In animal cell culture, which laboratory measurement is commonly used to quantify mechanical damage to cells by detecting cytosolic enzyme release into the medium?

Introduction:
During mixing and aeration, animal cells can be damaged by shear and bubble interfaces, leading to loss of membrane integrity. When membranes are compromised, intracellular enzymes leak into the culture medium. Monitoring a reliable cytosolic marker provides a rapid, quantitative assessment of cell damage in process development and scale-up trials.

Given Data / Assumptions:

• We need a sensitive assay that correlates with membrane disruption.
• The assay should be compatible with standard spectrophotometric methods.
• Marker enzyme should be abundant in the cytosol of animal cells.

Concept / Approach:
Lactate dehydrogenase (LDH) is a cytosolic enzyme that rapidly appears in the extracellular medium when cell membranes are damaged. Measuring LDH activity in the supernatant using NADH-linked reactions offers a convenient indicator of mechanical injury. In contrast, bulk metabolites like lactate reflect metabolism rather than direct lysis, and unrelated enzymes such as lactase or lactate oxidase are not appropriate markers for animal cells.

Step-by-Step Solution:

Verification / Alternative check:
Parallel viability assays (for example, trypan blue exclusion) and microscopic observations corroborate LDH leakage results, establishing a consistent picture of shear-induced damage.

Why Other Options Are Wrong:

• Lactate concentration: Reflects metabolic state, not membrane rupture directly.
• Lactate oxidase activity: Not a standard animal cell leakage marker.
• Lactase activity: Enzyme not typically relevant in animal cell cytosol.

Common Pitfalls:
Interpreting LDH without accounting for spontaneous release during normal turnover; include controls. Hemolysis of feeder erythrocytes or serum interference can confound readings; standardize sampling.

Final Answer:
Activity of lactate dehydrogenase in the medium