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Vitamin K1 amplification of benzo(a)pyrene metabolism in chick embryos
Insights
Vitamin K1 (K1) can enhance benzo(a)pyrene (BP) metabolism by increasing arylhydrocarbon hydroxylase (AHH) and cytochrome P-450, potentially aiding BP-induced mutagenicity.
Area of Science:
- Biochemistry
- Toxicology
- Pharmacology
Background:
- Benzo(a)pyrene (BP) is a polycyclic aromatic hydrocarbon known for its mutagenic and carcinogenic properties.
- Metabolism of BP involves Phase I (oxidation) and Phase II (conjugation) enzymatic reactions.
- Chick embryos provide a suitable model for studying xenobiotic metabolism.
Purpose of the Study:
- To investigate the effect of vitamin K1 (K1) on benzo(a)pyrene (BP) metabolism in chick embryos.
- To assess the impact of K1 on key enzymes involved in BP detoxification, including arylhydrocarbon hydroxylase (AHH), cytochrome P-450, glutathione (GSH), and glutathione S-transferase (GST).
Main Methods:
- Seventeen-day-old chick embryos were used as the experimental system.
- BP was administered via air sac injection.
- Vitamin K1 was administered 24 hours prior to BP injection.
- Levels of AHH, cytochrome P-450, GSH, and GST activity in the liver were measured.
Main Results:
- BP injection led to increased AHH and P-450 levels and decreased GSH levels.
- Pre-treatment with K1 resulted in decreased GST activity and augmented AHH induction compared to controls.
- Ubiquinone showed a less significant effect on BP metabolism than K1 at equimolar concentrations.
Conclusions:
- Vitamin K1 augments BP metabolism (Phase I) and decreases Phase II conjugation, suggesting an adjuvant role in BP-induced mutagenicity and carcinogenicity.
- K1's effect on BP metabolism is more pronounced than that of ubiquinone.
- These findings highlight K1's potential role in modulating the toxicological effects of environmental carcinogens.
Abstract:
Seventeen-day-old chick embryos were used as a test system to assess the effect of vitamin K1(K1) on benzo(a)pyrene (BP) metabolism as measured by the induction of arylhydrocarbon hydroxylase (AHH) and cytochrome P-450 and the levels of glutathione (GSH) and glutathione S-transferase (GST) in liver. Twenty-four hours after injection of BP into the air sac there was a sharp rise in AHH and P-450 and a drop in GSH. When K1 was injected 24 hr prior to BP there was a decrease in GST activity as compared with the control plus an augmented increase in AHH induction. This augmentation in BP metabolism (Phase I) together with a concomitant decrease in at least one mechanism of Phase II conjugation is in keeping with other evidence that K1 can play an adjuvant role in BP induced mutagenicity and carcinogenicity. Ubiquinone has a much lesser effect on BP metabolism than does K1 in equimolar concentration.
