| Autor: |
Tsuda, Hirohisa, Yoshida, Daisuke, Mizusaki, Shigenobu |
| Zdroj: |
Carcinogenesis; 1984, Vol. 5 Issue 3, p331-334, 4p |
| Abstrakt: |
The cytotoxic effect of 4-nitroquinoline-1-oxide (4NQO) on cultured Chinese hamster cells was drastically reduced by the presence of caffeine (0.2 − 1 mM). Caffeine, however, did not reduce the cytotoxicity of 4-hydroxyaminoquinoline-1-oxide (4HAQO), an active metabolite of 4NQO. The 105 000 supernatant from the cell homogenate could catalyze the conversion of 4NQO to 4HAQO in the presence of NADPH or NADH as a hydrogen donor. This enzyme activity was strongly inhibited by caffeine (0.1 − 10 mM) or dicumarol (10 − 10 M), an inhibitor of DT diaphorase (E.C.1.6.99.2). Dicumarol also reduced the cytotoxicity of 4NQO. These results clearly suggest that caffeine inhibits the conversion step of 4NQO to 4HAQO, resulting in a decrease in the cytotoxicity of 4NQO. Furthermore, the frequency of 6-thioguanine-resistant mutation by 4NQO was also strongly reduced by the presence of caffeine (1 mM) in cultured Chinese hamster cells, being consistent with the results of cytotoxicity. [ABSTRACT FROM PUBLISHER] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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