Cytochrome P450 modification by a new oxazine derivative with hypolipidemic activity

Plasma lipoprotein levels, related to atheromatosis, are influenced by liver function. Microsomal enzyme inducers are reported to modify serum lipoproteins and triglycerides. In this study, the effects of subchronic and acute treatment of rats with 3-(4-biphenyl)-3-n-propoxy-octahydro-1,4-pyrido[2,1-c]oxazine, a novel compound with hypolipidemic and antioxidant activities, on rat hepatic microsomal protein and total cytochrome P450, as well as on p-nitrophenol hydroxylase (CYP2E) and erythromycin N-demethylase (CYP3A) activities are examined. The subchronic treatment had no significant effect on liver weight, microsomal protein and total cytochrome P450. The acute administration lowered considerably cytochrome P450 content. The metabolic activities of CYP2E1 and CYP3A1/2 were not altered by the subchronic treatment, but were notably decreased after the single administration of 3-(4-biphenyl)-3-n-propoxy-octahydro-1,4-pyrido[2,1-c]oxazine. The inhibition of drug metabolism by 3-(4-biphenyl)-3-n-propoxy-octahydro-1,4-pyrido[2,1-c]oxazine cannot be completely correlated with the modification of plasma cholesterol, triglycerides and LDL cholesterol, although published data connect microsomal enzyme induction with a decrease of these parameters. This discrepancy could be attributed to the different biochemical events involved in enzyme induction and inhibition.     

Comparative biochemical and morphometric changes associated with induction of the hepatic mixed function oxidase system in the rat.

This study characterized the induction of the rat hepatic cytochrome P-450-dependent mixed function oxidase system by SK&F 86002 [6-(4'-fluorophenyl)-5-(4'-pyridyl)-2,3-dihydroimidazo-(2,1-b)thia zole], an inhibitor of both the cyclooxygenase and 5-lipoxygenase pathways of arachidonic acid metabolism. The induction characteristics of SK&F 86002 were compared to those of the classical inducer, phenobarbital, and morphological features of both SK&F 86002 and phenobarbital induced hepatocellular hypertrophy were quantitated. Rats were administered either SK&F 86002 (6, 18, or 60 mg/kg/day, po) or phenobarbital (8, 24, 80 mg/kg/day, ip) for 3 or 14 consecutive days. Liver to body weight ratio, total hepatic microsomal protein and cytochrome P-450 content, ethoxycoumarin-O-deethylase (ECOD) and leukotriene B4(LTB4) omega- and omega-1 hydroxylase were measured. Ultrastructural morphometry of the liver from control, and high dose SK&F 86002 (60 mg/kg/day) and phenobarbital (80 mg/kg/day) treated rats was completed. On day 3, phenobarbital increased liver to body weight ratio but only at the 80 mg/kg/day dosage; microsomal protein content was unchanged. ECOD activity increased in a dose-dependent fashion. LTB4 omega- and omega-1 hydroxylase activities were unaffected. Administration of SK&F 86002 for 3 days increased the liver to body weight ratio at both the 18 and 60 mg/kg/day dosage; microsomal protein content was unchanged. ECOD activity was significantly increased by the 60 mg/kg/day dosages of SK&F 86002. On day 14, phenobarbital increased the liver to body weight ratio and microsomal protein content but again only at the 80 mg/kg/day dosage. Cytochrome P-450 content was increased by all dosages.(ABSTRACT TRUNCATED AT 250 WORDS)     

Zonation of the adrenal cortex. III. Distribution of cytochrome P-450 in the zona glomerulosa of the bovine adrenal cortex.

A microsomal fraction was obtained from the zona glomerulosa of the bovine adrenal cortex. Glucose-6-phosphate activity of the fraction was found to be much lower than that of the liver. Contents of RNA and phospholipids, besides electron microscopic findings, of the fraction also indicate that it is rich in smooth-surfaced endoplasmic reticulum. Distribution of cytochrome P-450 in the zona glomerulosa was studied using various fractions including the microsomal fraction described above. The amount of cytochrome P-450 in mitochondria and that in microsomes were determined to be 0.73 and 0.32 nmoles/mg protein, respectively. The CO-difference spectrum was affected not only by the concentration of added deoxycholate but also by the incubation time after addition. Approximately 40-50% of cytochrome P-450 in the samples were converted to cytochrome P-420 within 20-30 seconds of incubation with deoxycholate.     

Effects of aging and caloric restriction on hepatic drug metabolizing enzymes in the Fischer 344 rat. I: The cytochrome P-450 dependent monooxygenase system

The effects of long-term caloric restriction on the hepatic cytochrome P-450 dependent monooxygenase system were investigated in the 22-month-old Fischer 344 rat. Caloric restriction decreased the age-related changes in hepatic testosterone metabolism, which are associated with demasculinization of the liver. Caloric restriction also increased hepatic microsomal testosterone 6 beta-hydroxylase, lauric acid 12-hydroxylase and 4-nitrophenol hydroxylase activities over corresponding values in both ad libitum fed 22-month and 60-day-old control male rats. This suggests that cytochrome P-450 isozymes, P-450 pcn1&2, P-452 and P450j may be induced by caloric restriction. Such changes in cytochrome P-450 isozyme profiles could result in altered carcinogen activation, radical formation or drug detoxication in the calorically restricted rat.     

The effect of IFN-alpha-Con1 on hepatic cytochrome P-450 and protein synthesis and degradation in hepatic microsomes.

Interferon and its inducers are well known to depress drug biotransformation in the liver by decreasing the levels of cytochrome P-450 in that organ. We now report that IFN-alpha-Con1, which was constructed from the most frequently observed amino acid sequences in human alpha-interferon subtypes, causes a loss in cytochrome P-450 which could be prevented by pretreating animals with either puromycin or actinomycin D. This suggests that the loss in drug biotransformation is mediated via the production of an intermediate protein. When the turnover of microsomal protein was examined this interferon appeared to depress the synthesis of proteins with molecular weights 46-60 kd and had little effect on the synthesis of other proteins. The in vitro translation of proteins of molecular weights 45-60 kd was also depressed in an in vitro translation system using mRNA isolated from the livers of interferon treated hamsters. Interferon had no effect on the degradation of microsomal proteins of all molecular weights. It is concluded that interferon probably depresses the levels of cytochrome P-450 in the liver by decreasing the synthesis of the apoprotein and that interferon has little effect on the degradation of the hemoprotein.     

Deficiency of hepatic lipase activity in post-heparin plasma in familial hyper-alpha-triglyceridemia

Hyper-alpha-triglyceridemia is a rare dyslipoproteinemia characterized by a pronounced increase in the concentration of triglycerides in the plasma high density lipoprotein (HDL) fraction. One case with this condition, an apparently healthy 61-year-old man, has been studied. Additional lipoprotein abnormalities were present, such as abnormally cholesterol-rich very low density lipoproteins (VLDL) with retarded electrophoretic mobility (beta-VLDL) and triglyceride enrichment of low density lipoproteins (LDL). The patient's plasma concentration of apolipoproteins A-I, A-II and B were normal and those of C-I, C-II, C-III and E were elevated. No abnormal forms of the soluble apolipoproteins of VLDL and high density lipoproteins (HDL) were found after analysis by isoelectric focusing. Lecithin:cholesterol acyltransferase activities, plasma cholesterol esterification rates and lipid transfer protein activities were normal. Post-heparin plasma activity of hepatic lipase was virtually absent and that of lipoprotein lipase was reduced by 50%. In plasma of this patient, HDL was almost exclusively present as large triglyceride-rich particles corresponding in size to particles of the HDL2 density fraction. The only brother of the patient also had hyper-alpha-triglyceridemia together with the other lipoprotein abnormalities described for the index case and deficiency of postheparin plasma activity of hepatic lipase. The findings presented below support the hypothesis that one primary function of hepatic lipase is associated with degradation of plasma HDL2. Deficiency of this enzyme activity thus causes accumulation of HDL2 in plasma leading to hyper-alpha-triglyceridemia. The results further suggest that the abnormal chemical and electrophoretic properties of VLDL and LDL in plasma from the patient, reminiscent of type III hyperlipoproteinemia, are secondary to the lack of the action of hepatic lipase on the HDL particles.     

Resistance of different forms of cytochrome P-450 of rat liver to factors destabilizing the microsomal membrane

The effect of factors destabilizing the membrane of the liver microsomes on the spectral properties of cytochrome P-450 (P-448) was investigated in intact rats and rats receiving phenobarbital (PB) or 3-methylcholanthrene (MC). Considerable resistance of microsomes induced by PB and MC to enzymic and nonenzymic peroxidation of polyunsaturated fatty acids of membrane phospholipids was discovered. A clear difference was shown in the sensitivity of cytochrome P-448 and cytochrome P-450 of intact rats and rats receiving PB to in vitro treatment with sodium deoxycholate. The results indicate structural changes in the microsomal membrane during induction by PB and MC, which are two different types of inducers of the monooxygenases of the liver.Institute of Clinical and Experimental Medicine, Siberian Branch, Academy of Medical Sciences of the USSR, Novosibirsk. (Presented by Academician of the Academy of Medical Sciences of the USSR V. P. Kaznacheev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 5, pp. 553–555, May, 1977.     

Role of lipoproteins transporting lipophilic xenobiotics in the induction of microsomal monooxygenases

We studied the effects of lipopolysaccharide on activity of liver microsomal enzymes against the background of xenobiotics treatment. Against the background of lipopolysaccharide stimulation of macrophages we observed in vivo activation of cytochromes P-450 1A subfamily in liver microsomes with Arochlor 1254, but not induction of cytochrome P-450 2B subfamily with phenobarbital.     

Hepatic microsomal cytochrome P450 system during experimental hookworm infection

Experimental infection of golden hamsters with the hookworm, Ancylostoma ceylanicum, caused a profound decline in the hepatic microsomal cytochrome P450 content. Concomitant decrease was also noticed in aminopyrine N-demethylase and benzo[a]pyrene hydroxylase activities. However, aniline hydroxylase activity was only marginally elevated during the infection. Microsomal markers, viz., cytochrome b5, NADH-cytochrome-c reductase, and glucose-6-phosphatase, were not significantly altered. Hepatic tissue exhibited an accumulation of lipids, especially phospholipids, triglycerides, and cholesterol, resulting in fatty necrosis around the central vein region. Isolated hepatic microsomes showed a decrease in phosphatidylcholine content. Impairment in hepatic mixed function oxidase (MFO) activities was further confirmed by prolongation in hexobarbital sleeping time and zoxazolamine-induced paralysis. The hepatic MFO system of A. ceylanicum-infected hamsters responded qualitatively and quantitatively in a manner similar to that of control hamsters, upon stimulation with selective chemical inducers like phenobarbitone and 3-methylcholanthrene. Kinetic and in vitro substrate binding studies revealed that for aminopyrine the substrate affinity and the maximum enzyme activity (Vmax) were decreased, while for aniline the binding affinity was decreased and the binding capacity was enhanced. Results indicate specific/selective impairment of the hepatic microsomal cytochrome P450 system during hookworm infection and may have many practical implications in toxicology and pharmacology.     

Angiotensin-converting enzyme gene polymorphism,lipids, and apolipoproteins in menopausal women on hormone replacement therapy

This study investigated the frequency of angiotensin-converting enzyme (ACE) genotypes, concentrations of total cholesterol (T-C), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), lipoprotein Lp (a), Established Risk Factor (ERF) ratio (total cholesterol/HDL-C), apolipoproteins A-I, A-II, apoBand apoE in 134 menopausal women aged 49.62 +/- 4.83 on oral hormone replacement therapy (HRT) (2 mg 17 beta estradiol plus 1 mg norethisterone acetate/day), during (mean +/- SD) 15.77 +/- 9.94 months. ACE genotypes of 134 menopausal women showed DD genotype in 48 (36%), ID genotype in 59 (44%), and II genotype in 27 (20%) women, with the mean body mass index (BMI) (kg/m2) of 26.34 +/- 4.02, systolic blood pressure (mm Hg) of 145.71 +/- 23.32, diastolic blood pressure of 95.28 +/- 12.88, pulse rate of 77.76 +/- 13.81, positive family history of myocardial infarction (MI) (23%) and stroke (22%); 26% were smokers and 6% consumed alcohol regularly. The mean levels of TC (mmol/l) were 5.72 +/- 1.25, TG (mmol/L) 1.63 +/- 0.82, HDL-C (mmol/L) 1.15 +/- 0.29, LDL-C (mmol/L) 3.98 +/- 1.31, lipoprotein Lp(a) (g/L) 0.16 +/- 0.24, ERF ratio 5.35 +/- 1.90, apolipoproteins (g/L): A-I 1.83 +/- 0.39, A-II 0.57 +/- 0.12, apoB 0.92 +/- 0.31, and apoE 0.08 +/- 0.04. The highest mean levels of T-C 5.89 +/- 1.40, TG 1.67 +/- 0.96, LDL-C 4.15 +/- 1.60, lipoprotein Lp(a) 0.19 +/- 0.25) apoB 0.95 +/- 0.32 and ERF ratio 5.46 +/- 2.24 were found in ID genotype, while in DD genotype HDL-C 1.11 +/- 0.28 and apo A-I 1.78 +/- 0.34 were lowest. In II genotype, the levels of apo A-II 0.56 +/- 0.11 were lowest and of apoE 0.09 +/- 0.05 highest. According to DD, ID and II genotypes and lipid, lipoprotein Lp(a), ERF ratio and apolipoprotein concentrations, there were no statistically significant differences between groups. ERF ratio in DD genotype showed a positive correlation with TG (r = 0.59) and LDL-C (r = 0.57), a slight positive correlation with apoB (r = 0.40), and a strong negative correlation with HDL-C (r = -0.73). ERF in ID genotype showed a strong negative correlation with HDL-C (r = -0.73), strong positive correlation with TG (r = 0.70), and T-C (r = 0.58), and slight positive correlation with LDL-C (r = 0.36) and alcohol abuse (r = 0.34). In II genotype, ERF ratio showed a strong positive correlation with LDL-C (r = 0.73), T-C (r = 0.70) and apoE (r = 0.58), slight positive correlation with apoB (r = 0.46) and TG (r = 0.36), and negative correlation with HDL-C (r = -0.54). Matrix correlation of DD genotypes showed the highest positive correlation between T-C and LDL-C (r = 0.91) and apoE (r = 0.45), and negative correlation between HDL-C and ERF ratio (r = 77), and LDL-C and ERF ratio (r = 0.55). In ID genotype, T-C showed a strong positive correlation between LDL-C (r = 0.75) and ERF ratio (r = 0.63), TG and ERF ratio (r = 0.73), and negative with HDL-C (r = 0.53). In genotype II, T-C showed a strong positive correlation between LDL-C (r = 0.96), ERF ratio (r = 0.71), apoB (r = 0.66) and apoE (r = 0.46). LDL-C correlated positively with ERF ratio (r = 0.72), apoB (r = 0.61) and apoE (r = 0.48). These findings indicated the frequency of ACE genotypes to differ within the group of menopausal women. Analysis of ACE genotypes showed ID genotype to be most common among menopausal women. This result indicated their intermediate risk of coronary heart disease (CHD) and myocardial infarction (MI). It has been well established that an increased risk of MI is associated with high frequency of DD genotype, and a low risk with high frequencies of II genotype. In addition to ACE polymorphism analysis, assessment of lipid, apolipoprotein, and lipoprotein Lp(a) concentrations, and of ERF ratio provides further important parameters for better understanding of the risk factors for CDH in women. In the present study, assessment of the genetic, metabolic and environmental markers pointed to an intermediate risk of CHD in menopausal women on HRT, although the mechanism underlying the disease is not clear and well understood yet.     

Carbon tetrachloride hepatotoxicity in endotoxin tolerant and polymyxin B-treated rats

Gut-derived endotoxin has been implicated in the hepatotoxic effects of CCl4. The present study has investigated whether two procedures known to block LPS effects would alter the action of CCl4 to decrease hepatic cytochrome P-450 and microsomal drug-metabolizing activity. Administration of polymyxin B or induction of LPS tolerance were shown to attenuate the effect of CCl4 administration to increase SGOT and SGPT levels, signs of hepatic damage. Polymyxin B administration but not LPS tolerance caused a slight decrease in cytochrome P-450. In pretreated animals given CCl4, only those which had received polymyxin B showed a reduced effect of CCl4 to alter cytochrome P-450 level and activity. However, the apparent protective effect was of the same magnitude as the loss of cytochrome P-450 caused by polymyxin B itself. These results suggest that the ability of polymyxin B to ablate the CCl4 loss of P-450 might be due to a reduced metabolic activation of CCl4 by P-450 and not due to any anti-LPS activity. The results suggest that gut-derived LPS does not participate in the effect of CCl4 decreasing cytochrome P-450-mediated reactions. However, participation of LPS in other hepatotoxic effects of CCl4 is not excluded.     

Effects of ethanol on microsomal drug metabolism in aging female rats. I. Induction

The purpose of this study was to determine how aging affects the induction by ethanol or acetone of the hepatic microsomal monooxygenase system of female Fischer 344 rats. Young-adult, middle-aged and old rats (4, 14 and 25 months) were fed an ethanol-containing or control liquid diet for 15 days. Cytochrome P-450, cytochrome c reductase, aniline hydroxylase, nitrophenol hydroxylase, nitroanisole O-demethylase and benzphetamine N-demethylase activities were measured in hepatic microsomes. All of the drug metabolism activities except benzphetamine N-demethylase were 20-35% lower in old than in young-adult rats fed the control diet. In addition, the increase in drug metabolism produced by feeding the regular ethanol diet (36% of calories as ethanol) was 50-60% lower in the old rats. However, there was no difference in the magnitude of ethanol induction when ethanol intakes were matched. The effects of chronic acetone consumption (1.2g/day per kg body weight for 15 days) paralleled those of ethanol consumption, except that the extent of induction was greater with acetone. Acetone-induced levels of hepatic microsomal cytochrome P-450, nitrophenol hydroxylase, nitroanisole O-demethylase and aniline hydroxylase were similar in all three age groups. The results of this study indicate that induction of hepatic microsomal drug metabolism by ethanol or acetone is unaffected by the aging process.     

Turnover of hepatic cytochrome P-450 in experimental cholestasis

In mechanical experimental chllestasis, hypertrophy of smooth microsomal membranes was observed. In contrast to typical induction, the membranes were deficient in cytochrome P-450. The total cytochrome P-450 content of the liver, however, as determined in the liver homogenate remained unchanged. To clarify the mechanism of the development of cytochrome P-450 deficient membranes in cholestasis, the half life of the heme portion of cytochrome P-450, and the initial rate of synthesis of cytochrome P-450 and b₅ hemes were compared in bile duct ligated rats and in control animals after labeling the heme by injection of the precursor δ-[4-¹⁴C]aminolevulinic acid. The half lives were not significantly different, which eliminates the possibility that selective destruction of cytochrome P-450 has occurred. Depression of cytochromal heme synthesis was not observed. During mechanical cholestasis, the relative cytochrome P-450 deficiency is probably caused by proliferation of components of the endoplasmic reticulum other than the hemoprotein.     

Apolipoprotein B gene polymorphisms in ischemic heart disease and hypercholesterolemia: effects of age and sex

The association of polymorphic alleles of the apolipoprotein B gene (Insertion/Deletion-, Xbal-, MspI-, EcoRI-, and 3'-VNTR polymorphisms) with variation in lipid concentrations (total cholesterol (T-C), HDL cholesterol (HDL-C), and log-triglycerides (TG)) in plasma was studied in 259 men and 59 women with moderate hypercholesterolemia (T-C 5.5–8.0 mmol/l and TG < 2.5 mmol/l) and ischemic heart disease, especially in relation to the effect of sex and age. The XbaI and the Ins/Del polymorphic alleles were associated with variation in T-C, but only in patients below the 75th percentile for age. The XbaI and Ins/Del polymorphic alleles were synergistically associated with variation in T-C: the X+ and the Del alleles were associated with higher cholesterol concentrations. Younger male patients had the highest frequency of haplo-types including both the X+ and the Del alleles, but the most striking difference was a significantly higher frequency of haplotypes including both the X — and the Ins alleles in female and in older male patients. The heterogeneity of association of polymorphic alleles in the apolipoprotein B gene to complex traits like hypercholesterolemia and ischemic heart disease in this study could explain why in most studies the X+ allele has been associated with higher cholesterol levels, whereas the X — allele has been associated with symptomatic atherosclerosis. The results of our study emphasize the importance of age and sex in measured genotype association studies.     

冠心病患者血浆LCAT水平与HDL亚类组成的关系

 目的： 探讨冠心病 (coronary heart disease, CHD) 患者血浆卵磷脂胆固醇酰基转移酶 (lecithin cholesterol acyltransferase, LCAT) 与高密度脂蛋白 (high-density lipoprotein, HDL) 亚类分布的关系。方法：采用双向电泳-免疫印记法分析了73例正常对照者和144例冠心病患者HDL亚类的组成、含量及分布特征,用酶联免疫法测定其LCAT浓度。冠心病患者按血浆LCAT浓度进行四分位数（19.22、36.39和55.32 mg/L）分层（Q1：LCAT<19.22 mg/L; Q2：19.22≤LCAT<36.39 mg/L; Q3：36.39≤LCAT<55.32 mg/L; Q4：LCAT≥55.32 mg/L）。结果：随着LCAT浓度的降低,冠心病患者血浆总胆固醇（TC）、甘油三酯（TG）水平和载脂蛋白B-100/A-I(apoB-100/A-I)比值呈增加趋势,高密度脂蛋白胆固醇（HDL-C）和apoA-I水平呈减少趋势。与最高四分位数组相比,第三、第二和最低四分位数组中preβ1-HDL含量增加,HDL2a和HDL2b含量减少 (P<0.05或P<0.01)。与正常TC组比较,高TC组LCAT浓度降低,且preβ1-HDL含量增加,HDL2a 和HDL2b含量减少(P<0.01)。直线相关和多元回归分析中发现,血浆LCAT水平与preβ1-HDL浓度呈负相关,与HDL2a和HDL2b浓度呈正相关。结论：CHD患者血浆HDL颗粒呈变小趋势,并且随着LCAT水平的降低,其HDL颗粒的变小程度更加明显。     

A first British case of fish-eye disease presenting at age 75 years: a double heterozygote for defined and new mutations affecting LCAT structure and expression.

Fish-eye disease is a familial syndrome with corneal opacification, major high density lipoprotein (HDL) deficiency in plasma, significant cholesterol esterification in plasma on non-HDL lipoproteins, generally without premature coronary disease. This first British male case from unrelated British parents had infarcts when aged 49 and 73 years but was asymptomatic at age 81 years, with plasma cholesterol 4.3-7.1 mmol/litre, triglycerides 1.8-2.2 mmol/litre, HDL cholesterol < 0.1 mmol/litre, apolipoprotein A-I < 0.16 g/litre, lipoprotein(a) 0.61 g/litre. Cholesterol esterification was impaired using HDL-3 and A-I proteoliposomes but not using VLDL/IDL/LDL. The findings are those of LCAT deficiency with the classic fish-eye disease defect. Most of the 22 reported cases were homozygous or heterozygous for a Thr-Ile mutation at codon 123 of the lecithin:cholesterol acyltransferase (LCAT) gene. This patient was a double heterozygote for this mutation and a second new incompletely defined mutation affecting LCAT expression as defined by reduced mass and activity in plasma.     

Age-dependent alterations in the physicochemical properties of rat liver microsomes

Aging results in a significant decline in liver drug metabolism which is largely attributable to changes in the microsomal mixed function oxidase system. For example, the mixed function oxidase system in the livers of senescent rats is characterized by: (1) a reduced cytochrome P-450 content; (2) a decline in the specific activity of NADPH-cytochrome c (P-450) reductase; and (3) a slower rate of ethylmorphine N-demethylation in comparison to young adult animals. Since several factors intrinsic to the microsomes may influence the efficacy of the mixed function oxidase system, e.g. the phospholipid and cholesterol contents, the saturation index of the fatty acids and the fluidity of the membranes, we conducted a physicochemical analysis of liver microsomes isolated from young adult (3-4 months), mature (12-16 months) and senescent (25-27 months) male Fischer rats. Although the microsomal cholesterol content did not change appreciably between maturity and senescence, there was a marked decline in the total phospholipid content. This resulted in a significant increase in the cholesterol/phospholipid ratio, 0.49 to 0.65 between 16 and 27 months of age. The age-related changes in the total phospholipid content were largely reflected in each of the major fractions, i.e. phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine + phosphatidylserine. Small increases in the relative percentages of highly unsaturated fatty acid species were offset by similar decreases in the more frequent and more saturated species as a function of increased age. As a result, the net change in the fatty acid saturation index was probably minimal. However, the increase in the cholesterol/phospholipid ratio most likely contributes to the significant decline in the order parameter of microsomes isolated from old rats which, in turn, may impair the functional capacity of the hepatic mixed function oxidase system.     

Effect of acute and repeated chlordimeform treatment on rat hepatic microsomal drug metabolizing enzymes

The effect of chlordimeform treatment on the hepatic microsomal drug metabolizing enzymes was examined in male and female rats following either acute or repeated treatment. After acute administration of chlordimeform (100 mg/kg, ip one hr prior to sacrifice) differential effects were observed in various parameters of the hepatic microsomal mixed function oxidase system with significant decreases in ethylmorphine metabolism, cytochrome P-450 content, NADPH cytochrome c reductase, and in the spectral binding of hexobarbital and aniline while no changes were found in the metabolism of aniline or p-nitroanisole. Durations of zoxazolamine-induced paralysis and pentobarbital-induced hypnosis were increased significantly after acute chlordimeform administration. Following repeated administration of chlordimeform (75 mg/kg ip for four days) to adult male rats, a decrease was observed in zoxazolamine-induced paralysis time while pentobarbital-induced hypnosis was not altered. Metabolism studies using isolated hepatic microsomal fractions showed a decrease rate of biotransformation of ethylmorphine and aniline while the activity of p-nitroanisole O-demethylase was not changed. No differences were found in cytochrome P-450 levels whereas microsomal spectral binding of hexobarbital was reduced while that of aniline was not affected. Following acute or repeated administration of chlordimeform to adult female rats, decreases in the hepatic microsomal metabolism of aniline, but not ethylmorphine or p-nitroanisole, were observed. Addition of chlordimeform to microsomal suspensions yielded a Type I spectral binding curve.     

Effect of oxygen limitation on the content of n-hexadecane-inducible cytochrome P-450 in Acinetobacter calcoaceticus strain EB 104

The content of cytochrome P-450 as a function of oxygen supply was studied during growth of Acinetobacter on n-hexadecane in batch cultures at constant pH and agitation. The rate of growth and the content of cytochrome P-450 were not affected as long as the dissolved oxygen tension ranged above 3 to 5% of saturation. The amount of cytochrome P-450 increased when the oxygen tension declined to zero. Cytochrome P-450 levels of about 0.3 to 0.4 nmol/mg protein, i.e. a more than a threefold increase, were observed under conditions where oxygen supply was strictly limited and allowed to maintain only a minimum of metabolism or growth. Limited oxygen supply exerted a special effect on the induction of the cytochrome P-450 as concluded from an increasing ratio between cytochrome P-450 and cytochrome o, and from the absence of cytochrome d in cells with elevated content of cytochrome P-450. The increased formation of cytochrome P-450 was a reversible process.