suggest that calmodulin may have some association with the aging process.