Suppressive effects of urine on the SOS responses induced by UV and chemical mutagens.
We studied the antimutagenic effects of urine on the SOS-inducing activity of mutagenic substances by using a novel test system (umu-test) for detecting DNA damaging agents, which uses a new tester strain (Salmonella typhimurium TA1535/pSK1002). The SOS-inducing activity of chemicals was detected in terms of the level of umu operon expression by measuring beta-galactosidase activity. We first examined the effects of various amounts of urine on SOS responses caused by mitomycin C (MMC). As a result, the urine suppressed beta-galactosidase activity of MMC dose-dependently. A urine concentration of 50 microliters/ml in the medium also suppressed 89.9% of SOS response induced by 0.1 microgram/ml of PEP, 75.6% of that induced by 0.02 microgram/ml of AF2 and 60.9% of that induced by 0.1 microgram/ml of AFB1. In addition, a urine concentration of 50 microliters/ml in the medium also suppressed 85.6% of SOS response by 5 J/m2 of UV irradiation. The observed suppression seemed to be directly related to the SOS responses at a cellular level, rather than to interaction between urine and mutagens, because the urine suppressed SOS responses induced not only by various mutagens but also by UV irradiation. These results suggest that urine works as a strong antimutagen against UV and chemical substances.
Department of Urology, Osaka City University Medical School, Japan.
S
S
Ikemoto
M
M
Kamizuru
N
N
Hayahara
S
S
Wada
T
T
Kishimoto
D016587:Antimutagenic Agents / Q000032:analysis / Q000494:pharmacology*; D006801:Humans; D008937:Mitomycins / Q000037:antagonists & inhibitors; D013014:SOS Response, Genetics; D014466:Ultraviolet Rays; D014556:Urine / Q000737:chemistry / Q000502:physiology*; D001616:beta-Galactosidase / Q000378:metabolism
D016587:Antimutagenic Agents; D008937:Mitomycins; C046000:mitomycin A; D001616:beta-Galactosidase