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DIRECT EXPOSURE OF MANNALIAN CELLS TO PURE EXOGENOUS SINGLET OXYGEN (Δ g O 2
Author(s) -
Dahl Thomas A.
Publication year - 1993
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1993.tb02283.x
Subject(s) - singlet oxygen , biophysics , cell , fibroblast , chemistry , oxygen , cell culture , cell damage , in vitro , biology , biochemistry , genetics , organic chemistry
Mammalian cells attached to membrane filters or deposited on filters without attachment were exposed to gas‐phase singlet oxygen ( 1 O 2 ) in the absence of any other reactants. Cells were exposed in a monolayer or less, in the absence of external medium, during steady‐state 1 O 2 generation, ensuring that singlet oxygen impinged directly and equally on all cells simultaneously. The current methodology for cell exposure ensures that 1 O 2 is initially the only reactive species to which the cells are exposed. Results seen with this system can therefore be attributed solely and unambiguously to events initiated by 1 O 2 . Further, all cells in the sample receive the same magnitude of exposure per surface area per time interval, which supports calculations of the amount of 1 O 2 required for irreversible cell damage, based on measured 1 O 2 flux and exposed cell surface area. Exposure to pure 1 O 2 irreversibly damaged a variety of cell types, including rat basophilic leukemia, human squamous carcinoma and Chinese hamster lung fibroblast cell lines, and murine primary hepatocytes. Cell survival curves following exposure to 1 O 2 followed apparent first‐order kinetics. A large number of singlet oxygen collisions (˜ 10 12 ‐10 13 ) were required to inactivate a cell, on average, indicating a low probability that singlet oxygen collision will reduce cell survival. Regardless of cell type or the survival endpoint measured, lethal toxicity required a fairly constant number of 1 O 2 collisions per cell. This poses a serious caveat in the assignment of causality in correlating 1 O 2 ‐initiated cellular damage with mechanism of death, i.e. most damage observed will not be related to death. The importance of various toxic effects of 1 O 2 , whether lethal or nonlethal, will depend on the magnitude of exposure and therefore on the context in which exposure occurs.