The cytochrome P450(P450) are a large group of constitutive and inducible heme-containing enzymes, which have a central role in the oxidative metabolism of a diverse range of xenobiotics. The majority of chemical carcinogens require metabolic activation before they interact with cellular macromolecules and can cause cancer initiation. The xenobiotic-metabolizing machinery contains two main types of enzymes : the phase I P450 mediating oxidative metabolism, and phase II containing enzymes. Activity of some enzymes implicated in the metabolism of carcinogens presents a great variability between individuals due to the existence of a polymorphism in gene coding for P450. Individual P450s, especially CYP1B1, are overexpressed in different types of tumors. The increased expressons of P450s in tumors is highly significant and is important for understanding rumor development and progression. The tumor-specific expression of P450s provides the basis for the development of movel diagnostic and therapeutic strategies.

Binding of clathrin assembly protein to clathrin triskelia induces their assembly into clathrin-coated vesicle in neurons. The clathrin binding protein is a neuronal-specific, synapse associated protein that is expressed nonuniformly in rat brain. We isolated two cDNAs, encoding the novel clathrin assembly protein, which has a 73% amino acid homology compared with that of AP180 protein when translated into amino acids. The deduced molecular weight is 64kD. The N-terminal domain harbouring clathrin binding site is very similar to that of AP180, and the C-terminal domain is much more different with that of AP180, which suggests that the novel protein mediates the assembly of clathrin and its regulatory role in the release of secretory vesicle.

The metabolism of drug and arachidonic acid(AA) by diabetic rat ocular tissues was studied. Little information is available on drug metabolism enzymes in ocular tissues. I investigated the presence of various cytochrome P-450 isoenzymes by measuring different drug metabolizing enzymes. i.e., 7-ethoxycoumarin-0-deethylase and benzphetamine demethylase activities in cornea and choroid, retina or sclera.

This results demonstrate that choroid, retina or sclera possess the highest activities of drug metabolizing enzymes. The highest activities of 7-ethoxycoumarin-0-deethylase and benzphetamine demathylase were found in choroid, retina or sclera. The highest activities of drug metabolizing enzyrnes is accompanied by high activity of NADPH cytochrome P-45O(C) reductase, an integral component of this enzyme study. The choroid, retina or sclera possesses the high activity of metabolizing arachidonic acid to biologically active compounds, whereas the cornea has tow activity of metabolizing arachidonic acid. A form of cytochrome P-450 has appear rat ocular tissues in diabetes and the effect of diabetes on ocular tissues cytochrome P-450 expression can be reversed by insulin treatment.

The specialized location of cytochrome P-450 isozymes in ocular tissues suggests a physiological function related to activation of endogenous compounds such as arachidonic acid, in addition to detoxifiaction of drugs. Thus, the choroid, retina or sclera is the site of metabolism and detoxification of drugs are carried to ocular tissues via circulating blood.

Butylated hydroxyanisole(BHA) has been shown to decrease the toxicological and carcinogenic potential of a variety of chemicals. One possible mechanism for chemoprotection is that BHA increases intestinal UDP-glucronosyltransferase activity and thereby enhances the elimination of the toxicants. Given that I.P injection is major route of xenobiotic exposure, we have investigated the action of BHA and BHT on glucuronidation capacity in the liver of rats. Simple injection of BHA(100mg/kg or 200mg/kg) and BHT(100mg/kg or 200mg/kg) produced a significant increase in microsomal glucuronidation. Futhermore, the concentration of UDP-glucuronic acid, the co-substrate required for glucuronidation reaction was increased almost 2-fold. Administration of BHA and BHT also increased UDP-glucose concentration and UDP-glucose dehydrogenase activities approximately 2-fold. These findings show that BHA and BHT administration increase hepatic glucuronidation capacity and suggest that BHA and BHT may enhance the biotransformation of xenobiotics, and hence excretion, of a variety of carcinogen and or toxins is potentially very important.

UDP-Glucuronosyltransferase(UDPGT) activity was studies in hepatic microsomal preparation from rats treated with nifedipine. The substrates 1-naphthol, P-nitrophenol, 4-methyl-umbelliferone and bilirubine were used. With 1-naphthol, nifedipine 2 and 4 weeks treatment caused 6- and 7.3-fold, respectively, increase in activity over the control value. With 4-methylumbelliferone, nifedipine 2 and 4 weeks treatment caused 5- and 6-fold increase in activity over the control value. With P-nitrophenol, nifedipine 2 and 4weeks treatment caused both approximately 3-fold increase in activity over the control value. However bilirubin-UDPGT activity was not affected by this inducer effects of nifedipine on the hepatic monooxygenase system in rats were investigate. P-Nitroanisole-O-demethylase, NADPH-cytochrome C reductase activity and cytochrome P-450 content in nifedipine treated rats were significantly increased to 390, 290 and 150% of control rats, respectively.

The selectivity of nifedipine of UDP-glucuronosyltransferase was investigated in rat liver microsomes and compared with their effect on monooxygenase reactions. Similart o 3-meth-lycholanthrene-type selectively stimulated the glucuronidation induced both UDPGT₁ and monooxygenase activity, probably through a common receptor protein.

Maternal ingestion of alcohol produce not only change of drug metabolism but also proliferation of hepatic smooth endoplasmic reticulum and many developmental defects of the central nervous system.

The present investigation examined the effects of maternal consumption of alcohol during pregnancy and/or lactation the activities of electron transfer components, mixed function monooxygenase, UDP-glucuronosyltransferase and lipid peroxidation of neonatal rat liver microsomes. Normal group consisted of neonatal rats whose mothers received standard chow and water. The subject of experimental group were neonatal rats whose mothers were exposed to alcohol during pregnancy and lactation(3 weeks).

The results were obtained as follows :

The activities of the electron transfer system, such as cytochrome P-450, NADPH-cytochrome C reductase were increased in hepatic microsomes of experimental group.

The activities of the mixed function monooxygenase, p-nitroanisole-O-demethylase and the conjugated enzyme, UDP-glucuronosyltransferase were increased in hepatic microsomal experimental group. There was no significant differences between the formation of lipid peroxide of normal and experimental group.

These results suggest that prenatal exposure to alcohol are influenced by disturb of liver microsomal drug metabolism, especially during the fetal period.

The effect of intraperitonelly administered higenamine on the cytochrome P -450, b₅, P-nitroanisole-O-demethylase and lipid peroxidation in the rat hepatic microsomes were determined. The following results were obtained ; 1) The intraperitonelly administered higenamine increased contents of rat hepatic microsomal cytochrome P-450 and b₅. 2) The principal role of cytochrome P-450 in mixed function oxidase reactions includes hydroxylation of various drugs, fatty acids, steroids, pesticides and carcinogens. The increased cytochrome P-450 induced by higenamine decreased on the both AAF of N-hydorxylation and Ring-hydroxylation. 3) Activity of P-nitroanisole-O-demethylase in hepatic microsomes with higenamine was decreased accorting to incresed dosage of higenamine. 4) The formation of lipid peroxides was increased according to increased dosage of higenamine.

Lipoprotein cholesterol and triglyceride levels have been determined innormal and diabetes. The abnormalities of lipoprotein were investigated by SDS-polyacrylamide gel electrophoresis in the serum and the 3 major lipoprotein classes for diabetes. HDL cholesterol levels were lower in the diabetes compared to the normals. VLDL triglyceride levels also elevated in the diabetes. There were significant shifts in the distribution of lipoprotein cholesterol, with an increase in LDL cholesterol and decrease in HDL cholesterol. The results of this study suggest that diabetes may be associated with changes in both lipoprotein triglyceride and cholesterol levels. The electrohoretic patterns of VLDL and HDL in diabetes showed the abnormal pattern in comparison to normal.

Ethanol enhances the activity of microsomal enzyme system and lipid peroxidation. We observed the effect of chronic ethanol administration on cytochrome P-450 level and lipid peroxidation in rat liver microsome. The results were as follows : 1) When rats were administered with ethanol, the level of microsomal cytochrome P-450 was decreased and lipid peroxidation did not change significantly. 2) When vitamin A and E were added incubation medium in each group, lipid per-oxidation was decreased significantly.

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• Effects of Chronic Consumption of Liquor prepared with Gastrodiae rhizoma on Antioxidant Activity in Brain Tissue of Rats
  In-Jeong Yun, Hyun-Joo Kong, Jung-Hyeon Jang, Kyung-Mi Yang
  Journal of the East Asian Society of Dietary Life.2016; 26(6): 531.     CrossRef

After rats were treated with CC1₄, phenobarbital and artemisia messes-schmiaiana var viridis(artemisia), hepatic microsomal cytochrome P-450, cytochrome b₅ and lipid peroxidation were investigated. When vitamin A, C and E were added incubation medium in each group respectively, lipid peroxidation was observed. The results were as follows. 1) When administrated with CC1₄ in rats, the contents of total microsomal cytochrome P-450 and cytochrome b₅ were decreased by 58% and 36%, respectively. And lipid peroxidation was decreased to by 6%. 2) When administrated with phenobarbital and artemisia. in rats respectively, the contents of total microsomal cytochrome P-450 and cytochrome b₅ were increased by 25 to 135%. And lipid peroxidation was increased by 30 to 57%. 3) When administrated with CC1₄ and phenobarbital or artemisia. in rats, the contents of total microsomal cytochrome P-450 and cytochrome b₅ were increased by 8 to 35%. And lipid peroxidation was increased by 4 to 14%. 4) When vitamin A, C and E incubated in each group in each group in vitro, lipid peroxidation were decreased by 3 to 87%. And th higher concentrations of vitamin A, C and E were, the more lipid peroxidation was decreased. These results indicate that vitamin antioxidants can prevent lipid peroxidation in CC1₄, phenobarbital, CC1₄ with phenobarital. artemisia. and CC1₄ with artemisia.-pretreated rat liver microsomes.

We observed the effect of the administration of vitamin A,C and E with β-naphthoflavone and piperonyl butoxide on cytochrome P-450 level and lipid peroxidation in rats liver. The level of hepatic cytochrome P-450 decreased after vitamin A,C and E was administration. In contrast, β-naphthoflavone, when administered with vitamin A,C and E, the increase of cytochrome P-450 was prevented. Lipid peroxidation was decreased after vitamin A, C, and E was administered. Moreover when β-naphthoflavone was administered together with vitamin A, C and E lipid peroxidation was not increased. When piperonyl butoxide was administered together with vitamin A,C and E, both cytochrome P-450 and lipid peroxidation were decreased. These results indicate that vitamin antioxidants can prevent lipid peroxidation by a cytochrome P-450 dependent terminal oxidase system in rat liver microsomes.

The principal role of cytochrome P-450 in many other mixed function oxidase reactions including hydroxylations or oxidative dealkylations of various drugs, fatty acids, steroids, pesticides, and carcinogens. In order to elucidate the effect of various vitamin antioxidants on hepatic microsomal cytochrome P-450 and AAF hydroxylation, vitamin antioxidants, including vitamiin A acetate, L-ascorbic acid and DL-α-tocopherol were administered to rats. The results of this study show that the inhibition of cytochrome P-450 level and AAF hydroxylation by vitamin antioxidants may be related to their ability to prevent the in vivo activation of AAF to carcinogenic N-hydroxylation. Vitamin antioxidants, because of their effectiveness in inhibiting chemical carcinogenesis, may become useful chemoprophylatic agents against environmental carcinogens.

We have investigated in rat liver whether different forms of cytochrome P-450 are alterated in hepatic disorders associated with impaired drug metabolism. Total hepatic cytochrome P-450 is decreased after either bile duct ligation or the administration of estradiol. In contrast, phenobarbital administrated alone increase hepatic content of cytochrome P-450, and when administrated with estradiol the reduction in cytochrome P-450 was prevented. Four forms of microsomal cytochrome P-450 apoproteins, ranging in molecular weight from 50 000 to 58,000, were tentatively identified in a sodium dodecyl sulfate(SDS)-6M urea polyaocrylamide gel electrophoresis system. Phenobrbital administration icreased primarily band IV(50,000 daltons). Bile duct ilgation was associated with a marked reduction in bands II and III while bands II and III were decreased with estradiol benzoate administration. Sumultaneous administration of phenobarbital and estradiol demonstrated a return of band I and an increase in density of bands III and IV. Simultaneous administration of cholic acid and estradiol demonstrated a return of band I and not altered in band III and IV. These studies support the hypothesis that multiple forms of cytochrome P-450 are present in liver microsomal membranes and that alterations in spenific apoproteins may be associated with an increase or a decrease in the functional properties of cytochrome P-450.

The effects of vitamin B complexes on both ring and N-hydroxylation of 2-ace-tylaminofluorene by rat hepatic microsomal fraction were studied.

In the presence of thiamine-Hcl during incubation, the total hydroxy-AAF was increased by 50.3%. 0.1mM and 1.0mM riboflavin inhibited only total hydroxy-AAF with 56.7% and 85.0 whereas N-hydroxy AAF was increased to some extent. 1.0mM niacin did not have much effect on the total hydroxy-AAF, but 0.1mM niacin decreased the total dydroxy-AAF by 28.6%. Presence of p-amino-benzoic acid, calcium pantothenate, pyridoxal-Hcl or vitamin B₁₂ inhibited the total hydroxy-AAF to some extent. But the radio of ring-and N-AAF hydroxylation was not changed by these vitaminn B complexes.

Our present results suggest that vitamin B complexes were not effective in vitro metabolism of 2-AAF to N-hydroxy AAF(activation step of AAF) by a cytochrome p-450 dependent mixed function oxidase system.

We have investigated the effect of administation of exogenous cholic acid whether total hepatic cytochrome P-450 and b5 are altered in the bile duct-ligated rats.

The effect of administration of exogenous cholic acid on the hepatic microsomal mixed-fuction oxidase system is various according to the administration route, dosage and date after administration.

In normal rats, 1ml of 0.5m mol cholic acid solution per 100g body weight administrated intravenously increases hepatic content of cytochrome P-450 and b5 on the third to fifth days after injection.

Total hepatic cytochrome P-450 and b5 are decreased after either bile duct ligation or the administration of ethinyl estradiol. In contrast when cholic acid is adminstrated simultaneously with bile duct ligation, the reduction in cytochome P-450 is relativery prevented.

These effects are similar to the potential of phenobarbital for reversing the bile duct ligation-associated decrease in all components of the mixed function oxidase system.

No abstract available.

Male Wistar rats maintained for a period of 6 weeks on a basal vitamin E-deficiency diet consisting of 70% sucrose, 20% vatamin-free casein, 4% tocopherol, stripped lard, 4% salt mixture, and 2% tocopherol-free vitamin fortification mixture were used to compare two sets of commonly used salt mixture(salt mixture USP XIV versus Briggs' salt mixture). Among the rats maintained on the deficient diets for 6 weeks, only that received the combination of Briggs' salt mixture showed a significantly lower level of hepatic catalase activity, cytochrome P-450, and b₅ compared to the corresponding control animals. Since the most striking differences in these diets are in their contest of iron, it appears that these two dietary constituents may intact in modulating the effect of vitamin E on hepatic hemoproteins.

Our studies are concerned with cytochrome P-450 content and 2-acetylaminofluorene N-and ring-hydroxylation by thiamine deficient rat liver microsomes. Incubation medium contained 100mM HEPES buffer pH 7.8, 2mM NADPH, 100mM KF, 100nM [¹⁴C]-AAF and microsomal protein. After 30min, incubation at 37℃, ring and N-hydroxy-9-¹⁴C-AAF formations are assayed by radioactivity measurements after paper chromatography separation. The concentration of cytochrome P-450 is elevated in microsomes from rats fed the deficient diet. It appears that the thiamine deficient rat liver is capable of producing effects on the drug hydroxylation enzymes.