Related Experiment Video
Updated: Aug 13, 2026

Formation of Covalent DNA Adducts by Enzymatically Activated Carcinogens and Drugs In Vitro and Their Determination by 32P-postlabeling
Published on: March 20, 2018
The B-vitamin group and the activity of hepatic microsomal mixed-function oxidases of the growing Wistar rat
Abstract:
1. Male Wistar rats were given isoenergetic, semi-synthetic diets deficient in thiamin, riboflavin, pyridoxine or all the B-vitamins. 2. In rats given these deficient diets the 'sleeping time' induced with pentobarbital (PB) and the 'paralysis time' with zoxazolamine (Zz) were prolonged. 3. The tolerance effect against both drugs was nearly independent of the levels of B-vitamins in the diets. 4. In preparations from vitamin-B deficient animals the activities of the following hepatic microsomal enzymes were reduced: the aliphatic hydroxylase of PB, the aromatic hydroxylases of aniline (EC 1.14.14.1) and of Zz, the N-demethylase of aminopyrine, the UDP glucuronyltransferase (EC 2.4.1.17) of p-nitrophenol. The reactions most influenced were those of 'type-1' substrates, particularly those involving the hydroxylases. 5. The effects observed were caused mainly by deficiency of riboflavin and to a lesser extent of thiamin or pyridoxine.
Related Concept Videos
Drug Metabolism: Phase I Reactions
Phase I Reactions: Oxidation of Aliphatic and Aromatic Carbon-Containing Systems
Oxidation reactions are fundamental in aromatic carbon-containing systems. An example is the hydroxylation of phenobarbital, a process that transforms it into...
Factors Affecting Drug Biotransformation: Biological
Species differences: Variations in enzyme systems across species can cause disparities in drug metabolism. For instance, humans may metabolize certain drugs faster than rodents, altering therapeutic effects.
Strain differences: Genetic variations within a species can result in differing enzyme activity, impacting drug response and toxicity. For example, some mouse strains may...
Effect of Hepatic Disease on Pharmacokinetics: Pathophysiologic Assessment and Liver Function Test
Pharmacogenetics of Phase I Enzymes: Cytochrome P450 Isozymes
Bioactivation and Tissue Toxicity

