Damage to RBC resulting in their lysis, increases which isoenzyme in blood?
**Core Concept**
The question relates to the breakdown of red blood cells (RBCs), leading to the release of intracellular enzymes into the bloodstream. This process is known as hemolysis. The isoenzymes in question are lactate dehydrogenase (LDH) isoenzymes, specifically LDH-2, which is predominantly found in RBCs.
**Why the Correct Answer is Right**
During hemolysis, the RBC membrane is damaged, allowing the contents of the RBC to leak into the bloodstream. LDH-2 is one of the isoenzymes that is predominantly found in RBCs. When RBCs are lysed, LDH-2 is released into the bloodstream, leading to an increase in its concentration. LDH-2 is a cytosolic enzyme that catalyzes the interconversion of lactate and pyruvate. Its high concentration in RBCs makes it a useful marker for diagnosing hemolysis.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because LDH-1 is the isoenzyme predominantly found in the heart, not RBCs.
* **Option B:** This option is incorrect because LDH-3 is the isoenzyme predominantly found in the lungs, not RBCs.
* **Option D:** This option is incorrect because LDH-5 is the isoenzyme predominantly found in the liver and skeletal muscle, not RBCs.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that LDH-2 is a specific marker for hemolysis, and its elevation can be seen in conditions such as hemolytic anemia, sickle cell disease, and intravascular hemolysis.
**Correct Answer:** C.