Advertisement
 

doctorslounge.com

 
Powered by
Careerbuilder

 

                    Home  |  Forums  |  Humor  |  Advertising  |  Contact
   Ask a Doctor

   News via RSS

   Newsletter

   Rheumatology

   News

 

 Conferences


   CME

   Forum Archives

   Diseases

   Symptoms

   Labs

   Procedures

   Drugs

   Links
   Specialties

   Cardiology

   Dermatology

   Endocrinology

   Fertility

   Gastroenterology

   Gynecology

   Hematology

   Infections

   Nephrology

   Neurology

   Oncology

   Orthopedics

   Pediatrics

   Pharmacy

   Primary Care

   Psychiatry

   Pulmonology

   Rheumatology

   Surgery

   Urology

   Other Sections

   Membership

   Research Tools

   Medical Tutorials

   Medical Software

 

 

 

 Headlines:

 
 

Lactate dehydrogenase

Lactate dehydrogenase (LDH) is a ubiquitous enzyme present in both plants and animals. It catalyses the reaction between pyruvate and lactate and vice versa, dependent on the abundance of either. As it can also dehydrogenate hydroxybutyrate, it is occasionally called Hydroxybutyrate Dehydrogenase (HBD). LDH requires NAD+ (Nicotinamide adenine dinucleotide) as a hydrogen acceptor.

Catalytic function of LDH

Enzyme isoforms

Every enzyme is a tetramer of four subunits, where subunits are either H and M (based on their electrophoretic properties.) There are, therefore, five LDH isotypes:

  • LDH-1 (4H) - in the heart
  • LDH-2 (3H1M) - in the reticuloendothelial system
  • LDH-3 (2H2M) - in the lungs
  • LDH-4 (1H3M) - in the kidneys
  • LDH-5 (4M) - in the liver and striated muscle

Usually LDH-2 is the predominant form in the serum: if an LDH-1 level is higher than the LDH-2 level (a "flipped pattern"), myocardial infarction is suggested. This method has been largely superseded by the use of Troponin I or T measurement.

advertisement.gif (61x7 -- 0 bytes)
 

Are you a doctor or a nurse?

Do you want to join the Doctors Lounge online medical community?

Participate in editorial activities (publish, peer review, edit) and give a helping hand to the largest online community of patients.

Click on the link below to see the requirements:

Doctors Lounge Membership Application


Hemolysis

In medicine, LDH is often used as a marker of tissue breakdown. As LDH is abundant in red blood cells, it can function as a marker for hemolysis. A blood sample that has been handled incorrectly can show false-positively high levels of LDH due to erythrocyte damage.

Tissue turnover

Other uses are assessment of tissue breakdown in general; this is possible when there are no other indicators of hemolysis. It is used to follow-up cancer patients, as cancer cells have a high rate of turnover, with destroyed cells leading to an elevated LDH activity.

Exudates and transudates

Measuring LDH in pleural effusion (or pericardial fluid) can help in the distinction between exudates (actively secreted fluid, e.g. due to inflammation) or transudates (passively secreted fluid, due to a high hydrostatic pressure or a low oncotic pressure). LDH is elevated (>200 U/l) in an exsudate and low in a transudate. In empyema, the LDH levels generally exceed 1000 U/l.

Meningitis and encephalitis

The enzyme is also found in cerebrospinal fluid where high levels of lactate dehydrogenase in cerebrospinal fluid are often associated with bacterial meningitis. High levels of the enzyme can also be found in cases of viral meningitis, generally indicating the presence of encephalitis and poor prognosis.

previous.gif (72x17 -- 347 bytes) next.gif (72x17 -- 277 bytes)
 

 advertisement.gif (61x7 -- 0 bytes)

 

 



We subscribe to the HONcode principles of the HON Foundation. Click to verify.
We subscribe to the HONcode principles. Verify here

Privacy Statement | Terms & Conditions | Editorial Board | About us
Copyright 2001-2012 DoctorsLounge. All rights reserved.