Lung Surfactant Bioassay

The Lung Surfactant (LS) Bioassay is a cell-free method designed to assess acute lung toxicity shortly after inhalation, focusing on immediate alveolar effects. It evaluates LS function, which is crucial for healthy lungs, by monitoring surface tension and rheological changes in a 'breathing' drop of pig-derived LS exposed to test compounds. Increased surface tension, as measured with a Constrained Drop Surfactometer, and altered surface rheology, as calculated with a mathematical model, are considered inhibitory to LS function, potentially leading to alveolar collapse and breathing difficulties. Inhibition of LS function is identified as the Molecular Initiating Event in Adverse Outcome Pathway 302, predicting acute lung effects.

According to the test submitter, the LS Bioassay is intended for non-regulatory prioritisation and chemical screening in research and development. While it assesses one of many inhalation effects, it might complement other lung-relevant in vitro methods and potentially replace acute inhalation toxicity tests following OECD Test Guidelines (TGs) that rely on systemic effects. Immediate lung effects can be noted in these TG studies by observing respiration changes. Coupling this method with OECD TGs can offer insights into the mechanism of toxicity of test compounds.