芳香烃羟化酶活性与苯并[a]芘中间代谢产物生成关系的研究

100mg香烟烟油,多氯联苯诱导大鼠肝S_9组分中芳香烃羟化酶代谢B[a]P为3-OH-B[a]P的活性分别升高约40,20倍,而代谢B[a] P生成6-OXY-B [a]P自由基产物却仅由多氯联苯诱导的S_9组分作用中才被观察到。     

Time course of the induction of aryl hydrocarbon hydroxylase in rat liver nuclei and microsomes by phenobarbital, 3-methylcholanthrene, 2,3,7,8-tetrachloro-dibenzo-p-dioxin,dieldrin and other inducers

Aryl hydrocarbon hydroxylase (AHH) has been measured in male rat liver nuclei and microsomes after treatment of adult animals with various inducers for up to 14 days. After daily i.p. injections of 3-methylcholanthrene (MC, 20 mg/kg) the nuclear activity increased to a maximum of 600 per cent of the control activity after 4 days whereas the microsomal activity was 400 per cent of control at the same date. After 12 days, both activities equilibrated at 400 per cent. A similar time course was found after a single i.p. injection of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD, 0.01 mg/kg) with an induction to 500 and 300 per cent for nuclei and microsomes, respectively, after 2 days, and to 400 per cent for both after 12 days. Phenobarbital (PB) was given continuously in the drinking water (1 g/l) and induced the microsomal activity to 200 per cent after 8 days and 170 per cent after 14 days. the nuclear activity was only slightly induced to a Constant level of 130 per cent between day 8 and 14. Dieldrin did not significantly increase the microsomal activity after daily i.p. injections (20 mg/kg), but the nuclear activity raised to 200 per cent after 3 days and levelled down to control values after 12 days. Other inducers tested were benz[a]anthracene (BA), hexachlorobenzene (HCB) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT). The induction pattern with BA was similar to that of MC, a model compound for the group of cytochrome P448 inducers. the induction by HCB and DDT resembled that by PB, a typical cytochrome P450 inducer.     

Epidermal cell growth-dependent arylhydrocarbon-hydroxylase (AHH) activity in vitro

Summary Cytochrome P-450-dependent arylhydrocarbon-hydroxylase (AHH) activity and inducibility by benzanthracene (BA) was measured in cultured guinea pig and human epidermal cells. Basal AHH-activity (AHH_b) in guinea pig epidermal cells was much higher than in human epidermal cells. AHH_b in guinea pig epidermal cells was directly related to the labeling index and decreased to the original level between the 5th and 7th day of cell culturing. On the other hand, the induction-ratio of AHH reached its maximum level when the number of cells began to rise (proliferation phase) and remained high at day 7 of the cell culture. These results suggest a cell growth dependent activity and inducibility of carcinogen-metabolizing enzymes, such as AHH, in isolated epidermal cells.Dedicated to Prof. Dr. Dr. h.c. Otto Braun-Falco on the occasion of his 65th birthday     

Effect of dietary vitamin E on nitrite-treated rats

The effect of dietary vitamin E on cellular responses to nitrite was studied in rats. One-month-old male Sprague-Dawley rats were fed a basal vitamin E-deficient diet with or without 100 ppm vitamin E and 1000 ppm sodium nitrite (NaNO₂) for 9 weeks. In addition to a high mortality rate, nitrite-fed rats maintained on a vitamin E-deficient diet exhibited a marked increase in liver necrosis, tubular nephrosis and myodegeneration, as well as greater biochemical and hematological alterations when compared to the control animals. No animal mortality or histopathologic lesions in any tissues were observed in rats receiving a vitamin E-supplemented diet with or without nitrite. The results suggest that depletion of vitamin E renders rats more susceptible to the adverse effect of nitrite, and that nitrite administration potentiates deficiency of vitamin E in rats.     

Monoclonal antibodies to phenobarbital-induced rat liver cytochrome P-450

Somatic cell hybrids were made between mouse myeloma cells and spleen cells derived from BALB/c female mice immunized with purified phenobarbital-induced rat liver cytochrome P-450 (PB-P-450). Hybridomas were selected in HAT medium, and the monoclonal antibodies (MAbs) produced were screened for binding to the PB-P-450 by radioimmunoassay, for immunoprecipitation of the PB-P-450, and for inhibition of PB-P-450-catalyzed enzyme activity. In two experiments, MAbs of the IgM and IgG1 were produced that bound and, in certain cases, precipitated PB-P-450. None of these MAbs, however, inhibited the PB-P-450-dependent aryl hydrocarbon hydroxylase (AHH) activity. In two other experiments, MAbs to PB-P-450 were produced that bound, precipitated and, in several cases, strongly or completely inhibited the AHH and 7-ethoxycoumarin deethylase (ECD) activities of PB-P-450. These MAbs showed no activity toward the purified 3-methylcholanthrene-induced cytochrome P-450 (MC-P-450), β-naphthoflavone-induced cytochrome P-450 (BNF-P-450) or pregnenolone 16-α-carbonitrile-induced cytochrome P-450 (PCN-P-450) in respect to RIA determined binding, immunoprecipitation, or inhibition of AHH activity. One of the monoclonal antibodies, MAb 2-66-3, inhibited the AHH activity of liver microsomes from PB-treated rats by 43% but did not inhibit the AHH activity of liver microsomes from control, BNF-, or MC-treated rats. The MAb 2-66-3 also inhibited ECD in microsomes from PB-treated rats by 22%. The MAb 2-66-3 showed high cross-reactivity for binding, immunoprecipitation and inhibition of enzyme activity of PB-induced cytochrome P-450 from rabbit liver (PB-P-450_LM2). Two other MAbs, 4-7-1 and 4-29-5, completely inhibited the AHH of the purified PB-P-450. MAbs to different cytochromes P-450 will be of extraordinary usefulness for a variety of studies including phenotyping of individuals, species, and tissues and for the genetic analysis of P-450s as well as for the direct assay, purification, and structure determination of various cytochromes P-450.     

Influence of pretreatment with tobacco smoke condensate or 3-methylcholanthrene on [14C] benzo (A) pyrene metabolism in the isolated perfused rabbit lung

Pretreatment 24 h before sacrifice with i.p. tobacco smoke condensate (TSC) or 3-methylcholanthrene (3MC) increased the rate of disappearance of [¹⁴C]benzo(a)pyrene (BP) from an isolated perfused rabbit lung model. Both pretreatments significantly increased the amount of most metabolites formed. This study indicates that rabbits tend to resemble rats, mice and hamsters in that increased rates of pulmonary BP metabolism are a consequence of exposure to TSC.     

Biological effects of the Sudan dyes. Role of the Ah cytosolic receptor

The hepatic induction of two cytochrome P1-450-mediated activities [aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (ETR)] was studied following the administration of the azo dyes Sudan I, II, III, and IV. When using Ah-responsive C57BL/6J mice, Sudan dye II proved to be quite potent as an inducer causing almost maximal induction at doses as low as 40 mg/kg (1.4 mumoles/kg body weight); Sudan dyes I, III and IV caused one-half the maximal induction at four times that dose. In contrast, none of these compounds caused induction of AHH or ETR in the Ah-nonresponsive DBA/2J animals. When the dyes were given to B6D2F1 X D2 backcross progeny, a strict correlation with the presence of the Ahb allele and the inducibility of AHH and ETR was observed. When these compounds were examined as agonists for the Ah cytosolic receptor by their capacity to replace [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin binding, Sudan dye II was substantially more effective than Sudan dyes I, III and IV. When four repeated doses of Sudan dye II were administered intraperitoneally to Ah-responsive C57BL/6J mice and Ah-nonresponsive DBA/2J mice, Sudan dye II-induced immunotoxicity was markedly greater in C57BL/6J compared to DBA/2J mice.     

Increased aryl hydrocarbon hydroxylase and prolyl hydroxylase activities in lung organ cultures exposed to benzo[a]pyrene

Exposure of neo-natal rat lungs in organ culture to 10–25 μM benzo[a]-pyrene (BaP) elevated the activities of aryl hydrocarbon hydroxylase (AHH) and prolyl hydroxylase (PH). Pyrene, a non-carcinogenic hydrocarbon did not elicit this response. Prolyl hydroxylase is an indicator of collagen synthesis and increased PH activity in the lungs reflects increased collagen synthesis. Our studies suggest that the earliest events in BaP-induced lung injury may include altered collagen metabolism.     

7-Ethoxycoumarin O-deethylase induction by phenobarbitone and 1,2-benzanthracene in primary maintenance cultures of adult rat hepatocytes

The microsomal monooxygenase system of adult rat hepatocytes in short-term non-proliferating culture could be induced by phenobarbitone and benzanthracene. Differences in the kinetics of induction and the additive nature of the inductions indicated that induction by the two agents occurred by different mechanisms and the use of haemoprotein-selective inhibitors demonstrated the induction of different haemoproteins by the two agents. The type of haemoprotein present in the cells altered during a four day culture period.