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Protective action of beta‐carotene against lethal photosensitization of fibroblasts in vitro *
Author(s) -
FRITSCH P.,
GSCHNAIT F.,
HÖNIGSMANN H.,
WOLFF K.
Publication year - 1976
Publication title -
british journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.304
H-Index - 179
eISSN - 1365-2133
pISSN - 0007-0963
DOI - 10.1111/j.1365-2133.1976.tb04382.x
Subject(s) - trypsinization , chemistry , in vitro , cytoplasm , intracellular , cell culture , microbiology and biotechnology , incubation , fibroblast , biochemistry , biology , trypsin , genetics , enzyme
SUMMARY Cell culture experiments using haematoporphyrin photosensitized bovine hoof fibroblasts and longwave uv‐irradiation revealed two distinct and separable patterns of lethal photosensitization according to two different sensitization procedures:1 Photosensitization of cell membranes by short exposure (5 min) of cells to haematoporphyrin. 2 Cytoplasmic photosensitization elicited by a 2 h exposure of cells to hacmatoporphyrin. Cellmembrane photosensitization was reversible by incubation of cells in serum which removed surface bound haematoporphyrin; cytoplasmic photosensitization was irreversible. Beta‐carotene was tested in these two systems and the following results were obtained: ( i ) Preincubation of bovine hoof fibroblasts in β‐carotene protects from lethal haematoporphyrin photosensitization. (2) Protection with β‐carotene is achieved against both types of photosensitization. (3) The protective effect of β‐carotene depends upon the duration of pretreatment, reaching a maximum after 7 days. (4) β‐carotene protection is maintained even after trypsinization of bovine hoof fibroblasts and withdrawal of β‐carotene from the medium for 24 h or more. (5) Haematoporphyrin sensitized bovine hoof fibroblasts show a distinct pattern of red fluorescence for each type of photosensitization. Incubation of bovine hoof fibroblasts in β‐carotene prior to haematoporphyrin photosensitization results in a pronounced reduction of red fluorescence. Some of these data indicate that β‐carotene acts, at least in cell membrane photosensitization, at the level of the cell membrane into which it appears to be incorporated.