LDH Release Assay
Quick Facts
| Feature | Information |
|---|---|
| Category | Cytotoxicity / Cell Death Assay |
| Principle | Quantification of extracellular lactate dehydrogenase (LDH) |
| Detection Method | Colorimetric, Fluorometric, or Luminescent |
| Sample Type | Cell culture supernatant |
| Quantitative | Yes |
| Typical Assay Time | 30-60 minutes |
| Typical Output | LDH activity proportional to membrane damage |
| Readout | Absorbance, Fluorescence, or Luminescence |
Overview
The LDH Release Assay is a non-destructive cytotoxicity assay that measures lactate dehydrogenase (LDH) released into the culture medium following damage to the plasma membrane.
LDH is a stable cytoplasmic enzyme present in virtually all mammalian cells. Under normal conditions it remains intracellular, but loss of membrane integrity during necrosis or late-stage apoptosis results in its release into the extracellular environment.
Because the assay analyzes culture supernatant without lysing the remaining cells, it is commonly used to assess drug-induced cytotoxicity, biomaterial compatibility, and immune cell-mediated killing.
Biological Principle
Healthy cells retain LDH within the cytoplasm.
When plasma membrane integrity is compromised:
Cell Membrane Damage
↓
LDH Released into Medium
↓
Enzymatic Detection
↓
Signal Proportional to Cytotoxicity
The amount of extracellular LDH reflects the extent of cell membrane damage.
Principle of Detection
Released LDH catalyzes the conversion of:
Lactate
↓
Pyruvate
↓
Reduction of NAD⁺ to NADH
The generated NADH drives a secondary enzymatic reaction that produces a measurable colorimetric, fluorescent, or luminescent signal.
Signal intensity is proportional to extracellular LDH activity.
Workflow
Cells
↓
Experimental Treatment
↓
Collect Culture Supernatant
↓
Add LDH Detection Reagent
↓
Incubate
↓
Measure Signal
↓
Calculate Cytotoxicity
What Does It Measure?
| Measurement | Interpretation |
|---|---|
| Low extracellular LDH | Intact plasma membrane |
| High extracellular LDH | Membrane damage and cytotoxicity |
| Increasing LDH over time | Progressive cell injury |
| Maximum LDH release | Complete cell lysis (positive control) |
Applications
The LDH Release Assay is commonly used for:
- Drug cytotoxicity testing
- Nanoparticle toxicity studies
- Biomaterial biocompatibility
- Immune cell cytotoxicity assays
- Cancer therapy evaluation
- Infection studies
- Chemical toxicity screening
- High-throughput drug screening
Interpretation of Results
| Observation | Biological Interpretation |
|---|---|
| Low LDH release | Healthy cells with intact membranes |
| Moderate LDH release | Partial cytotoxicity |
| High LDH release | Extensive membrane damage |
| Near-maximal LDH release | Complete cell lysis |
Advantages
- Direct measure of membrane integrity
- Non-destructive to remaining cells
- Suitable for adherent and suspension cultures
- Compatible with multiwell plate formats
- High-throughput screening compatible
- Can be combined with viability assays for complementary analysis
Limitations
- Detects membrane damage rather than early apoptosis
- Late apoptotic and necrotic cells may produce similar results
- High spontaneous LDH release can reduce assay sensitivity
- Serum and certain compounds may interfere with enzyme activity
- Requires appropriate low and high LDH controls for accurate normalization
Comparison with Similar Assays
| Assay | Primary Measurement |
|---|---|
| LDH Release | Plasma membrane integrity |
| CellTiter-Glo | Intracellular ATP |
| MTT | Cellular metabolic activity |
| Resazurin | Cellular redox activity |
| Annexin V | Early apoptosis |
| Trypan Blue | Membrane permeability by dye exclusion |
Common Misinterpretations
- LDH release does not distinguish necrosis from late apoptosis.
- Low LDH release does not necessarily indicate healthy metabolism.
- High LDH release reflects membrane damage but not the underlying mechanism of cell death.
- Results should be interpreted alongside viability or apoptosis assays for comprehensive analysis.
Key Takeaways
- The LDH Release Assay measures extracellular lactate dehydrogenase released after loss of plasma membrane integrity.
- It is a widely used assay for quantifying cytotoxicity and membrane damage.
- Because only culture supernatant is analyzed, the remaining cells can often be used for additional downstream assays.
- LDH release correlates with the extent of cell injury but cannot independently distinguish different forms of cell death.
- Combining LDH measurements with viability or apoptosis assays provides a more complete assessment of cellular responses.
References
- Korzeniewski C, Callewaert DM. An enzyme-release assay for natural cytotoxicity. Journal of Immunological Methods (1983).
- Riss TL et al. Cell Viability Assays. Assay Guidance Manual.
- Promega. CytoTox 96® Non-Radioactive Cytotoxicity Assay Technical Manual.
- Freshney RI. Culture of Animal Cells: A Manual of Basic Technique and Specialized Applications.
- ATCC. Cell Viability and Cytotoxicity Assays.