Calcium-Induced Cell Death: Susceptibility of Cardiac Myocytes Is Age-Dependent

Rat hearts perfused with calcium-free media exhibit an age-dependent response when a normal calcium concentration is restored to the perfusate. The response of 15- and 26-day hearts is an explosive cell death which includes immediate cessation of contractile activity, as well as release of large amounts of creatine phosphokinase activity and myoglobin. Between birth and 15 days of age, the sensitivity of the heart to this calcium-induced cellular disruption changes from a relative insensitivity before 6 days of age to a slight but constant sensitivity from 7 to 11 days of age, and to full sensitivity at 15 days of age. This pattern of sensitivity may be due to the rapid increase in complexity and quantity of the membrane systems of cardiac myocytes during the first 15 days of growth.