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Biomedical subjects

K Randerath

Publications and source records attributed to K Randerath.

At least 109 records · Page 6Linked to original sources
PubMed1989

Age-dependent covalent DNA alterations (I-compounds) in rodent tissues: species, tissue and sex specificities.

I-compounds are non-polar covalent DNA modifications of as yet undetermined structure that tend to accumulate in an age-dependent manner in tissues of untreated animals. They are detectable by 32P-postlabeling assay because of their adduct-like properties and chromatographically resemble DNA nucleotides containing bulky/hydrophobic moieties. To determine which factors may be involved in their formation, I-compounds were examined by 32P-postlabeling in liver and kidney DNA of female and male Sprague-Dawley rats and Syrian hamsters of different ages (1, 4 and 10 months and 1, 2.5 and 9.5 months, respectively). The following results were obtained: (i) Every tissue DNA studied contained characteristic I-compounds. (ii) Patterns and amounts of I-compounds were reproducible among animals of the same kind. (iii) There were pronounced organ and species differences. (iv) I-compound patterns were sex-dependent. (v) I-compound levels increased with age in all tissues studied, except in male hamster kidney, a target organ of estrogen-induced carcinogenesis. The highest levels were observed in liver and kidney of 10-month-old female rats. (vi) The rise of I-compound levels was less steep during the later part of the observation period for female but not male animals. (vii) Gonadectomy decreased I-compound levels in female hamster kidney DNA, while causing a slight increase in male animals later in life. These I-compounds were identical to previously reported DNA modifications that increased in male hamster kidneys after prolonged estrogen treatment. Points, iv, vi and vii strongly implicated sex hormones in I-compound formation. The qualitative effects of species, tissue differentiation, gender and sex hormones on these DNA modifications support the hypothesis that I-compounds are formed by the binding of endogenous electrophiles to DNA. As persistent DNA alterations, they are likely to affect DNA replication and to play a role in spontaneous and chemically induced carcinogenesis and in aging.

Aging↗
PubMed1989

Reduced accumulation of I-compounds in liver DNA of rats fed a choline-devoid diet.

Groups of rats were fed for 1, 4 or 7 months choline-devoid or choline-supplemented diets, that provided approximately 50% of the methionine, and 0.15% or 150% of the choline requirements of young, growing rats. Liver DNA was isolated and analyzed by the nuclease P1-enhanced version of the 32P-postlabeling assay, which detects aromatic/hydrophobic DNA adducts and I-compounds (adduct-like DNA modifications shown to accumulate in tissue of aging rats). DNA adducts and qualitative differences in the patterns of I-compounds were not observed in rats fed the two diets. However, in rats fed the choline-devoid diet there was a drastic reduction in the accumulation of I-compounds, compared with that in rats fed the control diet. These results extend previous evidence of a lack of relevant DNA adducts in the liver of rats fed the choline-devoid diet, and suggest the possibility of a role of I-compounds in the carcinogenicity of this diet.

Animals↗
PubMed1989

A new sensitive 32P-postlabeling assay based on the specific enzymatic conversion of bulky DNA lesions to radiolabeled dinucleotides and nucleoside 5'-monophosphates.

A new sensitive 32P-postlabeling assay for DNA adducts has been developed in which DNA is hydrolyzed initially by nuclease P1 and prostatic acid phosphatase instead of micrococcal nuclease and spleen phosphodiesterase as employed in previous postlabeling procedures. When DNA containing bulky adducts, X1, X2, .....Xn, is digested with nuclease P1 at pH 5, normal nucleotides are released as 5'-monophosphates, pN, while adducts are excised as 5'-phosphorylated dinucleotides, pXipN, because internucleotide linkages on the 3' side of X resist attack by nuclease P1. Addition of prostatic acid phosphatase to such a digest results in 5'-dephosphorylation of the nucleotides to normal nucleosides, N, and adducted dinucleotides, XipN, carrying a 5'-terminal free hydroxyl group. The dinucleotides but not nucleosides are converted to 5'-32P-labeled dinucleotides, [32P]pXipN, by T4 polynucleotide kinase-catalyzed [32P]phosphate transfer from [gamma-32P]ATP. Upon mapping on polyethyleneimine--cellulose anion-exchange TLC, the labeled dinucleotide adducts produce characteristic autoradiographic fingerprints. Alternatively, they are further digested with snake venom phosphodiesterase to yield 5'-monophosphates, [32P]pXi and pN. TLC profiles of the monophosphate adducts are distinct from those of the dinucleotides. These reactions provide the basis of the new 32P-postlabeling scheme, which is compared in this paper with a previously reported protocol yielding adducts in the form of 5'-32P-labeled 3',5'-bisphosphates, [32P]pXip. The results show that the availability of three different types of 32P-postlabeled derivatives for the same adduct aids in the analysis and chromatographic characterization of DNA adducts from diverse exogenous and endogenous sources.

Acid Phosphatase↗
PubMed1989

Use of the 32P-postlabelling assay to study transplacental carcinogens and transplacental carcinogenesis.

The formation of DNA adducts represents a key step in the postnatal initiation of the carcinogenic process. Little is known as yet about the role of prenatally induced adducts in transplacental carcinogenesis in offspring. Measurement of transplacental DNA damage in fetal organs of experimental animals has been difficult in the past because of the small amounts of DNA available and low adduct levels. In principle, these difficulties have been overcome by the recent development of a highly sensitive 32P-postlabelling assay which can be applied to a large number of DNA adducts of diverse structure and requires only microgram amounts of DNA for analysis. In this assay, tissue DNA is degraded to mononucleotides; these are enzymatically 32P-labelled via T4 polynucleotide kinase-catalysed [32P]phosphate transfer from [gamma--32P]ATP, to form 5'--32P-labelled 3',5'-bisphosphate derivatives; the labelled products are separated into normal and adducted [32P]nucleotides and quantified by thin-layer chromatography, autoradiography and scintillation (Cerenkov) counting. This technique allows the detection and quantitation of one adduct in 10(8)-10(10) DNA nucleotides (approximately 1-100 adducts/mammalian genome) using a 10-micrograms DNA sample and has been applied in studies of adduct formation from transplacental carcinogens in fetal and adult rodent tissues. In this paper, we review application of 32P-postlabelling to DNA adducts formed with transplacental or suspected transplacental carcinogens in fetal and maternal tissues. The carcinogens studied include diethylstilboestrol (DES), benzo[a]pyrene, safrole, 4-aminobiphenyl and 4-nitroquinoline-1-oxide, as well as cigarette smoke condensate. In DNA of DES-exposed hamsters, one major and several minor adduct spots were observed, which were absent from vehicle controls. A characteristic adduct, which resembled the major hamster adduct chromatographically, was detected in all exposed mouse tissue, except fetal kidney. Chronic administration of low doses of DES to male Syrian hamsters led to an entirely different pattern of adducts in kidney DNA, the target organ of carcinogenesis. These adducts did not contain covalently bound oestrogen moieties and appeared to be formed indirectly: oestrogen appeared to induce or enhance the synthesis of an endogenous electrophilic metabolite reacting with DNA. Thus, multiple mechanisms exist by which DES can damage DNA. Additional work using 32P-postlabelling has shown that non-hormonal genotoxicants (e.g., benzo[a]pyrene, safrole, 4-aminobiphenyl, 4-nitroquinoline-1-oxide) and cigarette smoke condensate given to pregnant mice can induce specific DNA adduct profiles in fetal tissues.(ABSTRACT TRUNCATED AT 400 WORDS)

4-Nitroquinoline-1-oxide↗
PubMed1988

DNA adduct formation of the carcinogen 2-amino-3-methylimidazo[4,5-f]-quinoline in target tissues of the F-344 rat.

2-Amino-3-methylimidazo[4,5-f]quinoline (IQ), a potent bacterial mutagen present in broiled sardines, cooked beef and beef extract, is a carcinogen in the F-344 rat, affecting mainly the liver and small and large intestines. Using 32P-postlabeling assays, the formation of IQ-DNA adducts was examined in male F-344 rats. Twenty-four hours after i.p. doses (5-50 mg IQ/kg) the liver, small and large intestine each showed the presence of 5 adducts, the liver and large intestine having an average of 18.1 and 2.4 times as many adducts, respectively, as the small intestine. None of these adducts could be detected in vehicle-treated animals. It is concluded that IQ forms specific DNA adducts in target tissues of the F-344 rat.

Animals↗
PubMed1988

Quantitative associations between DNA damage in human placenta and maternal smoking and birth weight.

Specimens of human placental DNA were tested for chemical addition products (adducts) by recently developed 32P-postlabeling and immunologic assays, and results were compared with data concerning maternal exposures and birth weight. A total of 7 different adducts were detected in the 53 specimens of human placental tissue examined by the 32P-postlabeling assay. Three of these adducts were found almost exclusively in smokers. Among smokers there were positive dose-response relationships between levels of the smoking-related adducts and biochemical estimates of doses of maternal exposure to cigarette smoke during pregnancy. Levels of 1 adduct found only in smokers appeared to relate directly to amounts of caffeine consumption by the mother. In addition to these relationships with maternal exposures, levels of smoking-related adducts were inversely associated with the birth weight of offspring. Results from this study suggest that even at their current formative stage of development, assays for DNA adducts may help identify determinants of DNA damage to human tissues and improve our ability to demonstrate dose-response relationships for the effects of environmental exposures to potentially carcinogenic agents.

Adult↗
PubMed1988

Inhibition of estrogen-induced renal carcinogenesis in male Syrian hamsters by tamoxifen without decrease in DNA adduct levels.

Estrogens have previously been shown to induce covalent DNA modifications specifically in the hamster kidney, the target organ of estrogen-inducible and -dependent renal carcinoma. The DNA adducts, formed by yet unknown mechanisms, have been postulated to mediate hormonal carcinogenesis in this animal model. In an attempt to study a possible involvement of estrogen receptor mechanisms in the formation of DNA adducts, 17 beta-estradiol and the antihormone tamoxifen were concomitantly administered as s.c. implants to male Syrian hamsters. 17 beta-Estradiol-treated and tamoxifen-treated animals served as positive and negative controls, respectively. The tumor incidence decreased from 100% in 17 beta-estradiol-treated controls to 25% in the group receiving tamoxifen in addition to hormone. Tamoxifen-treated animals did not develop kidney tumors and did not show any detectable DNA damage. DNA adduct levels were comparable in hamsters treated with 17 beta-estradiol and 17 beta-estradiol plus tamoxifen for 5 or 7 months. In hamsters inoculated with H-301 cells, which are derived from the estrogen-induced hamster renal carcinoma and are estrogen dependent for growth, tamoxifen decreased estrogen-dependent H-301 tumor growth. However, in cell culture, neither 17 beta-estradiol nor tamoxifen influenced H-301 cell division. It was concluded that tamoxifen inhibited the growth of estrogen-induced renal carcinoma but did not interfere with tumor initiation since it did not inhibit the formation of DNA adducts. Moreover, receptor mechanisms were most probably not involved in the induction of DNA modifications by estrogens.

Animals↗
PubMed1988

Role of metabolism and DNA adduct formation in the induction of sister chromatid exchanges in human lymphocytes by diethylstilbestrol.

Recent studies have shown that diethylstilbestrol (DES) induces sister chromatid exchanges (SCEs) in lymphocytes from pregnant and premenopausal women but has only a slight effect on lymphocytes from post-menopausal women or men. In this study blood specimens from premenopausal women were used to define the role of different metabolic pathways on DES-induced formation of SCEs and to determine whether conditions resulting in induction of SCEs also induced detectable levels of DNA adducts. Exposure of lymphocytes in vitro to 0-40 microM DES induced a concentration-dependent increase in SCEs. Addition of indomethacin to the cultures partially abolished DES-induced SCEs, suggesting involvement of prostaglandin synthetases in the formation of specific DES metabolites that cause SCEs. alpha-Naphthoflavone, an inhibitor of cytochrome P-450 monooxygenases, had no effect on DES-induced SCEs. Cells exposed to DES at doses sufficient to cause large increases in SCE induction did not have adducts detectable by a 32P-postlabeling assay capable of revealing adducts at a level of 1 adduct/10(9) normal nucleotides.

Benzoflavones↗
PubMed1988

Tissue distribution of covalent DNA damage in mice treated dermally with cigarette 'tar': preference for lung and heart DNA.

The high incidence of lung cancer in smokers is thought to be related to the direct exposure of bronchial and pulmonary cells to carcinogens in inhaled cigarette smoke. Using a 32P-postlabeling assay for chemically induced covalent DNA alterations, we found that unfractionated, relatively non-polar cigarette smoke components bound preferentially to lung and heart DNA in female ICR mice. After 6 days of topical treatment with cigarette smoke condensate (CSC) equivalent to a total of 4.5 cigarettes, covalent DNA damages was estimated to be 6.2, 5.7, 3.9 and 1.9 times higher, respectively, in lung, heart, skin and kidney than in liver, ranging from approximately 1 adduct in 5.4 +/- 0.7 X 10(6) DNA nucleotides in lung to 1 adduct in 3.3 +/- 0.6 X 10(7) DNA nucleotides in liver. Spleen DNA was virtually adduct-free. Adducts occupied two extensive zones, designated diagonal radioactive zone (DRZ) 1 and DRZ 2, on TLC fingerprints. Preference for lung and heart DNA was also observed in mice treated for 1 or 3 days. An inverse association appeared to exist between the tissue distribution of CSC-induced covalent DNA damage and the reported activity of enzymes catalyzing the metabolism of xenobiotics (cytochrome P-450 monooxygenases, phase II enzymes) and toxic oxygen species (superoxide dismutase, catalase). The results suggest that the well-known pulmonary and cardiovascular organotropism of cigarette-smoking-associated adverse health effects may, in part, have its origin in the inherent capacity of cigarette smoke components to induce lesions in lung and heart DNA in a tissue-specific manner. Possible mechanisms and health implications of the preferential binding of presumably aromatic CSC constituents to lung and heart DNA are discussed.

Administration, Topical↗
PubMed1988

A comparison between different types of covalent DNA modifications (I-compounds, persistent carcinogen adducts and 5-methylcytosine) in regenerating rat liver.

I-Compounds have been recently identified as adduct-like nonpolar covalent DNA modifications that are detectable by 32P-postlabeling assay in tissues of untreated experimental animals and increase with age. Additional I-compounds have now been observed in liver DNA of male Sprague-Dawley rats when the chromatographic conditions were modified to allow for the detection of more polar adducts exhibiting low affinity to polyethyleneimine (PEI)--cellulose anion-exchange thin-layer material. The total I-compound level in 10-month-old animals was as high as one modification in approximately 10(7) nucleotides. This represented a minimum estimate since 100% recovery of all rat liver I-compounds in 32P-labeled form presumably was not achieved by the procedures used. The I-compound pattern was reproducible and variation of I-compound levels among individual animals of the same age was small. We have used regenerating rat liver herein as a model to compare the properties of I-compounds with those of persistent 2-acetylaminofluorene (AAF)-induced DNA adducts and of 5-methylcytosine (m5C), a normal enzymatic DNA modification. Eight- to 10-month-old male Sprague-Dawley rats were given 2-AAF (50 mg/kg in DMSO) or vehicle (DMSO) by i.p. injection. Partial hepatectomy was performed 6 weeks later (i.e. after AAF adduct levels had stabilized) and regenerating liver samples were taken 1 week after the operation for DNA analysis. Consistent with the restoration of cell and tissue loss, the overall levels of I-compounds and 2-AAF adducts were reduced to approximately 47% and approximately 45% respectively of control in regenerating liver by dilution with newly synthesized DNA, while the m5C level was not affected. Thus, in regenerating liver, I-compounds resembled carcinogen--DNA adducts and not m5C. This supports our hypothesis that the formation of these DNA modifications may be due to the binding to DNA of small amounts of reactive electrophilic by-products of normal metabolic activities, leading to the slow accumulation of I-compounds in tissue DNA with ageing.

2-Acetylaminofluorene↗
PubMed1988

Organ-specific effects of long term feeding of 2,3,7,8-tetrachlorodibenzo-p-dioxin and 1,2,3,7,8-pentachlorodibenzo-p-dioxin on I-compounds in hepatic and renal DNA of female Sprague-Dawley rats.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent hepatocarcinogen, and 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PCDD) on liver and kidney DNA of female Sprague-Dawley rats were investigated by 32P-post-labeling assay. The compounds were administered by gavage [1 microgram/kg/week in corn oil (5 ml/kg)] to the animals for up to 6 months. No exposure-related 32P-labeled spots indicative of TCDD or PCDD covalent DNA adducts were noted on the chromatograms of kidney or liver DNA nucleotides from the rats exposed to the toxins for 2 and 6 months. Corn-oil treated control animals exhibited the characteristic tissue- and age-specific patterns of 32P-labeled I-spots in liver and kidney DNA which are associated with specific DNA modifications of unknown origin and function. Treatment with either TCDD or PCDD resulted in a substantial reduction of the levels of I-compounds in liver, a target organ for TCDD carcinogenesis. After 6 months of exposure to TCDD the reductions in the amounts of individual hepatic I-compounds ranged from 37 to 77% and decreased levels were also observed after 2 months of treatment. It was apparent that PCDD was not as effective as TCDD in reducing hepatic I-compound levels and this corresponded with the lower aryl hydrocarbon receptor binding activity of the former compound. In contrast, TCDD and PCDD did not cause any significant decrease of I-compounds in the kidney which is not a site of TCDD-mediated carcinogenicity in female Sprague-Dawley rats. Whether I-compound deficiency contributes to TCDD-mediated hepatocarcinogenesis (e.g. by facilitating DNA replication) needs to be investigated.

Aging↗
PubMed1988

Comparison of 32P-postlabeling and high pressure liquid chromatographic analyses for 7,12-dimethylbenz[a]anthracene--DNA adducts.

[3H]7,12-Dimethylbenz[a]anthracene-modified DNA obtained from mouse cells in culture was enzymatically hydrolyzed to nucleoside 3'-phosphates, postlabeled with [32P]phosphate, and the carcinogen-modified nucleoside bisphosphates were separated by thin layer chromatography. Each adduct spot was eluted, dephosphorylated and the resulting [3H]nucleoside adducts were analyzed by high pressure liquid chromatography so that the structural information available for the liquid chromatographic peaks could be applied to the spots obtained from the postlabeling procedure. After this cross referencing, specific dihydrodiol epoxide-nucleotide adducts can now be monitored by the postlabeling technique.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Hypomethylation of DNA in estrogen-induced and -dependent hamster kidney tumors.

The development and maintenance of DNA hypomethylation were investigated in male Syrian hamsters during the course of induction of renal carcinoma by estrogens and in an estrogen-dependent tumor derived from H-301 cells. The H-301 cell line was obtained from a primary renal carcinoma induced by E-diethylstilbestrol treatment. Covalent DNA modifications in estrogen-exposed kidney and tumor tissues were also examined. The five tumors investigated were induced by s.c. estrogen treatment of animals for 7-9 months. Covalent DNA adducts were detected in kidneys after 5-7 months of exposure to various estrogens, but not in primary tumors induced by estrogen treatment for 7-9 months. Estrogen-induced covalent DNA modifications likewise were not detectable in tumors grown in estrogenized hamsters inoculated with H-301 cells. In contrast, DNA was hypomethylated in primary tumors induced by E-diethylstilbestrol, estradiol or 11 beta-ethyl-17 alpha-ethinyl estradiol, but not in untreated and estrogen-exposed kidney. Compared with kidney tissue, there was an 11-24% decrease in total genomic DNA methylation in the estrogen-induced and -dependent tumors. DNA hypomethylation was maintained in tumors derived from H-301 cells. Discontinuation of estrogen treatment rapidly decreased the size of estrogen-dependent H-301 tumors, but did not affect the degree of DNA hypomethylation. Thus, DNA hypomethylation occurred in hormone-dependent primary neoplasms and was maintained after serial transplantations independent of the growth status.

Animals↗
PubMed1988

Aromatic DNA adducts in white blood cells of foundry workers.

Blood samples were obtained from volunteers working in a Finnish iron foundry who were occupationally exposed to polycyclic aromatic hydrocarbons (PAH) and from control subjects not known to be occupationally exposed to this class of chemical carcinogens. Foundry workers were classified as belonging to high, medium or low exposure groups according to their exposure to airborne benzo[a]pyrene: high, greater than 0.2: medium, 0.05-0.2: low, less than 0.05 micrograms benzo[a]pyrene/m3 air). Aromatic adducts were found to be present in white blood cell DNA from most of the exposed workers using the enzyme-linked immunosorbent assay (ELISA) to detect aromatic DNA adducts and the 32P-postlabelling technique. There was a dose-response relationship between the estimated exposure and adduct levels by both methods, and a reasonable correlation between the results of the immunoassay and postlabelling carried out in two laboratories. The levels of adducts found in the samples from the high and medium exposure groups by ELISA ranged up to five adducts in 10(7) nucleotides: the aromatic adducts detected by the postlabeling assay were at a level of two adducts/10(8) nucleotides in the high and medium exposure categories. No effect due to age, sex or the smoking habits of the subjects was observed. The results indicate that DNA extracted from white blood cells of highly exposed workers is more likely to contain aromatic DNA adducts than that from workers without occupational exposure to PAH, but large interindividual variations were evident. This study suggests that the antibody and 32P-postlabelling assays may be useful in monitoring human exposure to known and previously unidentified environmental genotoxic agents.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1988

Monitoring human exposure to carcinogens by ultrasensitive postlabelling assays: application to unidentified genotoxicants.

The 32P-postlabelling assay is a recently developed analytical tool for the detection and measurement of nucleic acid (DNA and RNA) adducts formed by covalent binding of identified or unidentified electrophiles. The detection limit of the assay for many adducts is as low as 0.3 amol adduct/microgram DNA ( = one adduct/10(10) DNA nucleotides, or one adduct per mammalian genome). As presented here, the method can be applied to DNA alterations elicited by (i) complex mixtures of genotoxicants (e.g., cigarette smoke, occupational exposures), (ii) oestrogens (i.e., hormones that cause DNA damage via the formation of unidentified electrophiles), and (iii) DNA-reactive chemicals that may be formed metabolically in animal tissues without known exposure and give rise to adduct-like DNA alterations (termed I compounds).

Carcinogens, Environmental↗
PubMed1987

Correlation of aromatic hydroxylation of 11 beta-substituted estrogens with morphological transformation in vitro but not with in vivo tumor induction by these hormones.

In estrogen-induced cancer, catechol formation from administered steroids has been postulated to be a necessary event for estrogen activation and subsequent damage to cellular macromolecules. In the present study, this hypothesis has been tested using two homologous series of structurally related estrogens: estradiol, 11 beta-methylestradiol, 11 beta-ethylestradiol, 11 beta-methyl-17 alpha-ethinylestradiol, 11 beta-ethyl-17 alpha-ethinylestradiol, 11 beta-methoxy-17 alpha-ethinylestradiol, and 17 alpha-ethinylestradiol. In the Syrian hamster renal carcinoma model, only 11 beta-methylestradiol and 17 alpha-ethinylestradiol were weak carcinogens (2 of 20 and 2 of 24 hamsters with tumors, respectively). The other estrogens tested induced renal carcinoma within 6 to 9 months with an incidence in the 80-100% range. The tumor incidence in vivo did not correlate with the rates of catechol formation by hamster kidney microsomes in vitro. Compared to estradiol (relative rate, 100), catechol formation by the substituted estrogens was significantly lower, ranging from 48 (11 beta-methylestradiol) to 2 (11 beta-methoxy-17 alpha-ethinylestradiol). Kidney DNA of hamsters treated with the four 17 alpha-ethinyl estrogens, when analyzed by 32P postlabeling assay, contained the same set of covalently modified nucleotides the formation of which had previously been found to precede estrogen-induced renal carcinogenesis in vivo. In contrast, relative rates of catechol estrogen formation by BALB/c 3T3 microsomes correlated with induction of morphological transformation of BALB/c 3T3 cells and decreased in the following order: 11 beta-methylestradiol greater than 17 alpha-ethinylestradiol greater than or equal to estradiol greater than 11 beta-ethylestradiol greater than 11 beta-methoxy-17 alpha-ethinylestradiol. The hormonal potencies of several estrogen derivatives studied by various assays did not correlate with in vivo carcinogenic or in vitro cell-transforming activities. It is concluded from these experiments that in cell culture catechol formation and morphological transformation are directly related. In vivo, aromatic hydroxylation of administered estrogens did not correlate with the incidence of estrogen-induced renal carcinoma in Syrian hamsters.

Animals↗
PubMed1987

Localization of estrogen-induced DNA adducts and cytochrome P-450 activity at the site of renal carcinogenesis in the hamster kidney.

Renal carcinoma in male Syrian hamsters, induced by chronic administration of estradiol for 5-7 months, is known to arise in the cortex at the cortico-medullary junction. In this in vivo model for hormonal carcinogenesis, estrogen-induced covalent DNA adducts have previously been observed in whole kidney and have been postulated to be involved in tumor induction. In the present study, the intrarenal distribution of estrogen-induced DNA modification and estrogen metabolizing enzymes were investigated in male Syrian hamsters to ascertain a role of metabolism and adduct formation in estrogen-induced carcinogenesis. The highest estrogen-induced DNA adduct concentrations as measured by 32P-postlabeling analysis were found in the renal cortex of hamsters treated with estradiol for 7 months. Total adduct levels in medullary DNA were approximately one-half of those found in cortex. Cytochrome P-450 enzymes were detected only in microsomes of kidney cortex (approximately 0.8 +/- 0.6 nmol P-450/mg protein) but not medulla of untreated male Syrian hamsters. Prostaglandin endoperoxide synthase activity in kidney cortical microsomes was 1/5 of the activity found in medullary microsomes. Thus, microsomal cytochrome P-450 levels and estrogen-induced DNA adduct formation were highest in hamster kidney cortex, the origin of renal tumorigenesis. It is postulated that estrogen metabolism by cytochrome P-450 enzymes leading to covalent DNA modification plays a role in hormonal carcinogenesis in the hamster kidney.

Animals↗