Reactivity with DNA bases and mutagenicity toward Salmonella typhimurium of methylchrysene diol epoxide enantiomers

The reactions with DNA and mutagenic activities toward Salmonella typhimurium TA 100 of the R,S,S,R and S,R,R,S enantiomers of anti-1,2,-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (anti-5-MeC-1,2-diol-3,4-epoxide), anti-5-MeC-7,8-diol-9,10-epoxide, and anti-6-MeC-1,2-diol-3,4-epoxide were compared because among these compounds only the R,S,S,R enantiomer of anti-5-MeC-1,2-diol-3,4-epoxide is highly tumorigenic. The major products formed in the reaction of each racemic diol epoxide with DNA were two pairs of deoxyguanosine (dGuo) and deoxyadenosine (dAdo) adducts; one product in each pair was formed from the R,S,S,R enantiomer and the other from the S,R,R,S enantiomer of each racemic diol epoxide. Formation of products from R,S,S,R enantiomers exceeded formation of those from S,R,R,S enantiomers in each case. Among the R,S,S,R enantiomers, 5-MeC-1,2-diol-3,4-epoxide, which has a methyl group in the same bay region as the epoxide ring, was most reactive toward DNA, and in particular toward dGuo. The dGuo/dAdo adduct ratios were greater for the products formed from the R,S,S,R enantiomer compared to the S,R,R,S enantiomer of each diol epoxide. The dGuo/dAdo adduct ratios were also greater for the enantiomers of anti-5-MeC-1,2-diol-3,4-epoxide than for the enantiomers of either anti-5-MeC-7,8-diol-9,10-epoxide or anti-6-MeC-1,2-diol-3,4-epoxide. In S. typhimurium TA 100, the R,S,S,R enantiomer of anti-5-MeC-1,2-diol-3,4-epoxide was the most mutagenic compound (6700 revertants/nmol), followed by the R,S,S,R enantiomer of anti-5-MeC-7,8-diol-9,10-epoxide (1500 revertants/nmol). The other diol epoxide enantiomers were weakly active or inactive at the doses tested. The results of this study demonstrate that both the absolute configuration of a diol epoxide and the position of the methyl group have major effects on its reactivity with DNA. The greatest reactivity is seen in an R,S,S,R enantiomer with the methyl group and epoxide ring in the same bay region, e.g., the highly tumorigenic and mutagenic 5-MeC-1R,2S-diol-3S,4R-epoxide. Comparison of the dGuo/dAdo adduct ratios of the various diol epoxides with their tumorigenic and mutagenic activities suggests that dGuo adducts are important in the expression of biological activity of methylchrysene diol epoxides.

Formation and tumorigenicity of benzo[b]fluoranthene metabolites in mouse epidermis

The metabolism in mouse epidermis of benzo[b]fluoranthene (BbF) was studied. [3H]BbF was applied topically, mice were killed at various intervals, and metabolites were extracted from the epidermis and analyzed by h.p.l.c. The major metabolites were identified by comparisons to standards as 4-, 5-, and 6-hydroxyBbF. Sulfate and glucuronide conjugates of these hydroxyBbF were also detected. Minor metabolites included 12-hydroxyBbF, BbF-1,2-diol, and BbF-11,12-diol. BbF-9,10-diol, the only known tumorigenic oxygenated derivative of BbF, was not detected. The further metabolism of BbF-9,10-diol was studied in vitro, using rat liver 9000 g supernatant. The major metabolites were identified by their spectral characteristics as 5- and 6-hydroxyBbF-9,10-diol. Little if any BbF-9,10,11,12-tetraol was detected. 5- and 6-HydroxyBbF-9,10-diol were not detected as metabolites of [3H]BbF in mouse epidermis. Several known and potential BbF metabolites--BbF-1,2-diol, BbF-11,12-diol, BbF-9,10-diol, BbF-9,10-diol-11,12-epoxide, 5- and 6-hydroxyBbF-9,10-diol, 1-hydroxyBbF, 5-hydroxyBbF, and 6-hydroxyBbF--were tested for tumor initiating activity on mouse skin. Among these, only BbF-9,10-diol showed high tumorigenic activity, but no evidence has been obtained for its formation in vivo from BbF. These studies do not support the hypothesis that BbF is metabolically activated through formation of the bay region diol epoxide, BbF-9,10-diol-11,12-epoxide.

Enhancing effect of a bay region methyl group on tumorigenicity in newborn mice and mouse skin of enantiomeric bay region diol epoxides formed stereoselectively from methylchrysenes in mouse epidermis

The stereochemistry of diol epoxide formation in mouse epidermis upon topical application of [3H]-1R,2R-dihydroxy-1,2-dihydro-5-methylchrysene ([3H]-5-MeC-1R,2R-diol) and [3H]-6-MeC-1R,2R-diol, and the tumorigenicity in mouse skin and in newborn mice of the R,S,S,R and S,R,R,S enantiomers of 1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (5-MeC-1,2-diol-3,4-epoxide), 5-MeC-7,8-diol-9,10-epoxide, and 6-MeC-1,2-diol-3,4-epoxide were examined. Analysis of tetraols and their derived tetraacetates present in mouse epidermis, 2 h after application of [3H]-5-MeC-1R,2R-diol or [3H]-6-MeC-1R,2R-diol, demonstrated greater than 90% stereoselectivity in formation of 5-MeC-1R,2S-diol-3S,4R-epoxide and 6-MeC-1R,2S-diol-3S,4R-epoxide. Taken together with previous data, these results demonstrate that there is a high degree of stereoselectivity for formation of R,S,S,R enantiomers of 5-MeC- and 6-MeC-1,2-diol-3,4-epoxides in mouse skin. The results of the tumorigenicity studies in mouse skin and in newborn mice clearly demonstrated that 5-MeC-1R,2S-diol-3S,4R-epoxide was the most tumorigenic of the diol epoxide enantiomers tested; 6-MeC-1R,2S-diol-3S,4R-epoxide was inactive. The results of this study show that the high tumorigenicity of 5-MeC compared to 6-MeC is due to the remarkable tumorigenic activity of 5-MeC-1R,2S-diol-3S,4R-epoxide which, in contrast to 6-MeC-1R,2S-diol-3S,4R-epoxide, has a methyl group in the same bay region as the epoxide ring. We propose that such methyl bay region diol epoxides of other carcinogenic methylated polynuclear aromatic hydrocarbons will also show unique tumorigenic properties.

High stereoselectivity in mouse skin metabolic activation of methylchrysenes to tumorigenic dihydrodiols

The stereoselectivity of mouse skin metabolic activation to dihydrodiols of the strong carcinogen 5-methylchrysene (5-MeC) and the weak carcinogen 6-methylchrysene (6-MeC) was investigated. Synthetic 1,2-dihydro-1,2-dihydroxy-5-methylchrysene (5-MeC-1,2-diol), 5-MeC-7,8-diol, and 6-MeC-1,2-diol were resolved into their R,R- and S,S-enantiomers by chiral stationary phase high performance liquid chromatography. The absolute configurations of the enantiomers were assigned by their circular dichroism spectra. Using these enantiomers as standards, the metabolism of 5-MeC and 6-MeC in vitro in rat and mouse liver and in vivo in mouse epidermis was investigated. Only the R,R-enantiomers of each dihydrodiol predominated (greater than 90%). The dihydrodiol enantiomers were tested for tumor initiating activity on mouse skin. In each case, the R,R-dihydrodiol enantiomer was significantly more tumorigenic than the S,S-enantiomer. The most tumorigenic compound was 5-MeC-1R,2R-diol; it was significantly more active than either 5-MeC-7R,8R-diol or 6-MeC-1R,2R-diol. The results of this study demonstrate that there is a high degree of stereoselectivity in the metabolic activation of 5-MeC and 6-MeC to proximate tumorigenic dihydrodiols in mouse skin. The bay region methyl group has no effect on the stereoselectivity of activation to 1,2-dihydrodiol metabolites in the chrysene system.

'Pseudo-lymphoid' leukaemia with unusual features: ultrastructural, immunological, cytogenetic and molecular studies

An unusual case of 'pseudo-lymphoid' leukaemia is described. The leukaemic cells resembled small, mature lymphocytes but lacked B- and T-cell membrane markers as well as immunoglobulin (Ig) and T-cell receptor gene rearrangements. They showed, instead, features of early myeloid cells since they expressed 2 myeloid antigens, CDW13 and My9, and displayed peroxidase activity demonstrable by electron microscopy (EM) on unfixed cells. Cytogenetic studies showed monosomy 5, t(4;17) (p12;p11), t(2;3)(p23;q14) and an abnormal chromosome 12. Abnormalities of chromosomes 4 and 5 have been previously associated with 'pseudo-lymphoid' leukaemias. This case illustrates the value of sensitive methods for the characterization of blast cells and for the precise diagnosis of leukaemias with apparent 'lymphoid' morphology.

Synthesis of 6-methylchrysene-1,2-diol-3,4-epoxides and comparison of their mutagenicity to 5-methylchrysene-1,2-diol-3,4-epoxides

The syn- and anti-isomers of 1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-6-methylchrysene (6-MeC-1,2-diol-3,4-epoxide) were synthesized and their mutagenic activities in Salmonella typhimurium were compared with those of the syn- and anti-isomers of 1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (5-MeC-1,2-diol-3,4-epoxide). The most mutagenic compound was anti-5-MeC-1,2-diol-3,4-epoxide, followed by syn-5-MeC-1,2-diol-3,4-epoxide. At the same doses, neither of the 6-MeC-1,2-diol-3,4-epoxides was mutagenic. These results demonstrate the enhancing effect on mutagenicity of a methyl group in the same bay region as the epoxide ring of a diol epoxide.

Effects of 6-nitro substitution on 5-methylchrysene tumorigenicity, mutagenicity and metabolism

6-Nitro-5-methylchrysene was prepared by nitration of 5-methylchrysene and the mutagenic and tumorigenic activities of the two compounds were compared. Whereas 5-methylchrysene was a strong tumor initiator on mouse skin, no tumors were observed in the mice treated with 6-nitro-5-methylchrysene. In Salmonella typhimurium TA100, both compounds were mutagenic in the presence, but not in the absence, of rat liver 9000 g supernatant. The major metabolite of 6-nitro-5-methylchrysene in rat liver in vitro was trans-1,2-dihydro-1,2-dihydroxy-6-nitro-5-methylchrysene. In view of the ready conversion of 6-nitro-5-methylchrysene to a 1,2-dihydrodiol, its apparent lack of tumorigenicity in mouse skin was intriguing.

Contrast, coagulation, and fibrinolysis

Some adverse clinical effects of intravascular radiologic contrast agents have been attributed to their interference with the normal hemostatic processes. This study compares the effects of the low osmolality agents with those of the conventional agents by in vitro studies of platelet function, fibrin formation, and fibrinolytic activation. In various degrees, all the contrast agents studied inhibit platelet aggregation and fibrin formation but show virtually no direct activation of fibrinolysis. The new low osmolality agents generally show lesser inhibitory effects on the hemostatic mechanisms. Some clinical implications are discussed.

Comparative metabolic activation in mouse skin of the weak carcinogen 6-methylchrysene and the strong carcinogen 5-methylchrysene

We compared the metabolic activation in mouse skin of the weak carcinogen 6-methylchrysene, which lacks a bay region methyl group, and the strong carcinogen 5-methylchrysene, which has a bay region methyl group. Metabolites of 6-methyl-chrysene were prepared using liver homogenates and were identified by their spectral properties and by comparison to synthetic standards as dihydrodiols, hydroxymethyl derivatives, and phenols; their relative levels of formation in liver homogenates from rats and mice were dependent on inducer pretreatment. In mouse skin in vivo, the major metabolite of 6-methyl-chrysene was trans-1,2-dihydro-1,2-dihydroxy-6-methylchrysene (6-MeC-1,2-diol), the precursor to a bay region dihydrodiol epoxide. Its concentration was greater than that of trans-1,2-dihydro-1,2-dihydroxy-5-methylchrysene (5-MeC-1,2-diol) formed in mouse skin from 5-methylchrysene. Since 5-MeC-1,2-diol has been identified as a major proximate carcinogen of 5-methylchrysene, the further metabolism and tumorigenicity of 5-MeC-1,2-diol and 6-MeC-1,2-diol were compared. Both dihydrodiols were converted to 1,2,3,4-tetraols and to 1,2-dihydroxy metabolites to similar extents in mouse skin. However, 5-MeC-1,2-diol was significantly more active than was 6-MeC-1,2-diol as a tumor initiator on mouse skin. The formation of DNA adducts in mouse skin from 5-methylchrysene and 6-methylchrysene was compared. Both hydrocarbons gave qualitatively similar adduct patterns, but the formation of dihydrodiol epoxide type adducts was 1/20 as great from 6-methylchrysene as from 5-methylchrysene. The results of this study indicate that the weak tumorigenicity of 6-methylchrysene compared to that of 5-methylchrysene is not due to differing rates of formation or further metabolism of their 1,2-dihydrodiols but is a likely consequence of the lower activity of 1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-6-methylchrysene compared to 1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene; the unique structural feature of the latter is the presence of a methyl group and an epoxide ring in the same bay region.

Mutagenicity and tumor initiating activity of methylated benzo[b]fluoranthenes

The mutagenicity toward S. typhimurium TA 100 and tumor initiating activity on mouse skin of benzo[b]fluoranthene (BbF), 1-methylbenzo[b]fluoranthene (1-MeBbF), 3-MeBbF, 7-MeBbF, 8-MeBbF, 9-MeBbF, 12-MeBbF, 5,6-dimethylbenzo[b]fluoranthene (5,6-diMeBbF) and 1,3-diMeBbF were assayed. Dose-dependent mutagenic activity was observed for BbF, 3-MeBbF, and 1,3-diMeBbF; the other compounds were inactive at the doses tested. 3-MeBbF and 1,3-diMeBbF were strong tumor initiators, with activity greater than that of BbF. All the other compounds were less tumorigenic than BbF. The results suggest that the structural features favoring tumorigenicity of methylated non-alternant polynuclear aromatic hydrocarbons such as BbF are different from those favoring tumorigenicity of methylated alternant polynuclear aromatic hydrocarbons such as benzo[a]pyrene, chrysene and benz[a]anthracene.

Rates of hydrolysis and extents of DNA binding of 5-methylchrysene dihydrodiol epoxides

The rates of hydrolysis in the absence and presence of native and denatured DNA, and the extents of DNA binding of five dihydrodiol epoxides derived from 5-methylchrysene (5-MeC) and chrysene have been determined. The compounds studied were: trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydro-5-MeC; trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydro-5-Mec; trans-1,2-dihydroxy-syn-3,4-epoxy-1,2,3,4-tetrahydro-5-MeC; trans-7,8-dihydroxy-syn-9,10-epoxy-7,8,9,10-tetrahydro-5-MeC; and trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydrochrysene. In the absence of DNA, at pH 7 and 37 degrees C half-lives of trans-1,2-dihydroxy-syn-3,4-epoxy-1,2,3,4-tetrahydro-5-MeC and trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydro-5-MeC were similar, t 1/2 = 62 and 59 min, while trans-7,8-dihydroxy-syn-9,10-epoxy-7,8,9,10-tetrahydro-5-MeC hydrolyzed faster than trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydro-5-MeC, t 1/2 = 5.4 versus 17.5 min; trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydrochrysene had the slowest rate of hydrolysis, t 1/2 = 104 min. Studies of the effects of native and denatured DNA on the rates of hydrolysis of the dihydrodiol epoxides indicated that native DNA remarkably accelerated these rates for all dihydrodiol epoxides, but the degree of acceleration varied for the different dihydrodiol epoxides. The acceleration of hydrolytic rates by native DNA relative to that by denatured DNA was correlated with the covalent binding of these dihydrodiol epoxides with DNA in vitro. The catalytic effect of DNA in enhancing the rates of hydrolysis of dihydrodiol epoxides and the relative extents of covalent binding of the dihydrodiol epoxides to DNA were in the following order: trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydro-5-MeC greater than trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydro-5-MeC greater than trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydrochrysene greater than trans-1,2-dihydroxy-syn-3,4-epoxy-1,2,3,4-tetrahydro-5-MeC greater than trans-7,8-dihydroxy-syn-9,10-epoxy-7,8,9,10-tetrahydro-5-MeC. The results of this study suggest that physical interactions with DNA are important in determining the relative extents of binding of these dihydrodiol epoxides to DNA in vitro.

Mutagenicity and tumor initiating activity of methylated benzo[k] fluoranthenes

The mutagenic activities toward Salmonella typhimurium TA100 and tumor initiating activities on mouse skin of the polynuclear aromatic hydrocarbons benzo[k]fluoranthene (BkF),2-methylBkF,8-methylBkF,9-methyl-BkF and 7,12-dimethylBkF were compared. BkF and 2-methylBkF were the most mutagenic of the compounds tested and had comparable activity; they were more active than 7,12-dimethylBkF. 8-MethylBkF and 9-methylBkF were not mutagenic. BkF and the methylated BkFs had similar tumor initiating activities on mouse skin. The results suggest that 8,9-dihydro-8,9-epoxy-BkF might be involved in the metabolic activation of BkF to a mutagen, but do not indicate which metabolite may be involved in BkF tumorigenesis.

Tumorigenicity of 5-methylchrysene dihydrodiols and dihydrodiol epoxides in newborn mice and on mouse skin

5-Methylchrysene, (+/-)-trans-1,2-dihydro-1,2-dihydroxy-5-methylchrysene, (+/-)-trans-7,8-dihydro-7,8-dihydroxy-5-methylchrysene, (+/-)-trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (anti-DE-I), (+/-)-trans-1,2-dihydroxy-syn-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (syn-DE-I), and (+/-)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydro-5-methylchrysene (anti-DE-II) were tested for tumorigenicity in newborn mice and for tumor-initiating activity on mouse skin. In newborn mice, a total dose of 56 nmol of anti-DE-I induced 4.6 lung tumors/mouse and 1.2 liver tumors/mouse. These incidences were significantly higher than observed for any of the other metabolites, tested at equimolar doses. The results indicate that anti-DE-I, but not syn-DE-I or anti-DE-II, is a major ultimate carcinogen of 5-methylchrysene in the newborn mouse. Anti-DE-I was also more tumorigenic than anti-DE-II on mouse skin, inducing 4.4 tumors/mouse after an initiating dose of 100 nmol, compared to zero tumors per mouse induced by anti-DE-II. However, anti-DE-I was less tumorigenic on mouse skin than was its metabolic precursor, trans-1,2-dihydro-1,2-dihydroxy-5-methylchrysene or its parent hydrocarbon, 5-methylchrysene.

The bay-region geometry of some 5-methylchrysenes: steric effects in 5,6- and 5,12-dimethylchrysenes

The presence of a bay-region methyl group in carcinogenic polycyclic aromatic hydrocarbons leads to considerable distortion in the molecule. This is illustrated in the structures, obtained by X-ray diffraction techniques, of 5,12- and 5,6-dimethylchrysene. The molecular distortions result from steric requirements, such as that the minimum H...H distance is 1.8 A and the minimum C...C distance is 2.90 A; distortions to accommodate these requirements may be both in-plane (by increasing the angles at carbon atoms in the bay-region from 120 degrees to approximately 124 degrees) and out-of-plane by torsion about certain bonds in the bay-region. It is shown that more in-plane distortions are found for 5-methylchrysene derivatives than for methylbenz[a]anthracene derivatives and this, it is suggested, results from the nature of the flexibility of the chrysene compared with the benz[a]anthracene fragment at the bay-region.

Inhibition by a peri-fluorine atom of 1,2-dihydrodiol formation as a basis for the lower tumorigenicity of 12-fluoro-5-methylchrysene than of 5-methylchrysene

12-Fluoro-5-methylchrysene, which has a fluorine atom at a peri position, is less carcinogenic toward mouse skin than is 5-methylchrysene. To determine the basis for this observation, we identified metabolites of 12-fluoro-5-methylchrysene formed by rat liver in vitro, and used these as standards to study the metabolism of [3H]-12-fluoro-5-methylchrysene in mouse liver in vitro and in mouse epidermis in vivo. Metabolites were identified by their ultraviolet, mass, and nuclear magnetic resonance spectra, by comparison to synthetic standards, and by chemical transformations. Dihydrodiols, phenols, and hydroxymethyl derivatives of 12-fluoro-5-methylchrysene were characterized. The extents of formation of 1,2-dihydro-1,2-dihydroxy-12-fluoro-5-methylchrysene and 7,8-dihydro-7,8-dihydroxy-12-fluoro-5-methylchrysene in mouse liver in vitro were strongly influenced by pretreatment with 3-methylcholanthrene, but the ratio of 1,2-dihydrodiol to 7,8-dihydrodiol was lower than in the metabolism of 5-methylchrysene carried out under identical conditions. The major metabolites of [3H]-12-fluoro-5-methylchrysene formed in mouse epidermis, 0.33 to 4 hr after topical application, were 7,8-dihydro-7,8-dihydroxy-12-fluoro-5-methylchrysene and 7-hydroxy-12-fluoro-5-methylchrysene. The ratio of 7,8-dihydro-7,8-dihydroxy-12-fluoro-5-methylchrysene to 1,2-dihydro-1,2-dihydroxy-12-fluoro-5-methylchrysene in mouse epidermis, 2 hr after application of [3H]-12-fluoro-5-methylchrysene, was 68:1, compared to 1:1 for the corresponding dihydrodiols of 5-methylchrysene. These results show that fluorine substitution at the 12-peri position of 5-methylchrysene inhibits formation of the 1,2-dihydrodiol in the adjacent ring. Since the 1,2-dihydrodiol is a major proximate carcinogen of 5-methylchrysene, the results provide an explanation for the relatively low carcinogenicity of 12-fluoro-5-methylchrysene.

Identification of the major adducts formed by reaction of 5-methylchrysene anti-dihydrodiol-epoxides with DNA in vitro

5-Methylchrysene is metabolically converted to the bay-region dihydrodiol-epoxides, trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (DE-I), in which the methyl group and the epoxide ring are in the same bay region, and trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydro-5-methylchrysene (DE-II). Previous studies have indicated that DE-I is more important in 5-methylchrysene carcinogenesis than is DE-II. Both DE-I and DE-II were individually reacted with calf thymus DNA in vitro. The DNA was enzymatically hydrolyzed to deoxyribonucleosides, and the modified deoxyribonucleosides were separated by chromatography on Sephadex LH-20 and analyzed by high-performance liquid chromatography. One major adduct and seven minor adducts were formed from each dihydrodiol-epoxide. The major adduct was, in each case, characterized by its pH-dependent partition coefficient, stability to base, mass spectrum, ultraviolet spectrum, and nuclear magnetic resonance spectrum as a deoxyguanosine derivative resulting from addition of the exocyclic amino group of deoxyguanosine to the benzylic carbon of the epoxide ring of the dihydrodiol-epoxide. The results of this study show that the major DNA adducts formed from 5-methylchrysene via DE-I and DE-II are structurally similar.

Dose-response study of the carcinogenicity of tobacco-specific N-nitrosamines in F344 rats

Tobacco and tobacco smoke contain relatively high amounts of four tobacco-specific N-nitrosamines. Of these, N-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and N'-nitrosoanatabine (NAT) were bioassayed at three dose levels by subcutaneous injections into male and female F344 rats in 60 subdoses amounting in total to 9,3, and 1 mmol/kg. Compared with the solvent control group (trioctanoin), both NNN and NNK induced significant numbers of tumors of the nasal cavity (P less than 0.01) at all three dose levels in both male and female rats. Significant numbers of tumors were also induced by NNK in the lung at all three dose levels and in the liver at the highest dose level (P less than 0.05). In addition to nasal tumors NNN also induced esophageal tumors at a significant rate in male rats at the high and medium dose levels and in female rats at the high level (P less than 0.05); NAT was inactive at the three doses tested. Bioassays at lower dose levels as well as biochemical studies are strongly indicated for NNN and NNK since these nitrosamines occur in relatively high amounts in both chewing tobacco and tobacco smoke.

Identification of metabolites of benzo[b]fluoranthene

The metabolism by rat liver 9000 x g supernatant of the environmental carcinogen benzo[b]fluoranthene was investigated. The major metabolites were identified, by comparison to synthetic samples, as 5- and 6-hydroxybenzo[b]fluoranthene and 4- and 7-hydroxybenzo[b]fluoranthene. The principal dihydrodiol metabolite formed under these conditions was trans-11,12-dihydro-11,12-dihydroxybenzo[b]fluoranthene, which was identified by comparison to the synthetic compound. 1,2-Dihydro-1,2-dihydroxybenzo[b]fluoranthene was identified, by its mass spectrum and by comparison if its u.v. spectrum to that of a synthetic model compound, 11-ethylidene-11H-benzo[b]fluorene. No evidence was obtained for the formation of 7b,8-dihydro-7,8-dihydroxybenzo[b]fluoranthene or trans-9,10-dihydro-9,10-dihydroxybenzo[b]fluoranthene. The latter would be the precursor to a bay region dihydrodiol epoxide of benzo[b]fluoranthene.

Identification of metabolites of 5,11-dimethylchrysene and 5,12-dimethylchrysene and the influence of a peri-methyl group on their formation

We investigated the in vitro metabolism by mouse and rat liver 9000 x g supernatant of the strong tumor initiator, 5,11-dimethylchrysene (5,11-diMeC) and its inactive analogue, 5,12-dimethylchrysene (5,12-diMeC). Ethyl acetate soluble metabolites were separated by h.p.l.c. and identified by their u.v. and m.s. and by comparison to selected synthetic reference standards. Both compounds were converted to dihydrodiols, chrysenols, hydroxymethylchrysenes, and hydroxymethylchrysenols. The peri 12-methyl group of 5,12-diMeC strongly inhibited metabolism at the adjacent 1,2-positions. Thus, the ratio of 7-hydroxy-5,12-diMeC to 1-hydroxy-5,12-diMeC was approximately 100 to 1 when 5,12-diMeC was metabolized by liver supernatants from 3-methylcholanthrene pretreated mice and rats. In addition, 7,8-dihydro-7,8-dihydroxy-5,12-diMeC was preferentially formed over 1,2-dihydro-1,2-dihydroxy-5,12-diMeC by liver supernatants from control, 3-methylcholanthrene pretreated, and Aroclor pretreated animals. In contrast, the presence of a methyl group at the 11 position of 5,11-diMeC did not inhibit formation of 1-hydroxy-5,11-diMeC or 1,2-dihydro-1,2-dihydroxy-5,11-diMeC. Since 1,2-dihydro-1,2-dihydroxy metabolites of 5-methylchrysene derivatives are potential proximate tumorigens, these results may provide a basis for the higher tumorigenicity of 5,11-diMeC than of 5,12-diMeC.

Tumour initiating activity of dihydrodiols of benzo[b]fluoranthene, benzo[j]fluoranthene, and benzo[k]fluoranthene

The tumor initiating activities on mouse skin of benzo[b]fluoranthene, (B[b]F), benzo[j]fluoranthene (B[j]F), benzo[k]fluoranthene (B[k]F] and three of their dihydrodiols, 9,10-dihydro-9,10-dihydroxybenzo[b]fluoranthene (B[b]F-9,10-diol), 9,10-dihydro-9,10-dihydroxybenzo[j]fluoranthene (B[j]F-9,10-diol), and 8,9-dihydro-8,9-dihydroxybenzo[k]fluoranthene (B[k]F-8,9-diol) were evaluated. Among the parent hydrocarbons, B[b]F was the most potent tumor initiator, with activity greater than that of B[j]F but less than that of benzo[a]pyrene. B[k]F also showed tumor initiating activity, in contrast to its lack of complete carcinogenic activity on mouse skin. B[b]F-9,10-diol, which can form a bay region dihydrodiol epoxide, was as active as B[b]F. B[j]F-9,10-diol, which would form its dihydrodiol epoxide in a four sided pseudo-bay region, was less active than B[j]F. B[k]F-8,9-diol was inactive. These results, together with parallel metabolic studies, suggest that the formation of bay region dihydrodiol epoxides may not be the major activation mechanism in benzofluoranthene tumorigenesis.

Effects of gonadotrophin treatment in vivo on testicular function in immature rhesus monkeys (Macaca mulatta)

Changes in testicular histology and concentrations of testosterone and oestradiol 17 beta in testicular tissue and plasma have been studied following administration of gonadotrophins (oFSH, oLH, hCG and PMSG) to immature male monkeys. Treatment with FSH (1 mg/day) or PMSG (100 IU/day) for five days, induced a marked enlargement of the seminiferous tubules and increase in the Sertoli cell cytoplasm. Injections of LH (1 mg/daily) or hCG (100 IU/daily) administered similarly, failed to produce hypertrophy of the Sertoli cell. In LH, hCG and PMSG stimulated testes morphologically differentiated interstitial cells could be recognized. FSH did not produce any detectable effect on the intertubular tissue. A significant increase in testicular and plasma testosterone levels was observed with LH, hCG and PMSG. FSH was shown to be much less effective in stimulating androgenesis. An increase in testicular oestradiol production over that of controls, was observed in FSH and PMSG treated monkeys but not in animals treated with LH or hCG.

Three or four copies of a dicentric 17q isochromosome in an acute myeloproliferative disorder

The majority of metaphases in the bone marrow of a male patient aged 72 with a rapidly evolving aleukemic erythremic myelosis had 48 chromosomes with three copies, or 49 chromosomes with four copies, of an i(17q), which was seen to be dicentric in C-banded and Giemsa-11-banded preparations. There was also loss of a chromosome No. 5 and the addition of a chromosome resembling a No. 22. The presence of multiple copies of the isochromosome is postulated to be related to the acuteness of the condition.