Bioactivation of cysteine conjugates of 1-nitropyrene oxides by cysteine conjugate beta-lyase purified from Peptostreptococcus magnus.

To determine the role of cysteine conjugate beta-lyase (beta-lyase) in the metabolism of mutagenic nitropolycyclic aromatic hydrocarbons, we determined the effect of beta-lyase on the mutagenicities and DNA binding of cysteine conjugates of 4,5-epoxy-4,5-dihydro-1-nitropyrene (1-NP 4,5-oxide) and 9,10-epoxy-9,10-dihydro-1-nitropyrene (1-NP 9,10-oxide), which are detoxified metabolites of the mutagenic compound 1-nitropyrene. We purified beta-lyase from Peptostreptococcus magnus GAI0663, since P. magnus is one of the constituents of the intestinal microflora and exhibits high levels of degrading activity with cysteine conjugates of 1-nitropyrene oxides (1-NP oxide-Cys). The activity of purified beta-lyase was optimal at pH 7.5 to 8.0, was completely inhibited by aminooxyacetic acid and hydroxylamine, and was eliminated by heating the enzyme at 55 degrees C for 5 min. The molecular weight of beta-lyase was 150,000, as determined by fast protein liquid chromatography. S-Arylcysteine conjugates were good substrates for this enzyme. As determined by the Salmonella mutagenicity test, 5 ng of beta-lyase protein increased the mutagenicity of the cysteine conjugate of 1-NP 9,10-oxide (10 nmol per plate) 4.5-fold in Salmonella typhimurium TA98 and 4.1-fold in strain TA100. However, beta-lyase had little effect on the cysteine conjugate of 1-NP 4,5-oxide (10 nmol per plate). Both conjugates exhibited only low levels of mutagenicity with nitroreductase-deficient strain TA98NR. In vitro binding of 1-NP oxide-Cys to calf thymus DNA was increased by adding purified beta-lyase or xanthine oxidase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of biotransformation enzymes by the carcinogenic air-pollutant 3-nitrobenzanthrone in liver, kidney and lung, after intra-tracheal instillation in rats

We investigated the effect of the seasonal variability of environmental air pollutants on oxidative stress and cytogenetic biomarkers in a group of 59 city policemen working in Prague, Czech Republic. The studied group was monitored in February and May 2007. The exposure to environmental pollutants (carcinogenic polycyclic aromatic hydrocarbons, c-PAHs, including benzo[a]pyrene, B[a]P, and particulate matter of aerodynamic diameter<2.5μm, PM2.5) was measured by personal and/or stationary monitors. Levels of c-PAHs were significantly higher in winter than spring, while exposure to PM2.5 was higher in May than in February 2007. We did not observe any significant difference between the two seasons for any biomarker of oxidative stress (8-oxo-7,8-dihydro-2'-deoxyguanosine, 8-oxodG, 15-F(2t)-isoprostane, 15-F(2t)-IsoP, protein carbonyl levels) or any cytogenetic parameter, including the genomic frequency of translocations (F(G)/100), the percentage of aberrant cells (%AB.C.) or the number of acentric fragments (ace). Analyses of associations between oxidative stress biomarkers and cytogenetic parameters showed a negative relationship between protein oxidation and F(G)/100, as well as protein oxidation and ace. We further analyzed the effect of air pollution on all subjects regardless of the season. Data from stationary monitors showed that 8-oxodG levels were significantly increased by exposure to PM2.5 over a 2-day period before sampling and by exposure to B[a]P over a 28-day period, days 57-84 before sampling. 15-F(2t)-IsoP levels were increased after exposure to B[a]P over both 2-day and 3-day periods preceding sample collection and after exposure to c-PAHs over a 2-day period before sampling. %AB.C. was significantly affected by exposure to B[a]P over a 14-day period, days 57-70 before sampling. In summary, our results indicate that the exposure to environmental pollutants affects urinary excretion of 8-oxodG, lipid peroxidation and the frequency of chromosomal aberrations.     

Formation of reactive 1-nitropyrene metabolites by lung microsomes and isolated lung cells

The metabolism and activation of 1-nitropyrene (1-NP) to reactive intermediates by lung microsomes and isolated lung cells was studied. Mutagenicity of 1-NP metabolites was assayed in Salmonella typhimurium TA98NR, a strain lacking a major component of nitroreductase activity. In the presence of NADPH, microsomes from rabbit, rat and hamster lung metabolized 1-NP to mutagenic products to a similar degree. Pretreatment with a mixture of polychlorinated biphenyls (PCB) decreased the formation of mutagenic metabolites by rabbit lung microsomes, but did not affect the production of mutagens by rat or hamster lung microsomes. ³H-1-NP was metabolized to covalently bound protein products at a rate of 82 and 10 pmol/mg by rabbit and hamster lung microsomes, respectively, whereas no binding was detected in rat lung microsomes. PCB-pretreatment increased covalent protein binding of ³ H-1-NP in lung microsomes from hamster and rat, but decreased the binding in rabbit lung microsomes. High performance liquid chromatography analysis indicated that ³H-1-NP was readily converted to ring-hydroxylated products by rabbit and hamster lung microsomes; the rate was much lower with rat lung microsomes. ³H-1-NP was activated to metabolites that covalently bound to protein in isolated rabbit lung cells, with the following rates being observed: Clara cells > lung digest > type II cells. In contrast, covalent protein binding in cells isolated from rat lung was very low. 1-NP was not activated to products mutagenic for S. typhimurium TA 98 N R when co-incubated with cells isolated either from rabbit or rat lung.Abbreviations 1-AP 1-aminopyrene - DMSO dimethyl sulfoxide - EGTA ethylene glycol-bis(ß-aminoethyl ether) - EM electron microscopy - HEPES N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid - HPBS HEPES-phosphate-buffered-saline - HPLC high performance liquid chromatography - NBT nitroblue tetrazolium - 1-NP 1-nitropyrene - 1-NP-4,5-diol trans-4,5-dihydro-4,5-dihydroxy-1-nitropyrene - 1-NP-9,10-diol trans-9,10-dihydro-9,10-dihydroxy-1-nitropyrene - 1-NP-4,5-oxide 1-nitropyrene-4,5-oxide - 1-NP-9,10-oxide 1-nitropyrene-9,10-oxide - 3-OH-1-NP 3-hydroxy-1-nitropyrene - 6-/8-OH-1-NP a mixture of 6- and 8-hydroxy-1-nitropyrene - PBS phosphate-buffered saline - PCB a mixture of polychlorinated biphenyls (Aroclor 1254) - TLC thin layer chromatography     

Bioactivation of diesel exhaust particle extracts and their major nitrated polycyclic aromatic hydrocarbon components, 1-nitropyrene and dinitropyrenes, by human cytochromes P450 1A1, 1A2, and 1B1

The genotoxicities of four samples of diesel exhaust particle (DEP) extracts (DEPE) and nine nitroarenes found in DEPE were investigated after activation catalyzed by human cytochrome P450 (P450) family 1 enzymes co-expressed with NADPH-cytochrome P450 reductase (NPR) in Escherichia coli membranes. The DEPE samples induced umu gene expression in Salmonella typhimurium TA1535/pSK1002 without any P450 system and were further activated by human P450 1B1/NPR membranes. Moderate activation of the DEPE sample by P450 1A2/NPR membranes was also observed, but not by either P450 1A1/NPR or NPR membranes. 1-Nitropyrene (1-NP) was strongly activated by human P450 1B1/NPR membranes. 1,8-Dinitropyrene (1,8-DNP) was most highly activated by P450 1A1 and 1B1 systems for the three DNPs tested. In contrast, 1, 3-DNP was inactivated by P450 1A1/NPR, 1A2/NPR, and 1B1/NPR systems and slightly activated by NPR membranes. 2-Nitrofluoranthene (2-NF) and 3-nitrofluoranthene (3-NF) showed activities similar to 1-NP after bioactivation by P450 1B1/NPR membranes. However, the genotoxicities of 6-nitrochrysene, 7-nitrobenz[a]anthracene, and 6-nitrobenzo[a]pyrene were all weak in the present assay system. Apparent genotoxic activities of DEPE were very low compared with standard nitroarenes in the presence of P450s, possibly because unknown component(s) of DEPE had inhibitory effects on the bioactivation of 1-NP and 1,8-DNP catalyzed by human P450 1B1. These results suggest that environmental chemicals existing in airborne DEP, in addition to 1-NP, 1,6-DNP, 1,8-DNP, 2-NF, and 3-NF, can be activated by human P450 1B1. Biological actions of air pollutants such as nitroarenes to human extrahepatic tissues may be of concern in tissues in which P450 1B1 is expressed.     

Bioactivation of diesel exhaust particle extracts and their major nitrated polycyclic aromatic hydrocarbon components, 1-nitropyrene and dinitropyrenes, by human cytochromes P450 1A1, 1A2, and 1B1

The genotoxicities of four samples of diesel exhaust particle (DEP) extracts (DEPE) and nine nitroarenes found in DEPE were investigated after activation catalyzed by human cytochrome P450 (P450) family 1 enzymes co-expressed with NADPH-cytochrome P450 reductase (NPR) in Escherichia coli membranes. The DEPE samples induced umu gene expression in Salmonella typhimurium TA1535/pSK1002 without any P450 system and were further activated by human P450 1B1/NPR membranes. Moderate activation of the DEPE sample by P450 1A2/NPR membranes was also observed, but not by either P450 1A1/NPR or NPR membranes. 1-Nitropyrene (1-NP) was strongly activated by human P450 1B1/NPR membranes. 1,8-Dinitropyrene (1,8-DNP) was most highly activated by P450 1A1 and 1B1 systems for the three DNPs tested. In contrast, 1,3-DNP was inactivated by P450 1A1/NPR, 1A2/NPR, and 1B1/NPR systems and slightly activated by NPR membranes. 2-Nitrofluoranthene (2-NF) and 3-nitrofluoranthene (3-NF) showed activities similar to 1-NP after bioactivation by P450 1B1/NPR membranes. However, the genotoxicities of 6-nitrochrysene, 7-nitrobenz[a]anthracene, and 6-nitrobenzo[a]pyrene were all weak in the present assay system. Apparent genotoxic activities of DEPE were very low compared with standard nitroarenes in the presence of P450s, possibly because unknown component(s) of DEPE had inhibitory effects on the bioactivation of 1-NP and 1,8-DNP catalyzed by human P450 1B1. These results suggest that environmental chemicals existing in airborne DEP, in addition to 1-NP, 1,6-DNP, 1,8-DNP, 2-NF, and 3-NF, can be activated by human P450 1B1. Biological actions of air pollutants such as nitroarenes to human extrahepatic tissues may be of concern in tissues in which P450 1B1 is expressed.     

Biodegradation of 1-nitropyrene

The metabolism of ¹⁴C-labeled 1-nitropyrene in microcosms containing nonsterile estuarine sediments, and in cultures of a Mycobacterium sp. previously isolated from oil-contaminated sediments was investigated. Although mineralization of 1-nitropyrene by pure cultures of the Mycobacterium sp. totaled only 12.3% after 10 days of incubation, over 80% of the ethyl acetate extractable ¹⁴C-labeled compounds consisted of 1-nitropyrene metabolites. High pressure liquid chromatographic analysis of 1-nitropyrene degradation products indicated that two major metabolites were formed. They were identified as 1-nitropyrene cis-9,10-and 4,5-dihydrodiols, based on their UV-visible, mass and NMR spectra. Time course studies in microcosms showed that 1-nitropyrene was degraded slowly under aerobic and anaerobic conditions in estuarine sediments. Less than 1% had been converted to ¹⁴CO₂ after 8 weeks of aerobic incubation. The addition of 1-nitropyrene to anaerobic sediments resulted in no ¹⁴CO₂ evolution; however, the nitro group of 1-nitropyrene was reduced to form 1-aminopyrene. Although the mineralization of 1-nitropyrene in sediments was slow, the Mycobacterium sp. metabolized 1-nitropyrene in pure culture. This bacterium appears promising for the bioremediation of this ubiquitous pollutant in contaminated waste.Abbreviations DEP Direct exposure probe - HPLC high pressure liquid chromatography - GC/MS gas chromatography/mass spectrometry - Nitro-PAHS nitropolycyclic aromatic hydrocarbons - TLC thin-layer chromatography - UV ultraviolet     

Toxicity and DNA damage induced by 1-nitropyrene and its derivatives in Chinese hamster lung fibroblasts

1-Nitropyrene and its chemically synthesised derivatives were investigated for their cytotoxicity and ability to induce DNA-strand breaks in Chinese hamster lung fibroblasts. Both 1-nitrosopyrene (0.25-60 micrograms/ml) and 1-aminopyrene (0.25-25 micrograms/ml) were cytotoxic, and induced the formation of DNA lesions, which were measured as DNA single-strand breaks after sedimentation in alkaline sucrose-density gradients. Higher doses of 1-aminopyrene (25-60 micrograms/ml) inhibited the formation of DNA single-strand breaks. 1-Nitropyrene was not toxic (0.25-60 micrograms/ml) and induced low levels of detectable DNA strand breaks, whilst N-acetyl-1-aminopyrene was inactive. The post-mitochondrial supernatant fraction of Aroclor-induced rat-liver containing 4 mM NADPH (S9 mix) did not promote the activation of 1-nitropyrene. In fact DNA strand breaks induced by either 1-nitropyrene or 1-nitrosopyrene was abolished in the presence of S9 mix. The 1-nitropyrene reduced intermediate, N-hydroxy-1-aminopyrene was synthesised by the reduction of 1-nitrosopyrene with ascorbic acid. In the presence of ascorbic acid, 1-nitrosopyrene caused a 5-fold increase in the number of DNA single-strand breaks when compared to cells treated with 1-nitrosopyrene alone. The results are discussed in terms of the metabolic activation of 1-nitropyrene and 1-aminopyrene in Chinese hamster lung cells.     

Cannabis 25 1, biotransformation of cannabidiol and cannabidiolic acid by Pinellia ternata tissue segments

Two marihuana constituents, cannabidiol (1) and cannabidiolic acid (4) were each converted mainly to two metabolites using tissue segments of Pinellia ternata tuber. The structures of the metabolites formed from 1 were determined to be 1-O-D-glucopyranoside and 1-O-D-diglucopyranoside by ¹H nmr, ¹³C nmr and fabms. Those from 4 were determined as 4-O-D-glucopyranoside and 10-hydroxyl 4-O-D-glucopyranoside. In time course experiments, 1 was absorbed rapidly by the tissues and glucosylated. Hydroxylation subsequent to the glucosylation occurred at the pentyl group in 4.1 For Part 24, see Taura F, Morimoto S, Shoyama Y, Mechoulam R (1995) J Am Chem Soc 117:9766–9767     

Brown adipose tissue, liver, and diet-induced thermogenesis in cafeteria diet-fed rats

Diet-induced thermogenesis (DIT) in young rats overeating a "cafeteria" (CAF) diet of palatable human foods is characterized by a chronic, propranolol-inhibitable elevation in resting metabolic rate (VO2) and is associated with various changes in brown adipose tissue (BAT) that have been taken as evidence for BAT as the effector of DIT. But direct evidence for participation of BAT in DIT has been lacking. By employing a nonocclusive cannula to sample the venous effluent of interscapular BAT (IBAT) for analysis of its O2 content and measuring tissue blood flow with microspheres, we accomplished direct determination (Fick principle) of the O2 consumption of BAT in conscious CAF rats. In comparison with normophagic controls fed chow, the CAF rats exhibited a 43% increase in metabolizable energy intake, reduced food efficiency, a 22% elevation in resting VO2 at 28 degrees C (thermoneutrality) or 24 degrees C (housing temperature), and characteristic changes in the properties of their BAT (e.g., increased mass, protein content and mitochondrial GDP binding). They also exhibited the greater metabolic response to exogenous noradrenaline characteristic of CAF rats and the near elimination by propranolol of their elevation in VO2. By the criterion of their elevated VO2, the CAF rats were exhibiting DIT at the time of the measurements of BAT blood flow and blood O2 levels. However, BAT O2 consumption was found to be no greater in the CAF rats than in the controls at either 28 or 24 degrees C. At 28 degrees C it accounted for less than 1% of whole body VO2; at 24 degrees C it increased to about 10% of overall VO2 in both diet groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pyridine nucleotides in lung and liver of hypoxic rats

Adult male albino rats of Wistar strain in the weight range of 170–200 g were exposed to acute hypobaric hypoxia of 25,000 ft at 32°C for 90, 180, 270 and 360 min. respectively. The extramitochondrial dehydrogenases generating NADPH and the mitochondrial dehydrogenases generating NADH were studied in lung and liver. The oxidized and the reduced forms of these two nucleotides were determined at 90 min. and 360 min. of hypoxia. Hypoxia caused an initial decline in the activities of all the dehydrogenases studied. The activities of mitochondrial and pentose phosphate dehydrogenases of liver were high at 360 min. of hypoxia whereas the activities of extramitochondrial dehydrogenases of lung were generally low at all levels of hypoxic exposure. The NADPH levels of hypoxic rat lung were correspondingly low. However, the activities of liver mitochondrial dehydrogenases were elevated at 360 min. of hypoxia in spite of NADH accumulation in hypoxic rat liver. A decreased NAD/NADH ratio was observed in lung at 90 min. and 360 min. of hypoxia.     

Biological fate of [14C]-1-nitropyrene in rats following intragastric administration

1-Nitropyrene (1-NP), a weak carcinogen associated with diesel exhaust particles, has previously been detected in workplace atmospheres with in-use diesel engines and in the general environment. In order to gain insight in its biological fate, a single dose of [14C]-1-NP (27.6 microCi, 750 mg/kg body weight, b.w.) was administered intragastrically to rats and the presence of metabolites in blood and tissue homogenates, and radioactivity associated with blood proteins and tissue DNA, were studied. Early peak levels of radioactivity observed in blood and tissue homogenates indicated a rapid absorption of [14C]-1-NP from the gastrointestinal tract. Metabolite patterns observed in plasma, liver and kidney homogenates strongly suggested an important role of the intestinal microflora in the enterohepatic recirculation, but not in nitroreduction of 1-NP prior to absorption from the gastrointestinal tract. This might explain the low levels of radioactivity associated with blood proteins, since 1-nitrosopyrene, a product of nitroreduction of 1-NP, is likely to be involved in protein binding. Levels of radioactivity associated with plasma proteins were approximately four times higher than the levels of radioactivity associated with hemoglobin (401.0 and 84.1 pmol/g protein per micromol 1-NP kg b.w., respectively, at 24 h). Maximal 25% of the associated radioactivity was released following mild alkaline hydrolysis of either hemoglobin or plasma proteins. 1-Aminopyrene was the only released compound after hydrolysis of hemoglobin. In addition to 1-aminopyrene, two more polar unidentified metabolites were detected following hydrolysis of plasma proteins. Association of radioactivity with DNA was highest in the liver at the first moments of observation (7.4 pmol 14C Eq./mg DNA per micromol 1-NP kg b.w.), but decreased rapidly to levels lower than observed for kidney DNA (max. 3.0 pmol 14C Eq./mg DNA per micromol 1-NP kg b.w. at 24 h). In lungs 8-50 times less radioactivity was associated with DNA than observed in the liver and kidneys. The results of this study show, that 1-NP undergoes an extensive and complex biotransformation in vivo, resulting in a variety of metabolites present in blood and tissue homogenates and a diversity of blood protein adducts. Concentrations of plasma metabolites, blood protein adducts and DNA adducts were rather low. In addition, previous studies also showed relatively low concentrations of metabolites present in urine. Therefore, sensitive and selective methods will be needed in order to evaluate the biological fate of 1-NP, associated with diesel exhaust particles, in humans.     

Clastogenicity of 1-nitropyrene, dinitropyrenes, fluorene and mononitrofluorenes in cultured Chinese hamster cells

The chromosomal aberration test using a Chinese hamster lung cell line (CHL) was carried out on 1-nitropyrene (NP), 3 dinitropyrenes (DNPs), fluorene and 4 mononitrofluorenes with and without metabolic activation (rat S9 mix). The 3 DNPs (1,3-, 1,6- and 1,8-DNP) induced chromosomal aberrations in the absence of S9 mix. The frequencies of cells with aberrations after treatment for 48 h were 43% at 2 micrograms/ml of 1,3-DNP, 55% at 0.1 microgram/ml of 1,6-DNP and 45% at 0.025 microgram/ml of 1,8-DNP, indicating the order of clastogenic potency as 1,8- greater than 1,6- greater than 1,3-DNP. On the other hand, 1-NP, which is known to be a direct-acting mutagen in bacteria, was negative in the chromosomal aberration test without S9 mix, but clearly positive with S9 mix. This effect was dependent on the concentration of the S9 fraction in the reaction mixture. High-pressure liquid chromatography analysis showed that 1-NP was converted by S9 mix to several metabolites, including 1-aminopyrene (AP). The clastogenic activity of 1-AP, however, was equivocal without S9 mix, suggesting that active clastogens other than 1-AP exist. Fluorene induced chromosomal aberrations only in the presence of S9 mix (61.8% at 25 micrograms/ml). 1-, 2-, 3- and 4-nitrofluorene (NF) were more clastogenic in the presence of S9 mix than in the absence of S9 mix, suggesting that NFs were converted to more active clastogens by S9 mix.     

DNA damage in stomach, kidney, liver and lung of rats treated with atrazine

The genotoxic activity of atrazine, a widely used triazine herbicide, was assayed by the DNA alkaline elution technique in rats given orally a single high dose or repeated daily doses. DNA breaks (and/or alkali-labile lesions) were detected in cell suspensions obtained from stomach, kidney and liver, but not in those from lung.     

Mutation spectra induced by 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide in the supF gene of human XP-A fibroblasts

1-Nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide are oxidative metabolites that are responsible for the mutagenicity of 1-nitropyrene. In this study, the mutation spectra induced by oxidative metabolites in human cells were determined using a shuttle vector assay. The mutation frequencies induced by 1-nitropyrene 9,10-oxide were 2-3 times higher than those induced by 1-nitropyrene 4,5-oxide. The base substitutions induced by 1-nitropyrene 4,5-oxide were G --> A transitions, G --> C transversions, and G --> T transversions. In the case of 1-nitropyrene 9,10-oxide, G --> A transitions, G --> T transversions, A --> G transitions and G --> C transversions were observed. Most base substitution mutations induced by oxidative metabolites occurred at the guanine sites in the supF gene. These sequence-specific hot spots were commonly identified as 5'-GA sequences for both metabolites. On the other hand, the sequence-specific hot spots at the adenine sites were identified as 5'-CAC sequences for 1-nitropyrene 9,10-oxide. These results suggest that the oxidative metabolites of 1-nitropyrene induce sequence-specific DNA mutations at the guanine and adenine sites at high frequency.     

Mutagenicity of derivatives and metabolites of 1-nitropyrene: activation by rat liver S9 and bacterial enzymes

The mutagenicity and activation requirements of purified synthetic derivatives and potential metabolites of 1-nitropyrene have been characterized in the Ames plate incorporation assay with the Salmonella tester strains TA98, TA98NR and TA98/1,8-DNP6, in the presence or absence of exogenous metabolic activation provided by Aroclor-induced rat liver S9. All the compounds tested (1-aminopyrene, N-acetyl-1-aminopyrene, N-hydroxy-N-acetyl-1-aminopyrene, 3-hydroxy-1-nitropyrene, 6-hydroxy-1-nitropyrene, and 8-hydroxy-1-nitropyrene) exhibited mutagenic activity under one or more assay conditions. 1-Nitropyrene was metabolized to 3-hydroxy-1-nitropyrene, 6- or 8-hydroxy-1-nitropyrene, 1-aminopyrene, N-acetyl-1-aminopyrene and other unidentified products (including some bound to protein) by an S9 preparation analogous to that used for exogenous metabolic activation in the Ames assay. 1-Nitropyrene and 3-hydroxy-1-nitropyrene were activated primarily by the 'classical' nitroreductase, while the other compounds, particularly in the presence of S9 metabolic activation, were dependent on transesterification for expression of their mutagenicity.     

Adipose, muscle and lung tissue lipoprotein lipase activities in young streptozotocin treated rats

Lipoprotein lipase (LPL) activity was studied in adipose, muscle and lung tissues of post-weanling rats 48 and 96 hours after experimentally induced diabetes by streptozotocin administration. Weight gain was reduced, and blood glucose level increased about 3-4 fold above the control level as an indication of the diabetic state. LPL activity in brown and white adipose tissues decreased in diabetic rats to 10-30% of the control level. In soleus muscle the LPL activity was slightly enhanced 96 hours after the streptozotocin injection. In cardiac muscle the LPL activity was markedly increased already 48 hours after the administration of streptozotocin and the increase remained significant until 96 hours. There was in the pulmonary tissue also an increase of LPL activity of diabetic rats, although this was significant only 96 hours after streptozotocin treatment. The results suggest marked tissue specific variation in the LPL activity. Moreover, tissue responses to experimentally induced diabetes vary. In adipose tissue the decrease in the LPL activity suggests that lipid transport to adipocytes is decreased while an increase in skeletal and cardiac muscles and in lung tissue proposes that their lipid utilization is enhanced.     

The 1-nitropyrene reductase of Salmonella typhimurium

We have devised a sensitive fluorimetric assay to monitor the conversion of 1-nitropyrene to 1-aminopyrene. Application of this assay to extracts of Salmonella typhimurium strains TA98 and TA100 (which are sensitive to the mutagenic and lethal effects of 1-nitropyrene) has shown that these bacteria contain 'nitropyrene reductase' activity at the low level of 10(-11) mol/min/mg protein. NADPH and NADH serve equally well as reducing agents. The nitropyrene reductase activity of strain TA100 F50 (a mutant resistant to 1-nitropyrene) was found to be considerably lower.