A histological section of the left ventricle of a deceased 28-year-old male shows classic contraction band necrosis of the myocardium. Biological specimens confirm the presence of cocaine and metabolites. Activity of which of the following enzymes was most likely increased in the patient’s myocardial cells sholy prior to his death?
**Core Concept**
Contraction band necrosis is a characteristic histopathological finding in myocardial tissue subjected to intense and prolonged contraction, often due to catecholamine excess. This condition is typically seen in patients who have used cocaine, a potent stimulant that increases sympathetic activity and subsequently causes an excessive release of catecholamines.
**Why the Correct Answer is Right**
The increased activity of phosphofructokinase-1 (PFK-1) in the patient's myocardial cells is likely due to the elevated levels of cyclic AMP (cAMP) and subsequent activation of protein kinase A (PKA). PKA phosphorylates and activates PFK-1, leading to an increase in glycolytic flux and ultimately contributing to the development of contraction band necrosis. This is because PFK-1 is a key regulatory enzyme in the glycolytic pathway, and its activation promotes the breakdown of glucose to pyruvate, which is then converted to lactate, producing a significant amount of ATP.
**Why Each Wrong Option is Incorrect**
**Option A:** Phosphoenolpyruvate carboxykinase is a key enzyme in gluconeogenesis, and its increased activity would be more relevant in the context of glycogenolysis or gluconeogenesis, rather than glycolysis.
**Option C:** Pyruvate dehydrogenase is a key enzyme in the conversion of pyruvate to acetyl-CoA, which is then fed into the citric acid cycle. Although it plays a crucial role in energy metabolism, its increased activity is not directly related to the development of contraction band necrosis.
**Option D:** Succinate dehydrogenase is a key enzyme in the citric acid cycle and is also involved in the electron transport chain. Its increased activity would be more relevant in the context of oxidative phosphorylation, rather than glycolysis.
**Clinical Pearl / High-Yield Fact**
Cocaine use can lead to a range of cardiovascular complications, including myocardial infarction, arrhythmias, and cardiac arrest, due to its potent stimulant effects on the sympathetic nervous system. Contraction band necrosis is a characteristic histopathological finding in cocaine-induced myocardial damage.
**✓ Correct Answer: B. Phosphofructokinase-1**