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Dietary ascorbic acid and hepatic mixed function oxidase activity in the guinea pig
Biochemical Pharmacology
|January 1, 1983
Summary
Vitamin C affects liver enzymes. Ascorbic acid deficiency impairs drug metabolism, while excess vitamin C minimally impacts cytochrome P-450 and drug metabolism, but uniquely affects cholesterol 7 alpha-hydroxylase.
Area of Science:
- Biochemistry
- Pharmacology
- Nutritional Science
Background:
- Hepatic mixed function oxidase (MFO) system is crucial for xenobiotic and endogenous compound metabolism.
- Ascorbic acid (vitamin C) is an essential nutrient with known antioxidant properties.
- The impact of chronic ascorbic acid deficiency or excess on MFO activity requires detailed characterization.
Purpose of the Study:
- To investigate the effects of chronic ascorbic acid deficiency and excessive intake on guinea pig hepatic MFO activity.
- To determine how vitamin C status influences the metabolism of various drugs and cholesterol.
- To identify specific enzymes within the MFO system sensitive to dietary ascorbic acid levels.
Main Methods:
- Guinea pigs were fed diets with controlled, deficient, or excessive amounts of ascorbic acid.
- Hepatic cytochrome P-450 content was measured.
- The metabolism of model drugs (aniline, aminopyrine, ethoxycoumarin, benzphetamine, ethylmorphine) was assessed.
- Cholesterol 7 alpha-hydroxylation activity was quantified.
Main Results:
- Excessive ascorbic acid intake caused a minor increase in hepatic cytochrome P-450 but did not alter basal or phenobarbital-induced MFO activity.
- Chronic ascorbic acid deficiency led to reduced metabolism of several drugs, including aniline, aminopyrine, ethoxycoumarin, and benzphetamine.
- Cholesterol 7 alpha-hydroxylation was depressed by both vitamin C deficiency and excess, unlike drug metabolism.
- Cholesterol 7 alpha-hydroxylase demonstrated unique sensitivity to dietary ascorbic acid levels.
Conclusions:
- Dietary ascorbic acid levels significantly influence hepatic drug metabolism, particularly under deficiency conditions.
- Cholesterol 7 alpha-hydroxylase is uniquely sensitive to both inadequate and excessive vitamin C intake.
- These findings highlight the critical role of vitamin C in maintaining metabolic homeostasis, especially concerning cholesterol metabolism.