And if the cardiac muscle cell is damaged, it will begin releasing its internal components, and that includes releasing the H four LDH molecule. Now, as the cardiac muscle is damaged, releasing the H four LDH into the blood will increase the relative concentration of this molecule inside of the blood. And this molecule is typically not found in a specific high concentration inside our blood. So physicians can basically test for the presence of elevated H four concentration in the blood. And this can basically help them show or help them discover the fact that this individual has experienced a myocardial infraction or a heart attack. So we see that not only can our body control and regulate enzyme activity by using these three different types of mechanisms, it can also use is and isozymes.