DNA adducts of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in colon, bladder, and kidney of congenic mice differing in Ah responsiveness and N-acetyltransferase genotype

Heterocyclic amines, suspected as cancer initiators, require metabolic activation to exert genotoxicity. The food carcinogen 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ) undergoes activation via N-hydroxylation by cytochrome P450 1A2, followed by O-esterification by N-acetyltransferase. We examined the effects of the Ah locus and acetylator polymorphisms (implicated in human colon and bladder cancer risk) on levels of 32P-postlabeled IQ-DNA adducts in C57BL/6 mice congenic for slow acetylation and/or Ah nonresponsiveness. Some were pretreated with beta-naphthoflavone (beta NF), an inducer of cytochromes P450 1A. Guanine adducts were detected in all organs, the predominant one corresponding to N2-(deoxyguanosine-8-yl)-IQ. In the kidney, beta NF pretreatment reduced total adducts by 50% in Ah-responsive animals (P = 0.021); the Ah or acetylator phenotype did not otherwise affect total adducts. In the colon of Ah-nonresponsive animals, rapid acetylators had 3-fold more adducts than slow acetylators (P = 0.0001, vehicle-pretreated; P = 0.0031, beta NF-pretreated). In Ah-responsive mice of either acetylator phenotype, beta NF pretreatment reduced total adducts in the colon by 70% (P = 0.0003). A significant interaction of phenotypes occurred in the bladder; beta NF-pretreatment caused a 2.5-fold increase in adducts but only in the Ah-responsive, rapid acetylator mice. In sum, these polymorphisms influenced the level of IQ-DNA adducts in the kidney, urinary bladder, and colon in complex ways.

Has the use of cervical, breast, and colorectal cancer screening increased in the United States?

This report describes trends in reported breast, cervical, and colorectal cancer screening within the US population from 1987 to 1992. Data from the 1987 and 1992 Cancer Control Supplements of the National Health Interview Survey were analyzed to determine use of Pap smears by women aged 18+; of mammography and clinical breast examination by women aged 50+; and of proctoscopy, digital rectal examination, and fecal occult blood testing among men and women aged 50+. Use of mammography doubled between 1987 and 1992 while Pap smear use changed very little. Use of the three colorectal cancer screening modalities increased but levels remained low. Usage trends were also assessed in relation to several sociodemographic factors. Disparities in screening reported in 1987 according to income and education persisted in 1992.

Promotion of N-nitrosodimethylamine-initiated mouse lung tumors following single or multiple low dose exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin

The environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is highly toxic to several rodent species and may have adverse health effects in exposed human populations. Further, TCDD has been shown to be a potent liver tumor promoter in the rat after repeated administration. These studies were conducted to determine the tumor promoting capability of TCDD in the Swiss mouse following single or multiple exposures. Following tumor initiation with N-nitrosodimethylamine (NDMA; 25 mg/kg), animals were given either a single dose (1.6, 16 or 48 micrograms/kg) or repeated injections (0.05 microgram/kg/week for 20 weeks) of TCDD and sacrificed at 52 weeks of age. Neither NDMA nor TCDD caused an increase in incidence of liver tumors. NDMA induced lung tumors in 100% of animals, with 12 +/- 0.1 tumors/mouse. The multiplicity of lung tumors was significantly increased by low dose TCDD treatment, with 20 +/- 2.6 tumors/mouse following a single 1.6 micrograms/kg dose (P = 0.016) and 18 +/- 1.7 (P = 0.031) following repeated 0.05 microgram/kg doses (x 20). Higher doses of TCDD did not increase multiplicity of lung tumors and, in fact, may have been toxic to the lungs of NDMA-treated mice, as evidenced by the infiltration of pigmented macrophages. These data demonstrate the potent tumor promoting capability of TCDD in mouse lung.

Suppression of pulmonary P4502b and induction of hepatic, intestinal and kidney P4501a-1 and 1a-2 in the Ah-responsive and non-responsive mouse by Aroclor 1254

1. Investigations in our laboratory have demonstrated a rapid suppression of the P4502b isoform in mouse lung, concomitant with significant induction of this enzyme in liver from these same animals. The current study was designed to determine whether the suppression by polychlorinated biphenyls of pulmonary P4502b required the presence of a functional Ah receptor, and additionally to delineate the time course of the induction responses to Aroclor 1254 in the liver, kidney, and intestine of the AH-responsive and non-responsive mouse. 2. P450s were quantified by specific enzyme assay and immunoblot in liver (1a-1, 1a-2, 2b), lung (1a-1, 1a-2), kidney (1a-1, 1a-2, 2b) and small intestine (1a-1, 2b) of C57 and DBA animals at varying times (48 h-12 weeks) following a single intraperitoneal dose of Aroclor 1254 (250 mg/kg). 3. The suppression of constitutive P4502b in the lung by Aroclor was observed in both strains, but was more prominent over a longer time course in the non-responsive animals. P4502b enzyme activity was increased in the liver and intestine of both strains of mouse; however, there was a significantly greater response to Aroclor in the C57 animals. These data indicate that the AH receptor does not participate in the suppression of pulmonary P4502b, and suggests that the regulation of inducible P4502b in liver and intestine is quantitatively different between these two strains of mouse. 4. P4501a was predictably induced in all tissues examined from the C57 animal, but was largely unaffected by PCBs in the DBA strain. P4501a-2, which is also regulated by the Ah receptor, was highly induced in the liver of the responsive strain, and also increased approximately two-fold in the liver of the non-responsive animals. Kidney P4501a-2 was also modestly increased by Aroclor, only in the responsive mouse.

Transplacental carcinogenesis by cisplatin in F344/NCr rats: promotion of kidney tumors by postnatal administration of sodium barbital

Transplacental carcinogenic effects of cis-dichlorodiammineplatinum (cis-DDP) in F344 rats were investigated. Pregnant F344 rats were given a single i.p. administration of either cis-DDP (5 mg/kg body wt; group 1) or saline only (group 2) on Day 18 of gestation. Offspring of groups 1 and 2 were randomly and equally divided into two subgroups: 1a, 1b and 2a, 2b, respectively. Beginning at 4 weeks of age, offspring in groups 1b and 2b received 500 ppm of sodium barbital (NaBB) in diet, while those in groups 1a and 2a received normal diet. The experiment was terminated at 79 weeks of age. A low incidence (2/19; 10.5%) of male offspring exposed to transplacental cis-DDP (group 1a) developed renal cell adenomas. Postnatal administration of NaBB significantly enhanced this incidence (10/22; p < 0.01) in cis-DDP-initiated offspring. Also, multiple kidney tumors were more common in group 1b than any other group and three animals in this group developed frank renal cell carcinomas. cis-DDP, administered transplacentally, was a complete carcinogen for rat liver as the incidence of hepatocellular adenomas was significantly higher in offspring exposed transplacentally to cis-DDP than in those exposed to saline (20/82 vs 3/75; p < 0.05). NaBB, a known promoter of hepatocellular carcinogenesis in adult rats initiated with N-nitrosodiethylamine, failed to promote liver carcinogenesis initiated by transplacental cis-DDP. Tumors of the central nervous system (3/82; gliomas) and peripheral nervous system (2/82; schwannomas) were found only in offspring exposed transplacentally to cis-DDP. Thus, cis-DDP, administered transplacentally, was a strong initiator of renal cell tumors and a complete carcinogen for multiple organs in rat offspring.

Alcohol-related cancer risk: a toxicokinetic hypothesis

Consumption of alcoholic beverages is an accepted social custom world-wide. This makes its involvement in events contributing to human cancer risk very important. Although it is neither tumorigenic nor genotoxic in animals, ethanol can potentiate the carcinogenic risk associated with certain environmentally present agents. The reasons for such a synergistic action are speculative, but among theories postulated may be ethanol's ability to modify the toxicokinetics/dynamics of carcinogen metabolism. Experiments conducted with rodents and primates support this hypothesis, demonstrating increased exposure of posthepatic organs to nitrosamines when given in combination with ethanol, followed by enhancement of DNA adduct formation and, at least in rodents, of tumor development. In addition, ethanol may induce enzymes responsible for carcinogen activation, including hepatic cytochrome P450 2E1 in rodents and humans, and in lung, kidney, and brain in rodents. Studies have also shown that these effects can extend to the next generation via maternal and in utero fetal exposure. What impact such ethanol-induced modulations have on tumorigenesis during childhood and later stages of life needs to be investigated further.

Promotion by polychlorinated biphenyls of lung and liver tumors in mice

Polychlorinated biphenyls (PCB), which are tumor promoters, have been found in human tissues for decades. Their contribution to cancer risk may only now start to appear, due to long human cancer latency and the nature of tumor promotion. Epidemiological associations have been seen between PCB exposure or tissue content and cancer at several sites. In rodents, tumor promotion by PCBs has been little studied in tissues other than liver. Previously, in an experiment modeling infant carcinogen exposure following PCBs received in milk, lung and liver tumors, initiated neonatally in mice by the environmental nitrosamine N-nitrosodimethylamine (NDMA), were promoted by later treatment with Aroclor 1254. The present study was undertaken to confirm and characterize the effects of Aroclor 1254 on tumor number, latency, size and malignancy. Male Swiss mice were given NDMA on postnatal day 4 and Aroclor 1254 (250 mg/kg) on day 8, and killed at intervals. Eight PCB congeners were quantified in the carcasses. Incidences of mice with NDMA-initiated lung tumors at 28 weeks of age were increased 2.5-fold by PCBs. Multiplicities of lung tumors were enhanced four-fold by PCBs at 28 and 52 weeks. By 72 weeks tumor numbers were similar in the NDMA-only and NDMA-PCB groups. Liver tumors first occurred in significant numbers at 52 weeks and only in mice receiving both NDMA and PCBs. As for the lung, at 72 weeks the incidence was high in both the NDMA-only and NDMA-PCB groups. Sizes of tumors and liver carcinoma incidence were not altered by PCB treatment. Carcass analysis revealed a significant positive association between lung tumor numbers at 28 weeks and relative percentage of 2,2',4,4',5-pentachlorobiphenyl, with no other correlations. The results confirm that PCBs promote lung as well as liver tumors, by triggering the early appearance of latent initiated tumors otherwise presenting in old age.

Periodic acid Schiff reaction in childhood lymphoblastic leukaemia. The Medical Research Council Working Party on Childhood Leukaemia

AIMS

To assess the prevalence and degree of periodic acid Schiff (PAS) positivity in blast cells from children with lymphoblastic leukaemia (ALL); its association with other disease characteristics; and its clinical importance in predicting the outcome of treatment.

METHODS

Marrow slides from entrants to a large United Kingdom multicentre ALL trial (UKALL X) were batch processed and assessed blind for PAS positivity by one morphologist. Patients were classified into groups A, B, and C, corresponding to less than 1% PAS positive cells, 1-10%, and over 10%, respectively. Their PAS pattern was then compared with other clinical and pathological features of ALL and with treatment outcome.

RESULTS

Slides from 921 children were examined of which 371 (40%) were categorised as group A, 324 (35%) as group B, and 226 (25%) as group C. There was a clear association between the presence of blast cell vacuoles on Romanowsky staining and PAS positivity. Group A (PAS negative) patients included a disproportionate excess of those with L2 morphology, those under 2 or over 6 years of age, those with an initial white cell count over 50 x 10(9)/l, those with a T or null cell immunophenotype, and those with chromosomal abnormalities other than "high hyperdiploidy". Four years from diagnosis, group C patients had an 8% disease free survival advantage over those in group A (2p = 0.01). This was irrespective of initial white cell count, but not of immunophenotype or the presence of vacuoles.

CONCLUSIONS

Strong PAS positivity is a feature of "common" ALL and is particularly associated with blast cell vacuoles. It does occasionally occur in other disease subtypes with or without vacuoles. It predicts a better response to current treatment, but not independently of other cell characteristics.

Frequency and importance of change in blast cell karyotype in relapsing childhood lymphoblastic leukemia

Blast cell chromosome abnormalities at presentation in childhood acute lymphoblastic leukemia (ALL) are common, and different patterns are known to be related to outcome. In contrast, the frequency and importance of further changes at the time of relapse remain unclear. Blast cell karyotype evolution was therefore studied in a group of children with recurrent disease. Of 134 consecutive children diagnosed between 1982 and 1992, 31 had a marrow relapse, and 24 had complete cytogenetic studies at both diagnosis and the time of recurrence. Fourteen (58%) of the 24 showed additional chromosomal abnormalities at relapse, 5 (21%) retained abnormalities identical to those seen at diagnosis, and 5 (21%) remained cytogenetically normal. The 14 with additional changes had shorter first remissions and showed shorter survival after relapse compared with the others. These findings indicate that emergency of cytogenetically recognizable subclones during the progression of childhood ALL could be a marker of more resistant disease.

DNA adducts in human and patas monkey maternal and fetal tissues induced by platinum drug chemotherapy

Platinum-DNA adducts in placenta and blood from a woman exposed to 200 mg/m2 of cis-diamminedichloroplatinum(II) (cisplatin) and 300 mg/m2 diamminecyclobutanedicarboxylatoplatinum(II) (carboplatin) for ovarian cancer have been documented by cisplatin-DNA enzyme-linked immunosorbent assay (ELISA) and atomic absorbance spectrometry (AAS). A patas monkey model was used to investigate transplacentally induced cisplatin-DNA damage in fetal tissues. During the last trimester of gestation, 5 patas monkeys were given multiple doses of cisplatin to mimic human ovarian cancer treatment. In spite of careful choice of dose and treatment conditions, cumulative toxicity occurred in monkeys given doses comparable on a mg/m2 basis to those received by the human. A total dose of 12 mg/m2 (0.625 mg/kg body weight), given in the last trimester, supported fetal viability, and multiple tissues, taken by cesarean section, were examined in the fetal monkeys. By cisplatin-DNA ELISA and AAS, maternal tissues from the monkey receiving the highest dose contained approximately twice as much DNA damage as the fetal tissues. A similar relationship was observed when we compared DNA adduct formation in fetal liver and biopsies of liver taken from the monkey dams at cesarean delivery. In all of the monkey pairs studied there were very significant levels of DNA damage in the placenta, and high adduct levels in brains of fetuses that survived treatment. Thus, cisplatin does cross the placenta in the patas monkey. These observations imply that the human fetus, for which the total maternal dose was approximately 5.4 mg platinum drug/kg body weight, may also have sustained some DNA damage.

Suppression of in vivo clearance of N-nitrosodimethylamine in mice by cotreatment with ethanol

Oral cotreatment of mice with ethanol results in increased tumors in extrahepatic organs caused by some nitrosamines. This action, attributed in part to inhibition of hepatic first-pass carcinogen metabolism by ethanol, has possible relevance to the enhancing effect of alcoholic beverage consumption on human cancer risk. In this study, the effects of ethanol on clearance of N-nitrosodimethylamine (NDMA) were quantified in Swiss female and strain A male mice. In Swiss mice, a 1.6 g/kg ig ethanol dose preceding 1 or 5 mg/kg iv NDMA resulted in 20- to 30-fold increases in area-under-the-blood-concentration-vs.-time curves, mean residence times, and clearance half-times, and similar decreases in clearance. For a 0.5 mg/kg ig NDMA dose, the pharmacokinetic parameters were altered 30-fold and 450-fold by simultaneous ethanol doses of 0.08 and 0.8 g/kg, respectively. With 5 mg NDMA/kg ig, 0.4, 0.8, and 1.6 g/kg ethanol resulted in 6-, 10-, and 20-fold changes in clearance parameters. Comparison of the data with results obtained previously with patas monkeys indicated comparable effects of ethanol on tissue exposure to NDMA in the two species, confirming potential human applicability. In experiments with strain A mice, NDMA concentrations were also monitored in lung and liver. NDMA amounts in lung paralleled those in blood, and were more than sufficient to account for the previously reported increases in DNA adducts and tumors in lungs of similarly treated strain A mice.

Specific induction of hepatic cytochrome P4501a-2 in C57BL/6 and DBA/2 mice treated with 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)

The food mutagen/carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) is activated by cytochrome p4501a-2 via N-hydroxylation; various P450s may contribute to detoxification via ring hydroxylation. Alterations in P450 levels by IQ treatment might therefore influence its toxicity. To examine the role of Ah locus genotype on the biochemical effects of IQ, C57BL/6 (AhbAhb; p450Ia-1/2 inducible) and DBA/2 (AhdAhd, noninducible) mice of both sexes were given IQ at varying doses, with different vehicles and routes of administration. Livers taken after 24 hours were assessed for total cytochrome p450 and activities of ethoxyresorufin-O-deethylase (EROD, a p4501a-1 activity, inducible in Ahb mice), methoxyresorufin-O-demethylase (MROD, a p4501a-2 activity), and benzyloxyresorufin-O-dealkylase (BzROD, an activity of p4502b). There was little effect on total cytochrome p450, but all three enzyme activities were often induced, a maximum of 2.5-fold, in both sexes and in DBA/2 as well as C57BL/6 mice. However, Western immunoblot analysis with monoclonal antibodies demonstrated an increase only in p4501a-2 protein. p4501a-1 remained undetectable. A monoclonal antibody to p4502-b recognized one protein band in liver microsomes from males and two bands in female mice of both strains. Amounts of these proteins were not altered by IQ treatment. Thus, IQ specifically, if moderately, induces its activating enzyme, p4501a-2, in a process that was not clearly related to Ah responsiveness.

Transplacental carcinogenicity of cisplatin: initiation of skin tumors and induction of other preneoplastic and neoplastic lesions in SENCAR mice

cis-Dichlorodiammineplatinum (cis-DDP), an anticancer agent sometimes used in pregnant women for the treatment of malignant ovarian and uterine tumors, was tested for transplacental carcinogenic and/or tumor-initiating effects in SENCAR mice. Pregnant mice were given a single i.p. injection of either cis-DDP (7.5 mg/kg body weight) in 2.5% NaCl or the same weight-adjusted volume of NaCl (5 ml/kg body weight) on day 17 of gestation. Offspring were delivered and raised by their natural mothers until weaning at 3 weeks of age. Starting at week 4, offspring in experimental groups received topical applications of 2 micrograms 12-O-tetradecanoylphorbol-13-acetate (TPA) in acetone twice a week for 20 weeks while those in control groups received only acetone (0.2 ml/application) for the same duration. The experiment was terminated at 25 weeks of age. A high incidence (18 of 37; 48.7%) of papillomas was observed in offspring exposed transplacentally to cis-DDP and postnatally to TPA, while only 10% (4 of 40) of offspring exposed to TPA alone developed such tumors (P < 0.0002). Although no skin tumors were observed without TPA promotion, transplacental administration of cis-DDP resulted in development of thymic lymphomas, lung tumors, and proliferative kidney lesions in offspring. These results provide the first evidence that cis-DDP can initiate and/or induce preneoplastic and neoplastic lesions in multiple tissues transplacentally.

Low frequency of H-ras activation in naturally occurring hepatocellular tumors of C3H/HeNCr mice

Previous reports from several laboratories have consistently shown that approximately 30% of spontaneous hepatocellular adenomas and 70-80% of spontaneous hepatocellular carcinomas found in aged B6C3F1 [C57BL/6 (liver tumor resistant) x C3H (liver tumor susceptible)] male mice contain one of three missense point mutations in codon 61 of the H-ras oncogene, CAA-->AAA, CGA or CTA. Irrespective of subline, the C3H mouse, the paternal parent strain of the B6C3F1 hybrid, is more susceptible to spontaneous liver tumorigenesis than the B6C3F1 mouse. However, the role of H-ras in the pathogenesis of hepatocellular tumors in C3H mice is less clear, as widely different frequencies of activation of this gene, but by the same point mutations in codon 61, have been reported by various laboratories. The present study was undertaken to characterize H-ras involvement in hepatocellular tumors of aged C3H/He mice from the NCI-Frederick Cancer Research and Development Center Colony (C3H/HeNCr). Oncogene activation was evaluated in 45 C3H/HeNCr hepatocellular tumors by the NIH 3T3 transfection assays, and point mutations in the H-ras oncogene were detected and characterized in DNA fragments amplified by PCR, using dot blot hybridization analysis with mutation-specific oligonucleotide probes and direct dideoxy sequencing of PCR products. The only transforming gene detected in these tumors by NIH 3T3 transfection was H-ras. Only 17% (1/6) of spontaneous carcinomas and 8% (3/39) of spontaneous adenomas contained transforming H-ras sequences, each with a point mutation in codon 61. In all four cases with H-ras mutations, mutated sequences comprised a minor fraction of total H-ras gene copies in DNA extracted from primary tumors. H-ras mutations thus appear to have arisen relatively late in the pathogenesis of the neoplasms. For comparison, sections of formalin-fixed, paraffin-embedded hepatocellular tumors that occurred in untreated B6C3F1 hybrid mice sired by C3H/HeNCr males were assayed for the same H-ras mutations by PCR and dot blot hybridization. Nine of 13 such tumors (4/6 carcinomas, 5/7 adenomas) were positive. The overall difference in frequency of H-ras codon 61 mutations in hepatocellular tumors in C3H/HeNCr (4/45) versus B6C3F1 (9/13) was highly significant (P = 0.000035, Fisher's exact test). These data indicate that point mutations in H-ras do not generally play a major or an initiating role in spontaneous hepatocarcinogenesis of inbred C3H/HeNCr mice and contrast with the high rate of ras mutations in liver tumors of the B6C3F1 hybrid.

Persistence, gestation stage-dependent formation and interrelationship of benzo[a]pyrene-induced DNA adducts in mothers, placentae and fetuses of Erythrocebus patas monkeys

Since DNA adducts have been detected in the placentae of pregnant women who smoke cigarettes, the importance of these adducts as biomarkers of fetal exposure and risk has been evaluated using a non-human primate as a model. Pregnant Erythrocebus patas monkeys on days 50, 100 or 150 of gestation (term = 160 +/- 5 days) were treated once with 5-50 mg/kg benzo[a]pyrene (B[a]P), p.o. Fetuses were removed by Cesarean section 1-50 days after treatment and analyzed for DNA adducts by the nuclease P1 version of the 32P-postlabeling method. B[a]P induced high levels of DNA adducts in all fetal organs, placentae and maternal livers in all three trimesters of gestation. DNA adduct levels were higher in mid-gestation compared to early and late gestation. The major adduct detected was 10 beta-(deoxyguanosin)-N2-yl-7 beta,8 alpha,9 alpha-trihydroxy-7,8,9,10- tetrahydro-B[a]P. The adduct levels in fetal tissues increased with B[a]P dose, but at a much lower rate than in placentae or maternal livers. Preference in binding to DNA of various fetal organs was more apparent in early gestation compared to late gestation and at lower doses compared to higher doses. During early gestation and at low doses, B[a]P produced a similar level of DNA adducts in fetal lung, fetal liver, maternal liver and placenta. Individual fetal organ adduct levels correlated significantly with placental adduct levels, indicating placental and/or maternal contribution to genotoxic injuries in fetuses. However, the slopes of linear regression lines of correlation analyses varied among organs and among gestation stages at treatment, indicating fetal contribution to its own genotoxic injuries. DNA adduct levels in fetal skin were the lowest of all fetal organs tested and less affected by gestational stages at time of treatment. In contrast, DNA adduct levels in fetal liver exhibited distinct gestation stage specificity with higher adduct levels attained during mid-gestation compared to other stages of gestation. Adduct levels decreased at a much faster rate during the first 10-15 days compared to 15-50 days after B[a]P treatment. However, 10% of DNA adducts persisted 50 days after treatment in all organs studied. Together, the results suggest that placental adduction accurately indicates fetal exposure. Toxicokinetics of B[a]P and its metabolites as well as maternal, placental and fetal competence in activation and deactivation of B[a]P may be critical determinants in overall fetal risk to genetic damage. Importantly, maximal sensitivity to transplacental DNA damage may be during mid-gestation.

Comparison of transplacental and neonatal initiation of mouse lung and liver tumors by N-nitrosodimethylamine (NDMA) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and promotability by a polychlorinated biphenyls mixture (Aroclor 1254)

We have previously shown a positive tumor-promoting effect of a single dose of Aroclor 1254 on lung and liver tumors initiated neonatally in the mouse by N-nitrosodimethylamine (NDMA). In this study, we have confirmed and extended this observation with NDMA and the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) given either transplacentally or postnatally, followed by a single dose of Aroclor 1254 on day 56. This polychlorinated biphenyl (PCB) mixture was an effective promoter of both lung and liver tumors; however, there were specific initiator and sex-related differences in this response. Aroclor administration significantly increased the incidence of lung tumors initiated transplacentally by NDMA or NNK in male mice. Neither nitrosamine initiated tumors transplacentally in females, but lung tumors initiated with NNK and liver tumors caused by NDMA in neonatal females were promoted by PCBs. Both liver and lung tumors initiated neonatally by NDMA in male animals, but not NNK-initiated tumors, were promoted by PCBs. These data confirm that PCBs are able to promote both NDMA- and NNK-initiated tumors, but with chemical-, sex- and age-dependent difference; this suggests influences of both quantitative and qualitative factors in susceptibility to tumor promotion.

Metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in the patas monkey: pharmacokinetics and characterization of glucuronide metabolites

The metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was examined in the patas monkey, in order to provide further information about NNK metabolic pathways in primates. Female patas monkeys were given i.v. injections of [5-3H]NNK, and metabolites in serum and urine were analyzed by HPLC. Metabolism by alpha-hydroxylation of NNK was rapid and extensive, and the products of this pathway, 4-hydroxy-4-(3-pyridyl)butyric acid and 4-oxo-4-(3-pyridyl) butyric acid, accounted for a relatively large proportion of serum and urinary metabolites at all time points. This is significant because the formation of these products is associated with modification of DNA by NNK. The other major metabolic pathway was carbonyl reduction to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), which detected both unconjugated and diastereomeric O-glucuronides. One of these glucuronides had been previously identified in rat urine, but the other diastereomer, which was the more prevalent of the two in serum and urine, had not been observed in studies of NNK metabolism in rodents. It was characterized by its spectral properties, by enzymatic hydrolysis to NNAL, and by derivatization of the released NNAL enantiomer with (R)-(+)-alpha-methylbenzylisocyanate. The two NNAL glucuronides accounted for 15-20% of the urinary metabolites in monkeys given 0.1 micrograms/kg NNK, which is similar to a smoker's dose, suggesting their use as dosimeters of NNK exposure in humans. Pharmacokinetic parameters were consistent with those observed in previous studies of nitrosamines, and varied predictably with body weight of five species. The results of this study have provided new insights relevant to assessing human metabolism of NNK.

Enhancement of tumorigenesis by N-nitrosodiethylamine, N-nitrosopyrrolidine and N6-(methylnitroso)-adenosine by ethanol

Inclusion of 10% ethanol with 6.8 ppm N-nitrosodiethylamine in the drinking water of strain A male mice resulted in a 4-fold enhancement of multiplicity of lung tumors and a 16-fold increase in incidence of fore-stomach tumors, compared with carcinogen alone. Given with 40 ppm N-nitrosopyrrolidine, ethanol caused a 5.5-fold increase in lung tumor multiplicity. The inclusion of 15% ethanol with N6-(methylnitroso)adenosine, given orally to Swiss female mice, led to reduced body weights and shortened survival time related to hemangiosarcoma occurrence or increased incidence of thymic lymphoma, depending on dose of carcinogen. The data provide additional support for the proposal that co-administered ethanol increases the tumorigenicity of nitrosamines by blocking hepatic first-pass clearance.

Selective retention of polychlorinated biphenyl congeners in lung and liver after single-dose exposure of infant mice to Aroclor 1254

Infant male Swiss mice (8 days old) were given a single i.p. injection of 500 mg/kg of the polychlorinated biphenyl (PCB) mixture, Aroclor 1254, a treatment found in previous studies to result in promotion of nitrosamine-initiated lung and liver tumors. The amounts of the nine congeners that account for > 90% of the PCBs still present 1 day after treatment were quantified in liver, lung, and remainder of carcass 1, 7, 56, 84, and 112 days after treatment. Rates of decrease (half-times, dt1/2s) for total PCB concentration and for individual congeners were compared within and between compartments and with body weight doubling time. In carcass (adipose compartment) there was net loss beyond that expected from dilution due to growth, with the predicted lower dt1/2s for the more metabolizable congeners. By contrast, in lung, after a rapid loss during the 1st week, all congeners except for #153 (2,2'4,4'5,5'-hexachlorobiphenyl [HCB]) were retained and decreased in amount only as a function of dilution due to growth. One result was that congeners #105 (2,3,3',4,4'-pentachlorobiphenyl [PeCB]) and #138 (2,2',3,4,4',5'-HCB) constituted a higher proportion in lung than in carcass. A complex pattern was observed in liver: relative to carcass, there was retention of all congeners during the prepubertal growth phase, again with specific enrichment of #105, followed by more rapid depletion of certain congeners later. PCB-binding proteins and changes in lipid composition may contribute to these phenomena, which are of human relevance in that these congeners are commonly found in human serum and adipose samples.

The synergistic effects of cyclosporine and endothelin--demonstration of an important cardiodepressor action

Cyclosporine represents the foundation for current immunosuppressive therapy following solid organ transplantation. CsA use is associated with renal insufficiency and systemic hypertension. We hypothesized that CsA would enhance the vascular actions of endothelin (ET). Three groups of anesthesized dogs (n = 15) were studied. Group 1 received CsA alone (1 mg/kg), group 2 received ET alone (1 ng/kg/min), and group 3 received combined CsA (1 mg/kg) and ET (1 ng/kg/min). The hemodynamic and renal effects were evaluated after 30 min. Combined treatment resulted in a profound reduction in mean arterial pressure (-62 +/- 14 mmHg (P < .05) and cardiac output (-2.2 +/- 0.4.1/min (P < .05). The reduction in mean arterial pressure and cardiac output were significantly greater than that observed with CsA or ET alone. Systemic vascular resistance was not significantly changed. Combined CsA and ET resulted in a significant reduction in renal blood flow (195 +/- 18 to 101 +/- 11 ml/mm P < .05) but without evidence of active renal vasoconstriction. The decline in GFR (31.8 +/- 5.6 ml/min to being unmeasurable) was of greater magnitude than the change in renal blood flow, suggesting enhanced afferent anteriolar vasoconstriction or an alteration in the ultrafiltration coefficient. These studies demonstrate an important and synergistic cardiodepressor effect when CsA and ET are combined.

Characterization of ethanol's enhancement of tumorigenesis by N-nitrosodimethylamine in mice

The concentration-, time- and route-dependent effects of ethanol co-administration on tumorigenesis by N-nitrosodimethylamine (NDMA) were characterized in strain A male mice. With drinking-water administration, 1% ethanol was as effective as 5 or 10% in effecting a 4-fold enhancement of lung tumorigenesis by 5 p.p.m. NDMA. In a study of cumulative effects over time, 10% ethanol given with 1 p.p.m. NDMA resulted in a progressive increase in lung tumors from 16 to 72 weeks. In addition, at 72 weeks, the ethanol co-treatment resulted in a significant increase in kidney adenomas and possibly in vascular tumors of liver. A single i.g. dose of 5 mg/kg NDMA was significantly tumorigenic for lung, and the effect was dose-dependently increased by inclusion of ethanol, for up to a 9-fold enhancement with 20% ethanol. When 10% ethanol was given in the drinking water while NDMA was administered as 20 1 mg/kg doses by other routes--i.g., i.p., s.c. or i.v.--the ethanol treatment was without effect on lung tumor numbers. Collectively, the results provide strong support for inhibition of hepatic first-pass clearance of NDMA by cytochrome P450 2E1 as the mechanism of ethanol's effect, and suggest that several other possible mechanisms are unlikely. They also illustrate that a moderate dose of ethanol cumulatively increases tumor risk from a low dose of NDMA given over most of the lifetime of the animal.

Managing volunteers

In summary, non-profit organizations are often blessed with an abundance of enthusiastic and talented volunteers. However, to use volunteers effectively, development directors must be diplomatic, highly skilled and very well-organized. They must also understand the unique aspects of managing volunteers. The effective management of volunteers can ensure success for a non-profit organization and bring great satisfaction to volunteers who will work their hearts out for causes and organizations they believe in.

Persistent effects of a single dose of Aroclor 1254 on cytochromes P450IA1 and IIB1 in mouse lung

The polychlorinated biphenyl mixture Aroclor 1254 has been shown to elicit prolonged biochemical responses in several rodent species, particularly induction of mixed function oxygenases in hepatic tissue. Lung is also of interest since a single dose of Aroclor 1254 has been demonstrated to have a tumor promoting effect, increasing the numbers of lung tumors in Swiss mice initiated with N-nitrosodimethylamine. To investigate the enzyme induction response in lung, male Swiss mice were given a single 100 or 500 mg/kg dose of Aroclor 1254 and euthanized at time intervals ranging from 48 hr to 30 weeks. Both cytochromes P450IA1 and IIB1 were followed by use of specific enzyme activities and Western immunoblotting. The IA1 isoform, as quantified by ethoxyresorufin-O-deethylase activity and immunoblotting with monoclonal antibody 1-7-1, was significantly elevated for 30 weeks after both doses. In contrast, benzyloxy-resorufin-O-dealkylase activity (P450IIB1 specific), which is constitutively expressed in rodent lung, was unaffected by Aroclor treatment at the lower dose at early time points, but induced twofold at 30 weeks. At the higher dose, however, enzymatic activity was decreased to 50% of control values, an effect which persisted for 4 weeks postexposure. These changes were confirmed by Western immunoblotting utilizing monoclonal antibody 2-66-3. Concomitantly, content of individual PCB congeners in lungs and carcass was quantified by gas chromatography with electron capture detection. One congener, 2,3,3',4,4'-pentachlorobiphenyl, was selectively retained in lung compared to carcass. Lack of correlation between changes in lung content of PCBs and levels of the P450 isoforms suggested interactions between congeners in control of P450 induction and repression. These data confirm a prolonged P450 induction response in nonhepatic tissue following Aroclor exposure, and further suggest a bidirectional role for certain PCB congeners in the regulation of P450IA1 and P450IIB1 expression in lung tissue.

Reduced blood clearance and increased urinary excretion of N-nitrosodimethylamine in patas monkeys exposed to ethanol or isopropyl alcohol

Low concentrations of N-nitrosodimethylamine are metabolized in rodent and human liver by cytochrome P450IIE1, an activity competitively inhibitable by ethanol. In rodents coadministration of ethanol with N-nitrosodimethylamine results in increased tumorigenicity in extrahepatic organs, probably as a result of reduced hepatic clearance. To test this concept in a primate, the effects of ethanol cotreatment on the pharmacokinetics of N-nitrosodimethylamine were measured in male patas monkeys. Ethanol, 1.2 g/kg given p.o. before i.v. N-nitrosodimethylamine (1 mg/kg) or concurrently with an intragastric dose resulted in a 10-50-fold increase in the area under the blood concentration versus time curves and a 4-13-fold increase in mean residence times for N-nitrosodimethylamine. Isopropyl alcohol, 3.2 g/kg 24 h before N-nitrosodimethylamine, also increased these parameters 7-10-fold; this effect was associated with persistence of isopropyl alcohol and its metabolic product acetone, both IIE1 inhibitors, in the blood. While no N-nitrosodimethylamine was detected in expired air, trace amounts were found in urine. Ethanol and isopropyl alcohol pretreatment increased the maximum urinary N-nitrosodimethylamine concentration 15-50-fold and the percentage of the dose excreted in the urine by 100-800-fold. Thus ethanol and isopropyl alcohol greatly increase systemic exposure of extrahepatic organs to N-nitrosodimethylamine in a primate.

Distribution of cytochrome CYP2E1 in murine liver after ethanol and acetone administration

The effects of acetone and ethanol administration on cytochrome CYP2E1 in murine liver were investigated. A monoclonal antibody (Mab 1-98-1) specific to rat ethanol-inducible P450 recognized a major band of Mr 51,000 in Western immunoblots of mouse liver microsomes. This band was increased 1.8-fold by 10% ethanol in drinking water for 2 weeks, 4.7-fold by 1% acetone in drinking water for 1 week, and 2.5-, 2.1- and 6.8-fold by ethanol in a liquid diet for 9 days, 2 weeks and 3 weeks respectively. Immunohistochemical staining experiments with the same antibody showed specific localization in centrilobular regions of liver lobules, with variations in intensity that corresponded to differences detected in Western immunoblots. Uniform cellular increases in centrilobular staining occurred with all ethanol treatments, whereas a more heterogeneous increase in individual cells was noted after acetone. Lipid accumulation in hepatocytes was pronounced after 3 weeks on the ethanol liquid diet but was less so in other treatment groups, and thus did not consistently correlate with enzyme induction. Microsomal aniline p-hydroxylase activity was also induced by the acetone and ethanol treatments, with a progressive increase from 9 days to 3 weeks on the ethanol liquid diet. Changes in this activity in general paralleled those found with immunohistochemistry and immunoblotting. The results demonstrate that (i) the mouse is a good model for correlative biochemical and histochemical studies of CYP2E1 induction, (ii) in the mouse liver, this P450 is preferentially localized in centrilobular regions constitutively as well as in induced states, (iii) the centrilobular pattern varies under different induction conditions, and (iv) there is a progressive inductive increase in CYP2E1 protein and enzyme activity with chronic ethanol treatment over at least 3 weeks.