Amino Acids, Proteins and Porphyrins
Serum total lactate dehydrogenase level which NOT be raised in:
|A||Muscle crush injury.|
a. Normal value of LDH in serum is 100-200 U/L.
LDH level is 100 times more inside the RBC than in plasma, and therefore minor amount of hemolysis with result in a false-positive test
b. LDII (Total) increased: - in — MI, Hemolytic Anemia, Hepatocellular damage, muscular dystrophy,
carcinomas leukemia, and any condition which causes necrosis of the body.
c. Isoenzymes of the LDH — Since total LDH is increased in many conditions, the study of isoenzymes of LDH is of great importance.
Eg.ofIsoenzymes of LDH (and sources):-
i. LDH1→H4 (Heart muscle) [Q All India 2005]
ii. LDH2→H3M1 (RBC)
iii. LDH3→H2M2 (Brain)
iv. LDH4→H1M3 (Liver)
v. LDH5→M4 (Skeletal muscle)
4. In MI - Normally LDH2 conc. in blood > LDH1, but this pattern is reversed in M.I. → this called FLIPPED PATTERN. In M.I., LDH starts to rise after 12 hours, reaches peak after 2 to 3 days and may remain elevated for a week or more.
5. Important point
a. LDH-1 (H4)→Predominates in Heart tissues, fastest moving (most —ye) on electrophoresis and heat stable.
b. LDH-5 (M4) →predominates in Liver, slowest moving on electrophoresis and is inhibited by Urea [Heat stability and inhibition by urea are used to differentiate these two isoenzyme i.e.LDH1 and LDH5]