Effects of 3-aminobenzamide on the post-initiation phase of N-nitrosobis(2-oxopropyl)amine induced pancreatic carcinogenesis in Syrian hamsters.

Effects of 3-aminobenzamide (ABA) on pancreatic carcinogenesis after initiation by N-nitrosobis(2-oxopropyl)amine (BOP) were investigated in Syrian hamsters. Animals were given BOP at a dose of 70 mg/kg body weight by subcutaneous injection and following a 2-week recovery period, were administered basal diet or basal diet containing 0.5, 0.75 and 1.5% ABA for 30 weeks. While the incidences of resultant pancreatic lesions, including hyperplasia, atypical hyperplasia and carcinoma, induced by BOP were not significantly influenced by ABA treatment, the mean numbers of those pancreatic lesions were significantly decreased in a dose-dependent way. The results therefore suggested the possible involvement of poly(ADP-ribosyl)ation in the post-initiation phase of pancreatic carcinogenesis in hamsters.     

Modulation of A N-nitrosobis(2-hydroxypropyl)amine-induced carcinogenesis by clofibrate in hamsters

The effects of clofibrate treatment on N-nitrosobis(2-hydroxy-propyl)amine(BHP) induced liver, gall bladder, pancreas, lung and kidneycarcinogenesis in hamsters were studied. Animals were givenBHP as an initiator at a dose of 500 mg/kg body weight subcutaneouslyonce a week for 5 weeks followed by diet containing 0.25 or0.5% clofibrate for 30 weeks. Both doses of clofibrate promotedhepatocarcino-genesis as judged from the associated multiplicityof liver lesions including hyperplastic nodules and hepatocellularcarcinomas. -Glutamyltranspeptidase (-GTP) activity was notexpressed in those lesions in the liver of hamsters given BHPfollowed by a basal diet or diets containing clofibrate. Clofibrateat a dose of 0.5% in the diet, in contrast, inhibited the developmentof pancreatic adenocarcinomas and lung neoplasms, includingadenomas and adenocarcinomas, without affecting carcinogenesisin the gall bladder and kidney. These results clearly indicatedifferectial modification potential of clofibrate for BHP-inducedliver, pancreas and lung carcinogenesis in Syrian hamsters.     

Effects of phenobarbital and secondary bile acids on liver, gallbladder, and pancreas carcinogenesis initiated by N-nitrosobis (2-hydroxypropyl)amine in hamsters

The effects of dietary administration of phenobarbital [(PB) CAS: 50-06-6] or the secondary bile acids, deoxycholic acid [(DCA) CAS: 83-44-3] and lithocholic acid [(LCA) CAS: 434-13-9], on tumorigenesis in the liver, gallbladder, and pancreas were investigated in male Syrian golden hamsters after carcinogenic initiation by N-nitrosobis(2-hydroxypropyl)amine [(BHP) CAS: 53609-64-6]. BHP [500 mg/kg (body wt)] was injected sc once weekly for 5 weeks. The animals were then maintained on a basal diet or a diet containing either 0.05% PB, 0.1% DCA, 0.5% DCA, or 0.5% LCA for 30 weeks. DCA enhanced the development of cholangiocarcinomas without influencing that of hepatocellular lesions. PB promoted the induction of hepatocellular carcinomas but not that of cholangiocarcinomas. LCA was without effect on the induction of either hepatocellular carcinomas or cholangiocarcinomas. DCA at a dose of 0.5% enhanced the induction of polyps in the gallbladder. Both DCA, at a dose of 0.1%, and LCA significantly enhanced the induction of pancreas carcinomas. PB had no effect on the induction of polyps in the gallbladder or of pancreas carcinomas. These data document that different tumors may be differentially promoted following initiation with a common carcinogen.     

Combined effects of cholecystectomy and lithocholic acid on pancreatic carcinogenesis of N-nitrosobis(2-hydroxypropyl)amine in Syrian golden hamsters

The effects of cholecystectomy and/or lithocholic acid (LCA) on the composition of biliary bile acid and on pancreatic carcinogenesis by N-nitrosobis(2-hydroxypropyl)amine (BHP) were examined in male Syrian golden hamsters. Cholecystectomy was performed 1 wk before BHP initiation. BHP (250 mg/kg of body weight) was injected s.c. once a wk for 5 wk. A diet containing 0.5% LCA was begun 1 wk after the final BHP injection. All hamsters were sacrificed 36 wk after cholecystectomy, and the pancreas was examined histologically. Only the LCA treatment but no other treatment influenced the bile acid composition, i.e., the increase in LCA and decrease in cholic acid. The incidence of pancreatic carcinoma was 23 of 30 (76.7%) in hamsters receiving cholecystectomy plus BHP followed by LCA diet. The tumor incidence was five of 18 (27.8%) with BHP followed by basal diet, ten of 18 (55.6%) with cholecystectomy plus BHP followed by basal diet, and six of 18 (33.3%) with BHP followed by LCA diet, respectively. The total number of pancreatic carcinomas in hamsters receiving cholecystectomy and BHP followed by LCA diet also increased significantly. These results indicate that combined treatments of cholecystectomy and dietary LCA enhanced BHP-inducing pancreatic carcinogenesis in hamsters.     

Inhibition by catechol and di(2-ethylhexyl)phthalate of pancreatic carcinogenesis after initiation with N-nitrosobis(2-hydroxypropyl)amine in Syrian hamsters

The effects of dietary administration of catechol (CC), paramethylcatechol(PMC) and di(2-ethylhexyl)phthalate (DEHP) were compared withthat of butylated hydroxjanisole (BHA) in Syrian hamsters initiatedwith N-nitrosobis(2-hydroxypropyl)amine (BHP). Development ofpancreatic atypical hyperplasias and adenocarcinomas in termsof combined multiplicity was significantly reduced by CC andDEHP. A similar slight but non-significant tendency was observedfor BHA, while PMC was without effect. No statistically significantreduction of liver or gall bladder lesions was observed. Theresults thus suggest that both antioxidant and peroxisome proliferatorcategories of agents can inhibit pancreatic carcinogenesis inhamsters.     

Ki-ras activation in pancreatic carcinomas of Syrian hamsters induced by N-nitrosobis(2-hydroxypropyl)amine.

Five pancreatic carcinomas induced by N-nitrosobis(2-hydroxypropyl)amine in Syrian golden hamsters were analyzed for activation of Ki-ras at codons 12 and 13, using the polymerase chain reaction and direct sequencing. The Ki-ras gene was shown to be activated in four of the five carcinomas, and the results were further confirmed by subcloning and sequencing. All the mutations involved a G-to-A transition at the second position of codon 12, which resulted in a change at the amino acid level from glycine to aspartic acid. This mutation is identical with that reported for pancreatic tumors of Syrian hamsters induced by N-nitrosobis(2-oxopropyl)amine.     

Carcinogenicity of N-nitrosobis(2-hydroxypropyl)amine and N-nitrosobis(2-oxopropyl)amine in MRC rats.

Weekly sc injections of equitoxic doses of N-nitrosobis(2-hydroxypropyl)amine (BHP) and N-nitrosobis(2-oxopropyl)amine (BOP) to Wister-derived MRC rats induced tumors. The incidence, latency, multiplicity, morphologic type, and distribution of these tumors varied according to the compound given. The esophagus was the main target organ for BHP (100%), followed by the respiratory tract (87%), pharynx (80%), colon and liver (each 73%), kidneys (20%), thyroid gland (20%), and urinary bladder and urethra (each 7%). BOP was ineffective in the esophagus and pharynx but induced a higher incidence of tumors in the kidneys (27%), thyroid gland (60%), urinary bladder (33%), and urethra (73%) and fewer neoplasms in the respiratory tract (20%), colon (67%), and liver (53%). In addition, BOP caused a few, apparently primary, prostate squamous cell carcinomas. The results are compared with results of BHP treatment in Sprague-Dawley rats and with results of BHP and BOP treatment in Syrian golden hamsters.     

Effects of catechol and its analogs on pancreatic carcinogenesis initiated by N-nitrosobis(2-oxopropyl)amine in Syrian hamsters

The modifying effects of the phenolic antioxidant catechol (CC) and its analogs hydroquinone (HQ) and resorcinol (RN) on pancreatic carcinogenesis were evaluated in 146 female Syrian golden hamsters. Groups of animals received either saline or 70 mg/kg body wt N-nitrosobis(2-oxopropyl)amine (BOP) s.c. injections, twice with a 2 week interval, followed by basal diet or diet containing 1.5% of CC, HQ or RN, and 0.75% CC from week 4. All hamsters were killed at week 20 and histopathologically examined for development of pancreatic, liver and gall bladder lesions. The total numbers of pancreatic lesions comprising carcinomas, atypical ductal hyperplasias and ductal hyperplasias per hamster were significantly decreased in animals receiving BOP followed by CC, HQ and RN when compared to those in hamsters given BOP followed by basal diet. Incidence values for atypical ductal hyperplasias were also significantly decreased by the RN or 0.75% CC treatments. The results thus suggest that pancreatic carcinogenesis initiated by BOP in Syrian hamsters can be inhibited by treatments with phenolic antioxidants such as CC, HQ and RN for a relatively short experimental period.     

Determination of N-nitrosobis(2-hydroxypropyl)amine in environmental samples

N-Nitrosobis(2-hydroxypropyl)amine (ND2HPA) is a potent pancreatic carcinogen in hamsters and induces gastrointestinal and respiratory tract cancer in rats. The precursor amines, diisopropanolamine (Di-PA) and triisopropanolamine (Ti-PA), are used in some manufacturing processes and in cosmetic preparations. We have found low levels of ND2HPA in commercial Ti-PA (21-270 ng/g) and in Di-PA (20-1 300 ng/g) and have demonstrated that ND2HPA is formed from Ti-PA and nitrite in a yield comparable to that observed for formation of N-nitrosodiethanolamine (NDELA) from triethanolamine under relatively mild conditions. After reaction for 4 h at 37 degrees C (10 mmol/L amine, 40 mmol/L nitrite, pH 3.0), the ND2HPA yield was 0.51%. The NDELA yield under the same conditions was 0.96%. ND2HPA was determined by gas chromatography-thermal energy analysis (GC-TEA) and GC-high-resolution mass spectrometry (GC-MS) selected ion monitoring of the tert-butyldimethylsilyl (t-BDMS) ether after extraction on a Celite 560 column. The t-BDMS ethers of ND2HPA and NDELA yielded intense, structurally significant peaks at m/z 333.2030 and 305.1716, respectively. The GC-MS procedure provides sensitivity and selectivity comparable to that of GC-TEA.     

Inhibition by methionine of pancreatic carcinogenesis in hamsters after initiation with N-nitrosobis(2-oxopropyl) amine

The modifying effects of dietary L-methionine in the post-initiation phase of pancreatic carcinogenesis were investigated in hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). Groups consisting of 20 and 30 animals, respectively, were given BOP subcutaneously, once a week five times at a dose of 10 mg/kg body wt. and then continuously fed diet supplemented with 2% (group 1) or 0% (group 2) methionine (weeks 5-32). After five subcutaneous injections of saline, group 3 animals were similarly fed diet supplemented with 2% methionine for the same period. The incidence of pancreatic ductal adenocarcinomas was significantly lower in group 1 (36.8%, P<0.05) than in group 2 (71.4%). Multiplicity of adenocarcinomas was also significantly lowered (0.52 and 1.28/hamster, P<0.05). Similarly, total numbers of combined adenocarcinomas and dysplastic lesions were significantly decreased in group 1 (2.05, P<0.05) as compared with group 2 (3.67). Methionine enhanced atrophic change of pancreatic acinar cells in hamsters given BOP, indicating that the inhibitory effects on the post-initiation stage of BOP-induced pancreatic carcinogenesis in hamsters could be generally linked to suppression of growth.     

Prostatic cancer induced in MRC rats by N-nitrosobis(2-oxopropyl)-amine and N-nitrosobis(2-hydroxypropyl)amine

Weekly intragastric treatment with N-nitrosobis(2-oxo-propyl)amineor N-nitrosobis(2-hydroxypropyl)amine induced hyperplastic,preneoplastic and neoplastic prostatic changes in >80% ofMRC rats. The lesions initially appeared as focal or multifocalproliferations of alveolar epithelium in a cribriform patternwhich, in all but one case, underwent progressive changes, oftentending toward squamous cell formation. Tumors, found primarilyin the ventral prostate, demonstrated various degrees of differentiationand invasive growth. A few neoplasms developed in the seminalvesicles; however all were of a glandular type. The sequentialalteration of induced lesions is described and the possiblereasons for the squamous cell character of most tumors discussed.Prostatic cancer induction by systemic application of specificnitrosamines could provide a unique tool for investigating importantaspects of the disease.     

Mutagenicity in V79 cells of N-nitrosobis(2-hydroxypropyl)amine and N-nitrosobis(2-oxopropyl)amine activated by tissues from hamsters fed low and high fat diets.

Hepatocytes and pancreas duct tissues from male Syrian hamsters fed high-fat (HFD) and low-fat (LFD) diets were used to activate N-nitrosobis(2-hydroxypropyl)amine (BHP) and N-nitrosobis(2-oxopropyl)amine (BOP) in the V79 cell mutagenicity assay. V79 DNA alkylation by BHP and BOP was also measured. There was a 3.5-fold increase in BHP mutagenicity but only a 1.4-fold increase in BOP mutagenicity when hepatocytes from HFD-fed hamsters were used over the mutagenicity when hepatocytes from LFD-fed hamsters were used. When pancreas duct tissue was the activating system there was a 2-fold increase in BHP and BOP mutagenicity. O6-Methylguanine levels in V79 DNA rose 4-fold when hepatocytes from HFD-fed hamsters were used to activate BOP but they declined when BHP was the alkylating agent.     

Sex differences in the effects of retinoids on carcinogenesis by N-nitrosobis(2-oxopropyl)amine in Syrian hamsters

Syrian hamsters were given in a single dose of N-nitrosobis(2-oxopropyl)-amine (BOP) (40 mg/kg, s.c.) and 1 week later were fed 1 of 4 retinoid types (13-cis-retinoic acid (13-cis-RA), N-ethylretinamide (ERA), 2-hydroxyethylretinamide (OH-ERA), or 4-hydroxyphenylretinamide (PRA)) each at 3 levels (0.05, 0.1, 0.2 mM/kg diet). The pancreatic carcinoma incidence was not influenced significantly by feeding retinoids. The pancreatic adenoma incidence, however, was reduced by feeding each of the retinoids to female hamsters, with the reduction varying with the retinoid fed (13-cis-RA greater than ERA and OH-ERA greater than PRA). In male hamsters increased numbers of pancreatic adenomas were observed after feeding OH-ERA and PRA. Tumors induced in other tissues were reduced by retinoids in females, but not in males. Females fed 13-cis-RA and ERA had a lower incidence of gall bladder polyps, and feeding OH-ERA reduced the liver tumor incidence. Food consumption and serum alkaline phosphatase ans aspartate amino transferase activities were not influenced by BOP or retinoid type or level. Body and pancreas weight were influenced by retinoid level, but the effects were not consistently dose-related.     

Distribution and metabolism of N-nitrosobis(2-hydroxypropyl)amine in rats

The metabolic fate of the lung carcinogen N-nitrosobis(2-hydroxypropyl)amine (ND2HPA) in male Wistar rats was studied. The blood level after a single intraperitoneal (i.p.) injection of [1-14C]-ND2HPA at a dose of 3 g/kg body weight reached a maximum within 1 h. Most of the administered 14C was eliminated via the urine; 90.8% of the 14C was excreted in urine within 24 h, 5.5% in faeces, and 3.2% in expired air. About 11% of the 14C was detected in bile collected over 24 h. A relatively high concentration of 14C was found in the blood and target organs, such as the lung, liver, thyroid gland and kidney 1 h after treatment. Analysis by high-pressure liquid chromatography showed that the 14C in the blood and urine was mostly accounted for by unchanged ND2HPA, together with smaller amounts of N-nitroso-(2-hydroxypropyl)(2-oxopropyl)amine (N2HP2OPA). ND2HPA and N2HP2OPA were also detected in the lung and liver of rats 30 min to 12 h after the administration and were present in higher concentrations in the blood and lung than in the liver and pancreas. Besides ND2HPA and N2HP2OPA. N-nitrosomethyl(2-hydroxypropyl)amine (NM2HPA) was also found in urine collected over 6 h. ND2HPA, N2HP2OPA and NM2HPA showed mutagenicity in the Salmonella assay system with metabolic activation by a 9000 X g supernatant of rat liver, and N2HP2OPA was also mutagenic in the presence of a rat lung preparation. These data suggest that N2HP2OPA and NM2HPA might be important intermediates in the metabolic activation of ND2HPA to its ultimate carcinogenic form in rats.     

Effects of various prostaglandin synthesis inhibitors on pancreatic carcinogenesis in hamsters after initiation with N-nitrosobis(2-oxopropyl)amine

The effects of prostaglandin synthesis inhibitors on development of N-nitrosobis(2-oxopropyl)amine (BOP)-initiated pancreatic tumors were investigated. Female Syrian golden hamsters were given five weekly s.c. injections of BOP (10 mg/kg body weight) during the first 5 weeks and then given 20 p.p.m. indomethacin in the drinking water, 0.25% phenylbutazone in the diet, 1% aspirin in the diet, or no treatment (control group). The resultant incidence of pancreatic carcinoma at week 32 was significantly lower (P less than 0.05) in animals receiving phenylbutazone (36.8%) than in the controls (71.4%) and the numbers of carcinomas per hamster were significantly reduced by indomethacin (0.63) and phenylbutazone (0.58) treatment compared with the control group value (1.29). Aspirin also showed a tendency to decrease pancreatic tumor incidence, but this was not significant. Thus, prostaglandin synthesis inhibitors reduce the development of pancreatic cancer when administered during the post-initiation phase in this animal model.     

High mutagenic activity of N-nitrosobis(2-oxopropyl)amine and N-nitrosobis(2-hydroxypropyl)amine in the host-mediated assay in hamsters: evidence for premutagenic methyl and hydroxylpropyl adducts

The carcinogenic nitrosamines N-nitrosobis(2-oxopropyI)-amine(BOP) and N-nitrosobis(2-hydroxypropyl)amine (BHP) were testedin excision-repair-deficient strains of his G46 Salmonella mutantsin the intrasanguinous host-mediated mutagenesis assay (HMA)in male Syrian hamsters. The major adducts produced by BOP inthe hamster are methylguanines, while BHP leads to hydroxypropylguaninesas well as methylguanines. Both nitrosamines were potent mutagensin bacteria recovered from the liver. On a comparison of administereddose, BOP was more potent, but when compared at doses producingsimilar levels of O⁶-methylguanine (O⁶MeG) in host liver DNA,or at equitoxic doses in the hamster, BHP was more potent. BHPwas 10 times less mutagenic in an excision-repair-proficientstrain of Salmonella, but the mutagenicity of BOP was not reduced.The effects of excision repair on in vitro mutagenesis inducedby the direct-acting analogs N-(2-oxopropyl)-N-nitrosourea (OPNU),a methylating agent, and N(2-hydroxypropyl)-N-nitrosourea (HPNU),a hydroxypropylating agent, were also examined. Mutagenesisby HPNU, but not OPNU was very sensitive to excision repair.Thus BOP appears to lead to mutagenesis via methylation, whilemutagenesis by BHP apparently proceeds via hydroxypropylation.BOP, BHP, OPNU and HPNU were several times less mutagenic inhisG428 than hisG46 strains. In contrast to hisG46 strains,which are reverted mainly by base-pair substitutions at G: Cbase pairs, hisG428 strains are generally more sensitive tomutagenesis at A: T base pairs. Taken together the above resultsand observations that >90% of the adducts from BOP and BHPwere alkylguanines, suggest that the major premutagenic adductsproduced from BOP and BHP are alkylguanines as opposed to otheralkylated bases. BOP and BHP were weak mutagens in the Salmonella/S-9mutagenesis assay using hamster liver S-9 fraction. When comparedwith results in the HMA, BOP and BHP were orders of magnitudeless mutagenic in vitro. This observation suggests: (i) thepathways or enzymes involved in the activation of these carcinogens(although uncertain) may be different in vivo and in vitro;or (ii) the pathways for the in vitro and in vivo metabolismmay be similar, but the conditions used for the in vitro activationof these nitrosamines are inadequate to generate significantlevels of nitrosamine metabolites.     

Carcinogenic activity of endogenously synthesized N-nitrosobis(2-hydroxypropyl)amine in rats administered bis(2-hydroxypropyl)amine and sodium nitrite

The carcinogenic activity of endogenously synthesized N-nitrosobis(2-hydroxypropyl)amine(BHP) was investigated in male Wistar rats administered bis(2-hydroxypropyl)amine(BHPA) mixed in powder diet at a concentration of 1%, and sodiumnitrite (SN) dissolved in distilled water at concentrationsof 0.15 and 0.3%, for 94 weeks. Urinary excretion of BHP wasdetected in rats given 1% BHPA and 0.3% SN but not in the groupsreceiving either of these precursors alone. Nasal cavity, lung,esophagus, liver and urinary bladder tumors were found in animalstreated with combinations of 1% BHPA and 0.15 or 0.3% SN, suggestingthat the target organs of the endogenously synthesized BHP aresimilar to those affected when the carcinogen is administeredexogenously. The incidences of nasal cavity and lung tumorsreached 74 and 58% in rats given 1% BHPA and 0.3% SN, respectively.Tumors at sites other than target organs were only found atlevels similar to those previously reported for spontaneoustumors in male Wistars. The present results clearly indicatedthe tumor inducibility of a nhrosatable amine, BHA, throughan endogenous nitrosation by feeding to rats in conjunctionwith nitrite, and provide further suggestive evidence that endogenousnitrosations of environmental nitrosatable amines can be a potentialrisk factor in human cancer development.     

Inhibitory effects of sulfation inhibitors on initiation of pancreatic ductal carcinogenesis by N-nitrosobis(2-oxopropyl)amine in hamsters

The effects of dehydroepiandrosterone sulfate (DHAS), a typicalhydroxysteroid sulfotransferase (HSTase) inhibitor, and of 3'-phosphoadenosine5'-phosphate (PAP), a nonspecific sulfation inhibitor on N-nitrosobis(2-oxopropyl)-amine(BOP)-induced initiation were examined in a rapid productionmodel for pancreatic carcinomas in hamsters in order to elucidatethe involvement of sulfotransferase in the metabolic activationof ß-oxypropylnitrosamines. While neither low norhigh doses of DHAS and PAP exerted any significant influenceon the incidence of ductal lesions including carcinomas, thehigh dose of DHAS (350 mg/kg body wt) and a both low (90 mg/kg)and high (180 mg/kg) doses of PAP reduced the mean numbers ofpancreatic ductal adenocarcinomas. The high dose of PAP alsoreduced the number of all ductal lesions combined. The resultsthus suggest that metabolic activation with STase is involvedin BOP-induced pancreatic ductal carcinogenesis in hamsters,and support the hypothesis that BOP is metabolized to ß-hydroxyalkylnitrosaminesfollowed by activation to proximate sulfuric acid esters byHSTase.     

Alkylation of rodent tissue DNA induced by N-nitrosobis(2-hydroxypropyl)amine.

Levels of methyl and hydroxypropyl adducts induced by single s.c. injections of various doses of tritium-labeled N-nitrosobis(2-hydroxypropyl)amine ([1-3H]BHP) were determined in the liver, pancreas, kidney and lung of hamsters and rats. At doses of BHP used in carcinogenesis studies (100-500 mg/kg), methylation of DNA was more extensive than its hydroxypropylation; however, it did not increase proportionally with the dose and gradually became secondary to hydroxypropylation at higher doses of the carcinogen. Ratios of hydroxypropyl versus methyl adducts also varied significantly depending on the tissue and species. In both species ratios of N7-hydroxypropylguanine (N7-HpG) versus N7-methylguanine (N7-MeG) were greater in kidney and pancreas than in liver or lung. Due to apparent differences in the repair of O6-methylguanine (O6-MeG) and O6-hydroxypropylguanine (O6-HpG), and the propensity of 2-hydroxypropylating as compared to methylating agents to yield a greater percentage of oxygen adducts, ratios of O6-HpG versus O6-MeG were markedly greater than those of N7-HpG versus N7-MeG. Levels of O6-HpG were greater than those of O6-MeG in rat liver, pancreas and kidney and also in hamster kidney, while such levels were similar in rat lung and also in hamster liver, pancreas and lung. Like N-nitrosobis(2-oxopropyl)amine (BOP) and N-nitroso(2-hydroxypropyl) (2-oxopropyl)amine (HPOP), BHP was activated primarily in the liver and induced substantially greater DNA damage in this than in any other tissue examined. However, unlike BOP and HPOP, which induced similar levels of hepatic DNA damage in the above two species, BHP methylated and hydroxypropylated hamster liver DNA more extensively than that of the rat. Differences between BOP and BHP were also observed regarding levels and distribution of DNA adducts in extrahepatic tissues. In rats, BHP induced greater levels of methylation and hydroxypropylation in lung than in kidney, while the reverse was observed with BOP. Apparently reduction of the beta-carbon of pancreas-specific nitrosamine carcinogens results in a shift of alkylation from kidney to the lung. Excretion of HPOP in the urine of BHP-treated animals and the observed saturation of DNA methylation at high doses of BHP, supported the hypothesis that the BHP-induced methylation of DNA proceeded via the intermediate formation of HPOP. This was further supported by the observation that both excretion of HPOP and levels of methyl adducts were greater in hamsters than in rats.(ABSTRACT TRUNCATED AT 400 WORDS)