Naturally occurring plant
phenols, protocatechuic and tannic
acids, have been reported to be inhibitors of chemical mutagenesis and
carcinogenesis in experimental models. Our previous studies, have shown that these compounds modulate the activity of phases 1 and 2
enzymes in rodents. The aim of the present study was to investigate whether these compounds affect
protein levels of rat hepatic and renal
glutathione S-transferase (GST)
isozymes. Male Wistar rats were treated intraperitoneally with protocatechuic or
tannic acid at 50 mg/kg
body weight five times during 14 days.
3-Methylcholanthrene (MC) was administered at 20 mg/kg
body weight on day 13 (the last treatment with phenolic compounds) and on day 14. Tissues were obtained from rats terminated 24 h after the last treatment. Western blot analysis with specific
antibodies showed significant differences in the effect of the phenolic compounds in the liver and kidney. In the liver,
protocatechuic acid significantly increased the constitutive GSTmicro, while
tannic acid reduced the GSTalpha
protein level by 60%. Both plant
phenols decreased all classes of constitutive GST
isozymes in the kidney including GSTpi, and also the MC-induced GSTalpha and/or pi
protein levels. These results, as well as our previous reports, suggest that protocatechuic and tannic
acids interfere with the pathways related to
xenobiotic toxicities and
carcinogenesis. This effect may be important for chemoprotective activity of these plant
phenols.