(21) LDH - MI PROFILE Flashcards
- Catalyzes the interconversion of lactic & pyruvic acids
- Widely distributed, highest activities in heart, hepatic, skeletal muscle & RBCs
LDH
LDH Main source for monomers:
Heart & skeletal muscles (H & M are the 2 active subunits)
LDH Coenzyme/2nd substrate:
NADH
o Slowest to elevate among all the MI markers.
o Buttt a good indicator for px’s response to therapy
LDH
After MI, LD begin to rise within____, peak at _____, & remains elevated in serum for _____.
After MI, LD begin to rise within 10-24hrs, peak at 48-72hrs (2-3 days), & remains elevated in serum for 10 days.
Assay of enzyme activity for LD:
▪ Forward rxn (Lactate → Pyruvate); left to right rxn
▪ Oxidized NAD to reduced NADH
▪ ↑in absorbance is monitored @ 340nm
▪ Optimal pH: 8.3-8.9
Wacker method
Assay of enzyme activity for LD:
▪ Reverse rxn (Pyruvate → Lactate); right to left rxn
▪ More rapid than wacker but should be performed STAT
▪ Reduced NADH to oxidized NAD
▪ ↓in absorbance is monitored @ 340 nm
▪ 3x faster but more susceptible to substrate exhaustion
▪ Optimal pH: 7.1-7.4
Wrobleuski La Due
Assay of enzyme activity for LD:
▪ Has greater affinity of H subunits
* The greater the H subunit in LDH isoenzyme, the greater the affinity of a-HBD.
▪ Represent LDH-1
* Bcos LDH-1 is composed only of H subunit
A-hydroxybutyrate dehydrogenase (a-HBD)
LD isoenzymes
o Tetramer w/ 2 active subunits
H & M
Relative concentration in normal serum:
LDH2 → LDH1 → LDH3 → LDH4 →LDH5
In AMI & Intravascular hemolysis, LDH1 & LDH2 demonstrate a flipped pattern (LDH1 > LDH2)
LDH1 → LDH2 → LDH3 → LDH4 →LDH5
LDH-1 (HHHH)
Tissue: Heart, RBC
MI, Hemolytic anemia
LDH-2 (HHHM)
Tissue: Heart, RBC
RI, Megaloblastic anemia
LDH-3 (HHMM)
Tissue: Lung, Spleen, Pancreas
Pulmonary embolism
LDH-4 (HMMM)
Tissue: Liver
Hepatic Injury
