What causes an increase in serum creatine kinase MB (CKMB) levels after myocardial ischemia?

An increase in serum creatine kinase MB (CKMB) levels after myocardial ischemia is primarily due to increased plasma membrane permeability. Myocardial ischemia leads to a shortage of oxygen and nutrients in the heart muscle, causing damage to the myocardial cells. When these cells become damaged, the integrity of their plasma membranes is compromised, allowing intracellular enzymes like CKMB to leak into the bloodstream.

CKMB is an isoenzyme of creatine kinase that is predominantly found in cardiac muscle. When myocardial cells are injured, the elevated levels of CKMB in the serum can serve as a marker for myocardial damage. The higher the degree of ischemia and the resultant cell injury, the greater the increase in serum CKMB levels.

In contrast, while cellular repair processes and increased mitochondrial function may occur after an ischemic event, these processes do not directly account for the immediate increase in serum CKMB levels. Similarly, an increase in Golgi activity is not a primary factor influencing CKMB release during acute myocardial damage. The key mechanism of interest in this situation is the disruption of the plasma membrane, leading to the release of cellular contents, including CKMB, into the circulation.