Effect of age and myocardial infarction on serum and heart lactic dehydrogenase.

The effect of isoproterenol (ISO) on the activity of lactic dehydrogenase (LDH) in the serum and heart was investigated in rats belonging to four different age groups. Serum LDH activity increased in all the ages as a result of ISO injection, however, the magnitude and response varied with age. Younger animals were able to recover from the toxicity of ISO much quicker compared to the older ones. An elevation in the LDH enzyme activity in the serum correlated with a decrease in the activity of cardiac muscle LDH in all the age groups of isoproterenol-treated rats.