Extracellular release of enzymes from macrophages in vitro for measuring cellular interaction with particulate and non-particulate materials

Abstract

Mammalian cells in culture provide a sensitive and rapid in vitro test for the study of many aspects of toxicity impractical in vivo. Assays have been established for eight enzymes used as markers for different sub-cellular locations (plasma membrane, cytoplasm, mitochondria and lysosomes). The time-course and dose-response relationships of enzyme release from macrophages exposed to a series of toxic and non-toxic mineral dusts and soluble detergents have been examined. The different patterns of extracellular enzyme release illustrate the basic mechanisms of cell damage, covering non-toxic interactions (little or no enzyme release except at very high concentrations), immediate cytotoxicity (lysosomal and cytoplasmic enzyme release at similar rates, with the majority of enzyme release occurring within the first 4 hr), delayed cytotoxicity (lysosomal and cytoplasmic enzyme release at similar rates increasing exponentially over 17 hr), phagocytic release/activation (selective release of lysosomal enzymes in the absence of cytoplasmic enzymes) and membranolytic interaction (selective release of cytoplasmic enzymes with relatively little lysosomal enzyme release). Enzyme release from macrophages in vitro can provide information about the site and nature of cytotoxic interactions.