Current methods of cytochrome P450 analysis

Current review describes recent approaches of cytochrome P450 concentration and activity evaluation. Special attention paid to modern methods of proteomic analysis such as electrophoresis and chromato-mass-spectrometry. Methods of targeted proteomic applicable for quantitative and qualitative study of P450s in biological samples as well as methods for the enzyme activity measurements are reviewed. Finally, data on correlation between certain P450 isoform content and its specific enzymatic activities were described and discussed in the review.

Effects of dietary zinc deficiency on the hepatic microsomal cytochrome P450 2B in rats

This study was conducted to investigate whether the effects of zinc deficiency on the in vitro and in vivo drug metabolism in rats results from an altered expression of hepatic microsomal P450, particularly P450 2B (2B), in rats. Three-week-old, male Wistar rats were randomly assigned to three groups: a zinc-adequate ad libitum (ZnAL), zinc-adequate pair-fed (ZnPF), and zinc-deficient (ZnDF) group. After 3 weeks on the diet, each dietary group was further divided into drug control and phenobarbital (PB, 100 mg/kg, 3 days, ip) group. Within the drug control group, total microsomal P450 concentration was lower in both ZnPF and ZnDF than in ZnAL. Zinc deficiency resulted in a decreased aminopyrine N-demethylase (AD) activity expressed per milligram protein, with no effect on benzphetamine N-demethylase (BD) activity. The constitutive level of 2B protein and mRNA was not affected by dietary treatments. The level of NADPH–P450 reductase in ZnDF was significantly higher than in ZnAL and ZnPF. PB treatment significantly induced total microsomal P450 concentration, AD and BD activities expressed per milligram protein, 2B protein and mRNA levels, and NADPH–P450 reductase level in all dietary groups. In summary, the constitutive level of AD activity, but not BD activity, was decreased in dietary zinc deficient rats. The constitutive levels of 2B protein and mRNA were not affected by dietary zinc deficiency. PB-induced expression of 2B, both transcriptionally and translationally, and the induction of AD and BD activity by PB were not affected by zinc deficiency in rats. Severe feed restriction had no effect on the levels of both constitutively and inductively expressed AD and BD activities, 2B protein, and 2B mRNA.Key words: dietary zinc deficiency, 2B protein and mRNA, 2B activity, induction of 2B, phenobarbital.

Effects of Hexachlorobenzene Feeding and Iron Overload on Enzymes of Haem Biosynthesis and Cytochrome P450 in Rat Liver

1. The effect of hexachlorobenzene feeding on liver δ-aminolaevulinate synthase, uroporphyrinogen decarboxylase and cytochrome P450 was studied at various time-intervals in siderotic and non-siderotic rats. 2. In the non-siderotic group hexachlorobenzene feeding led to a progressive decrease in liver uroporphyrinogen decarboxylase activity, accompanied by a progressive increase in δ-aminolaevulinate synthase activity. Cytochrome P450 concentrations were above normal throughout but fell toward the end of the experiment. 3. Similar but more marked changes were found in the siderotic animals. The fall in uroporphyrinogen decarboxylase activity occurred earlier and was significantly greater in these animals, whereas the increase in δ-aminolaevulinate synthase activity was consistently larger. Liver cytochrome P450 concentration also rose but to a lesser extent than that in the non-siderotic rats. 4. Hexachlorobenzene-induced porphyria would seem to be attributable to inhibition or inactivation of hepatic uroporphyrinogen decarboxylase. Hepatic siderosis has a synergistic effect with hexachlorobenzene on this enzyme and may exert additional effects by promoting cytochrome P450 turnover.