Male Hamster Kidney Research Articles

Metabolic Deglucuronidation and Demethylation of Estrogen Conjugates as a Source of Parent Estrogens and Catecholestrogen Metabolites in Syrian Hamster Kidney, a Target Organ of Estrogen-Induced Tumorigenesis

Estrogen-induced tumors in kidneys of male Syrian hamsters have been postulated to arise from cells which are damaged by free radicals and other reactive species generated during metabolic redox cycling of catecholestrogens and which at the same time are exposed to excessive growth stimulation mediated by estrogen receptors. In this study, we have determined the rates of metabolic deconjugation of estrogen glucuronides and of catecholestrogen methyl ethers by cellular fractions from male hamster kidney and liver to evaluate the contribution of this process to renal pools of parent estrogens and of catecholestrogen metabolites. Lysosomes from male hamster kidney catalyzed the deconjugation of estradiol- and estrone-3β-D-glucuronides at rates of 51.7 and 64.6 pmol/mg protein/min, respectively, which were 65 and 34% higher than corresponding deconjugation rates by liver lysosomes. Treatment of hamsters with estradiol implants for 9 days increased lysosomal glucuronidase activities for these estrogen glucuronides by 15 to 25% in kidney and doubled the activities in liver, but it did not alter their correspondingKmvalues. Microsomal glucuronidase activities in kidney and liver were approximately 10 to 20% of lysosomal activities. Rates of demethylation of 2- and 4-methoxyestradiol by kidney microsomes were comparable (withVmaxvalues of 24 and 30 pmol/mg protein/min, respectively), whereas the rate of demethylation of 2-methoxyestradiol by liver microsomes was approximately fivefold higher than that of 4-methoxyestradiol. The rates of renal demethylation of methoxyestrogens were comparable with previously published rates of renal aromatic hydroxylation of estradiol, whereas rates of hepatic demethylation were about one-fifth of the corresponding hydroxylation rates. It is concluded that metabolic deconjugation is an important source of primary estrogens and of catecholestrogen metabolites in hamster kidney, a target of estrogen-induced tumorigenesis. The increased renal estrogen glucuronidase activity during prolonged estradiol treatment may also facilitate the development of estrogen-induced tumors in this target organ.

Induction of a DNA adduct detectable by 32P-postlabeling in the dorsolateral prostate of NBL/Cr rats treated with estradiol-17 beta and testosterone.

Treatment with estradiol-17 beta and testosterone induces epithelial dysplasia and, subsequently, adenocarcinoma in the dorsolateral prostate of NBL rats. The purpose of this study was to determine whether this carcinogenic effect is mediated by genotoxicity. Analogous to adducts produced by estrogens in the male hamster kidney, a target of estrogen carcinogenicity, induction of DNA adducts detectable by 32P-postlabeling was investigated in the prostate target tissue. NBL rats were treated with separate Silastic tubing implants containing testosterone and estradiol-17 beta. Control animals received empty implants. Animals were killed at 8, 16 and 24 weeks after initiation of treatment, and accessory sex glands were sampled for adduct analysis. DNA of the dorsolateral and ventral prostate and the coagulating gland (= anterior prostate) was isolated and analyzed by nuclease P1-enhancement of the 32P-post-labeling assay. DNA adducts were quantitated by Cerenkov counting. An adduct occurred selectively in DNA of the dorsolateral prostate of rats treated with estradiol plus testosterone for 16 or 24 weeks with relative adduct level values of approximately 10 x 10(9), but not in DNA of the ventral or anterior prostate. The adduct was not present in DNA of prostate tissue of rats treated for 8 weeks or in DNA of control tissues. This adduct was unique with respect to chromatographic location and has not been observed before in any tissue of control or hormone-treated animals. Neither the structure of the treatment-induced adduct nor the mechanism of its formation is known. However, the selective occurrence of this adduct in the tissue of origin of the carcinomas and its appearance coinciding with putative preneoplastic lesions and preceding carcinoma development suggests a causal relation between adduct formation and prostate cancer development in testosterone plus estradiol-17 beta-treated rats.

Metabolism of [4- 14C]estrone in hamster and rat hepatic and renal microsomes: Species-, sex- and age-specific differences

The metabolism of [4- 14C]estrone (E 1) was examined in liver and kidney microsomes of adult castrated male and ovariectomized female hamsters and rats and in neonatal and immature hamster renal microsomes. In castrated male hamster liver microsomes, E 1 was metabolized extensively to six major metabolites; 15β-hydroxyestrone, 7α-hydroxyestrone, 6α-hydroxyestrone, 6β-hydroxyestrone, 2-hydroxyestrone, and Δ(9,11)-dehydroestrone, and a nonpolar fraction. Six minor metabolites of E 1 were also detected. In contrast, kidney microsomes derived from castrated male hamsters metabolized E 1 to mainly 17β-estradiol, 2- and 4-hydroxyestrone, 6α-hydroxyestrone, 6β-hydroxyestrone and one monohydroxyestradiol metabolite. However, 16α-hydroxyestrone was not detected. A variable, but low amount of estriol was also found. Interestingly, the quantity of 2-hydroxyestrone found in kidney microsomes of the hamster represented 26% of the total amount of metabolites formed, whereas in liver microsomes, only 9% of the overall metabolism resulted in the formation of 2-hydroxyestrone. The ability of kidney microsomes of female ovariectomized hamsters and two different rat strains to metabolize E 1 was 5.9- and 9.4-fold lower, respectively, compared to renal microsomes of male castrated hamsters. The onset of oxidative metabolism in newborn hamster kidneys during development was also assessed. The results indicate that the oxidative metabolism of [ 14C]E 1 in renal microsomes of newborn hamsters was 20-fold less than in kidney microsomes of adult hamsters. While catechol E 1 metabolites were essentially negligible in hamster kidneys of these ages, it was evident that the conversion of E 1 to estradiol via 17β-hydroxysteroid dehydrogenase resembles levels seen in the adult animals. Between the age of one and two months, the male hamster kidney exhibited the capacity to metabolize E 1 at levels seen in fully mature adult hamsters.

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.

Metabolism and irreversible binding of diethylstilbestrol in the kidney of the Syrian golden hamster

Oxidative metabolism of [ 3H]diethylstilbestrol (DES) and the irreversible binding of reactive [ 3H]DES metabolites to the macromolecules in kidney slices of the Syrian golden hamster were investigated. Non-extractable binding of [ 3H]DES to kidney macromolecules was observed after incubating hamster kidney slices under aerobic conditions (95% O 2/5% CO 2), but not under anaerobic conditions (100% nitrogen + 2 mM KCN). A number of oxidative metabolites of [ 3H]DES were detected in the incubation medium of kidney slices incubated under aerobic, but not anaerobic, conditions. The amount of radiolabeled macromolecules formed in male cortical slices under aerobic conditions increased with time of incubation. At a medium concentration of 50 nM [ 3H]DES, 0.08 pmole [ 3H]DES equiv./mg dry weight at 30 min and 0.19 pmole [ 3H]DES equiv./mg dry weight at 120 min were observed. The amount of irreversible [ 3H]DES-macromolecular complexes also increased with the concentration of [ 3H]DES in the incubation medium: 1.59 pmole [ 3H]DES equiv./mg dry weight was formed with 0.5 μM[ 3H]DES and 21.89 pmole [ 3H]DES equiv./mg dry weight was formed with 10 μM [ 3H]DES. Non-extractable [ 3H]DES binding was detected in all the subcellular fractions of hamster kidney with the highest amount in the microsomal and soluble fractions, followed by the mitochondrial and nuclear fractions. The macromolecular-[ 3H]DES complexes were solubilized by proteases but not nucleases, suggesting that [ 3H]DES irreversible binding is principally to the proteins and not the nucleic acids. The cortex as compared with the medulla of the male hamster kidney displayed a 5-fold greater capacity to irreversibly bind [ 3H]DES metabolites. The male hamster renal cortex showed a 2- to 3-fold greater capacity to form irreversible macromolecular-[ 3H]DES complexes than the female hamster renal cortex. These data demonstrate that: (1) renal oxidative metabolism of DES results in [ 3H]DES metabolites binding irreversibly to macromolecules; and (2) the sex and organ site specificity of the [ 3H]DES-macromolecular binding corresponds with the sex and organ site specificity of renal tumors of the hamster.

In vitro metabolism of diethylstilbestrol by hepatic, renal and uterine microsomes of rats and hamsters : Effects of different inducers

In order to elucidate possible differences in the metabolism of the synthetic estrogen diethylstilbestrol (DES) by target and non-target tissues for DES carcinogenicity, the biotransformation of [ 14C]DES has been studied in vitro with hepatic and renal microsomes of male and female hamsters and rats, and from hamster and rat uterus. Of these tissues, only the male hamster kidney is susceptible to the carcinogenic effect of DES. Moreover, the effect of various inducers on the in vitro metabolism of DES has been investigated. It was found that male hamster kidney microsomes produced a markedly different pattern of DES metabolites as compared to renal microsomes from female hamster or male and female rats. Pretreatment with phenobarbital markedly increased oxidative DES metabolism by renal microsomes from female rat but not from male rat. Diethylstilbestrol metabolism by hepatic microsomes was different between hamster and rat, but was not sex-dependent and could not be significantly affected by pretreatment with phenobarbital, DES, 3-methylcholanthrene and 7:8-benzoflavone. The differences in DES metabolism between target and non-target organs and its modulation by inducers may help to gain further insight into the mechanism of DES tumorigenesis.

Covalent binding of diethylstilbestrol to microsomal protein in vitro correlates with the organotropism of its carcinogenicity.

[14C]Diethylstilbestrol (DES) was incubated in vitro with liver and kidney microsomes from male and female hamsters and rats, and the extent of non-extractable binding of radioactivity to microsomal protein was determined. Binding to microsomes from male hamster kidney, which is a target organ for DES carcinogenicity in vivo, was found to be 5-10 times higher than binding to microsomes from non-target tissues. Pretreatment with phenobarbital led to a marked increase in binding of DES to kidney microsomes but not to liver microsomes from female hamsters and male and female rats. The correlations of in vitro covalent binding with organ susceptibility implies a role for metabolic activation of DES in the mechanism of its carcinogenicity.

Interaction of estrone and estradiol with DNA and protein of liver and kidney in rat and hamster in vivo and in vitro.

[6,7-3H] Estrone (E) and [6,7-3H]estradiol-17 beta (E2) have been synthesized by reduction of 6-dehydroestrone and 6-dehydroestradiol with tritium gas. Tritiated E and E2 were administered by oral gavage to female rats and to male and female hamsters on a dose level of about 300 micrograms/kg (54 mCi/kg). After 8 h, the liver was excised from the rats; liver and kidneys were taken from the hamsters. DNA was purified either directly from an organ homogenate or via chromatin. The radioactivity in the DNA was expressed in the units of the Covalent Binding Index, CBI = (mumol chemical bound per mol DNA-P)/(mmol chemical administered per kg b.w.). Rat liver DNA isolated via chromatin exhibited the very low values of 0.08 and 0.09 for E and E2, respectively. The respective figures in hamster liver were 0.08 and 0.11 in females and 0.21 and 0.18 in the males. DNA isolated from the kidney revealed a detectable radioactivity only in the female, with values of 0.03 and 0.05 for E and E2, respectively. The values for male hamster kidney were less than 0.01 for both hormones. The minute radioactivity detectable in the DNA samples does not represent covalent binding to DNA, however, as indicated by two sets of control experiments. (A) Analysis by HPLC of the nucleosides prepared by enzyme digest of liver DNA isolated directly or via chromatin did not reveal any consistent peak which could have been attributed to a nucleoside-steroid adduct. (B) All DNA radioactivity could be due to protein contaminations, because the specific activity of chromatin protein was determined to be more than 3,000 times higher than of DNA. The high affinity of the hormone to protein was also demonstrated by in vitro incubations, where it could be shown that the specific activity of DNA and protein was essentially proportional to the concentration of radiolabelled hormone in the organ homogenate, regardless of whether the animal was treated or whether the hormone was added in vitro to the homogenate.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of steroid hormone treatment on aryl hydrocarbon hydroxylase activity in the Syrian hamster kidney

Aryl hydrocarbon hydroxylase (AHH) activity was determined in castrate and intact male Syrian hamster kidney and liver microsomes following in vivo treatment with either diethylstilbestrol (DES) or 17β-estradiol as well as other steroid hormones. After 1 month of estrogen treatment, there was a 5-fold decline in AHH activity in castrated hamster kidneys compared with untreated castrate levels. the amount of AHH activity in the kidney was depressed more than 75% of untreated castrate levels even after the estrogen had been withdrawn for 6 days. Consistent with a nearly 2.5-fold higher renal AHH activity observed in intact male hamsters compared to castrates was the finding of a 1.7-fold elevation in the activity of this enzyme after treatment of castrated animals with androgen[5α-dihydrotestrosterone (5α-DHT)] for 1 month. Moreover, following withdrawal of estrogen from intact hamsters, the increase in AHH activity in the kidney essentially paralleled the rise in serum testosterone levels. In castrated animals, the depression of AHH activity by estrogen was partially reversed by concomitant 5α-DHT treatment. However, no appreciable changes were seen in liver AHH activity with androgen treatment in the presence or absence of estrogen. Similarly, the level of AHH activity, which was nearly 7- and 14-fold higher than intact and castrate kidney levels, respectively, was not altered by estrogen treatment. Neither progesterone nor cortisone had any effect on the levels of AHH activity in either the kidney or liver. Therefore, AHH activity in the male hamster kidney, but not the liver, is responsive to both estrogens and androgenic hormone.

C 19-steroid 5β-reductase and 3- and 17-oxidoreductases of adult male hamster kidney

Male hamster kidney cytosol exhibited strong 5β-reductase activity. Incubation of cytosol with [4- 14C]-testosterone at pH 6.7 yielded 5β-DHT with minor quantities of 5β-androstane-3α,17β-diol and 5β-androstane-3β,17β-diol. Incubation with [4- 14C]-androstendione yielded 5β-androstanedione and smaller quantities of testosterone, 5β-DHT, 3α-hydroxy-5β-androstan-17-one, 3β-hydroxy-5β-androstan-17-one and 5β-androstane-3α,17β-diol. The two major metabolites were progressively increased with increase in the concentration of the respective substrates but the other metabolites showed very little change. The metabolism of the respective substrates was progressively decreased with changes in pH of the incubation mixture from 6.0–7.5 accompanied by a parallel decrease in the formation of the respective major metabolites. NADPH was much more effective than NADH as coenzyme. The microsomes exhibited a trace of 5β-reductase activity only with NADPH and androstenedione. The kidney homogenate at pH 10.1 effectively converted [4- 14C]-testosterone to [4- 14C]-androstenedione. The dehydrogenase activity was present in the cytosol and microsomes. NAD + was more effective than NADP + in the cytosol and the reverse was indicated for the microsomes. Spectrophotometric assay revealed not only NADP +-linked Hβ-dehydrogenase activity but also a lower 3α-dehydrogenase activity but no detectable 3β- or 17α-dehydrogenase activity. NAD +-linked activity was not explored because of the interference by the very high endogenous NAD +-reduetase activity.