Which molecule is the oxygen-carrying protein in muscle tissue and is the earliest but non-specific cardiac marker?

Which molecule is the oxygen-carrying protein in muscle tissue and is the earliest but non-specific cardiac marker?

• A. Troponin I
• B. CK-MB
• C. Troponin T
• D. Myoglobin

Answer: (D)

The molecule that carries oxygen in muscle tissue and serves as the earliest but non-specific cardiac marker is myoglobin. Myoglobin is a small heme protein stored in both skeletal and cardiac muscle, delivering oxygen to support muscle metabolism. After heart muscle injury, myoglobin is released into the bloodstream very quickly, often within 1–3 hours, which makes it the earliest detectable marker. However, because it is present in skeletal muscle as well, elevated myoglobin isn’t specific to cardiac injury. In contrast, troponin I and troponin T are highly specific to cardiac muscle but rise a bit later, and CK-MB, while cardiac-associated, can be influenced by skeletal muscle damage and isn’t as early as myoglobin.

The molecule that carries oxygen in muscle tissue and serves as the earliest but non-specific cardiac marker is myoglobin. Myoglobin is a small heme protein stored in both skeletal and cardiac muscle, delivering oxygen to support muscle metabolism. After heart muscle injury, myoglobin is released into the bloodstream very quickly, often within 1–3 hours, which makes it the earliest detectable marker. However, because it is present in skeletal muscle as well, elevated myoglobin isn’t specific to cardiac injury. In contrast, troponin I and troponin T are highly specific to cardiac muscle but rise a bit later, and CK-MB, while cardiac-associated, can be influenced by skeletal muscle damage and isn’t as early as myoglobin.