Interactions between the environment and genes in the colon

Colorectal cancer is now widely accepted to be the result of an accumulation of mutations in specific genes controlling cell division, apoptosis and DNA repair. There is also a wealth of evidence that dietary factors, including dietary fat and fibre, influence the development of colorectal cancer. However, until recently, there has been little understanding of how these dietary factors and genetic factors interact. It is generally believed that this interaction is mediated in part by events occurring in the lumen of the large bowel. By characterizing the dietary/luminal factors that interact with the genes implicated in tumour development in the colon, a new understanding of colorectal cancer is likely to emerge, hopefully leading to the formulation of dietary recommendations to decrease the risk of this cancer.

Analysis of the major mercapturic acid pathway metabolites of benzo[a]pyrene found in rat urine by nano-electrospray mass spectrometry

Nano-electrospray has been used in combination with high resolution and tandem mass spectrometry in the analysis of the major mercapturic acid pathway metabolites of benzo[a]pyrene (BP). Accurate mass measurements indicate that the [M-H]- ion of the major metabolite has a chemical formula C25H22NO6S, which corresponds to the deprotonated form of tetrahydro-trihydroxy-BP-S-N-acetylcysteine. Tandem mass spectrometry of this [M-H]- ion results in a collision induced dissociation spectrum identical to that of synthetic 7,8,9,10-tetrahydro-8,9,10-trihydroxy-BP-7-S-N-acetylcysteine.

Expression of the peroxisome proliferator-activated receptor (PPAR) in the mouse colonic mucosa

The peroxisome proliferator-activated receptor (PPAR), a member of the steroid nuclear receptor superfamily, has been shown to be activated by various compounds such as fibrates, thiazolidinediones, prostaglandins, and fatty acids. Here we demonstrate expression of PPAR in mouse colonic and small intestinal mucosa by Western blot analysis and immunohistochemistry, indicating a higher expression level in the differentiated colonic epithelial cells facing the intestinal lumen. Quantification of PPAR mRNA by ribonuclease protection assay revealed relatively high expression of PPAR gamma and Nuc1 in the colon as compared to the small intestine. In contrast, PPAR alpha expression was higher in the small intestine as compared to the colon. These results demonstrate the presence of PPAR in the intestinal mucosa; however, the physiological roles of the various isoforms in the intestine remain to be established.

Increased c-fos mRNA and binding to the AP-1 recognition sequence accompanies the proliferative response to deoxycholate of HT29 cells

To further understand the molecular mechanisms of bile acid-mediated colon tumor promotion, we have examined the possible role of AP-1 activity in this process. The AP-1 complex has been reported to play an important role in control of cell growth. Our studies show that lithocholate, deoxycholate and ursodeoxycholate exhibited marked proliferative effects on a human adenocarcinoma cell line (HT29), while cholate was without effect. The proliferative effects appeared to be confined to narrow concentration windows which differed for the different bile acids. We demonstrate that deoxycholate caused an increase in expression of c-fos mRNA and increased binding to the AP-1 site, effects which were maximum at the concentration at which the bile acid induced the maximum proliferative effect on the cells. Cholate was without effect on AP-1 binding activity. In addition, we show that the AP-1 complex induced by treatment of the cells with the bile acid contained the c-fos protein. This could suggest that prolonged deregulated expression of AP-1 activity in colonic cells by certain bile acids may contribute to tumor promotion in the colon.

Influence of physical and chemical characteristics of diesel fuels and exhaust emissions on biological effects of particle extracts: a multivariate statistical analysis of ten diesel fuels

The emission of diesel exhaust particulates is associated with potentially severe biological effects, e.g., cancer. The aim of the present study was to apply multivariate statistical methods to identify factors that affect the biological potency of these exhausts. Ten diesel fuels were analyzed regarding physical and chemical characteristics. Particulate exhaust emissions were sampled after combustion of these fuels on two makes of heavy duty diesel engines. Particle extracts were chemically analyzed and tested for mutagenicity in the Ames test. Also, the potency of the extracts to competitively inhibit the binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to the Ah receptor was assessed. Relationships between fuel characteristics and biological effects of the extracts were studied, using partial least squares regression (PLS). The most influential chemical fuel parameters included the contents of sulfur, certain polycyclic aromatic compounds (PAC), and naphthenes. Density and flash point were positively correlated with genotoxic potency. Cetane number and upper distillation curve points were negatively correlated with both mutagenicity and Ah receptor affinity. Between 61% and 70% of the biological response data could be explained by the measured chemical and physical factors of the fuels. By PLS modeling of extract data versus the biological response data, 66% of the genotoxicity could be explained, by 41% of the chemical variation. The most important variables, associated with both mutagenicity and Ah receptor affinity, included 1-nitropyrene, particle bound nitrate, indeno[1,2,3-cd]pyrene, and emitted mass of particles. S9-requiring mutagenicity was highly correlated with certain PAC, whereas S9-independent mutagenicity was better correlated with nitrates and 1-nitropyrene. The emission of sulfates also showed a correlation both with the emission of particles and with the biological effects. The results indicate that fuels with biologically less hazardous potentials should have high cetane number and contain less PAC and sulfur. The results also indicate that engine factors affect the formation and emission of nitrated PAC.

Role of protein kinase C in growth stimulation of primary mouse colonic epithelial cells

The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (160 nM) and the secondary bile acid, deoxycholic acid (50 microM) stimulated DNA synthesis in quiescent primary epithelial cells from the normal mouse colon as measured by autoradiographic analysis of [3H]thymidine incorporation. The purpose of this present study was to investigate the involvement of protein kinase C in the proliferative response of the normal colonic cells. The protein kinase C inhibitor, bisindolyl-maleimide GF 109203X, efficiently blocked the proliferative response of the cells to the phorbol ester and caused a dose-dependent decrease in the response to deoxycholic acid. While the phorbol ester-induced proliferation was unaffected by another inhibitor, H-7, the response of the cells to deoxycholic acid was blocked. Pretreatment of the cells with the phorbol ester (160 nM) for 24 h blocked the proliferative response to deoxycholic acid. Measurement of the intracellular distribution of protein kinase C activity showed a time-dependent and significant translocation of the enzyme activity from the soluble to the particulate cell fractions after exposure to 12-O-tetradecanoylphorbol-13-acetate. While exposure to the bile acid indicated a similar time-dependent translocation of the enzyme activity, the effect was not significant. The phorbol ester induced a time-dependent accumulation of c-fos mRNA and protein was measured by solution hybridization and immunocytochemistry, respectively. No effect of deoxycholic acid on c-fos expression could be observed in the present study. The data support a role for protein kinase C in the growth stimulating effect of physiological concentrations of deoxycholic acid on normal colonic epithelial cells. However, differences in the mechanisms underlying phorbol ester- and bile acid-induced proliferation are indicated.

Binding of mutagenic heterocyclic amines by intestinal and lactic acid bacteria

Lactic acid bacteria have been reported to have antimutagenic/anticarcinogenic properties in vitro and in vivo. One possible mechanism for this effect involves a physical binding of the mutagenic compounds to the bacteria. The purpose of the present investigation was to study the binding capacity of eight human intestinal or lactic acid bacterial strains for mutagenic heterocyclic amines formed during cooking of protein-rich food. Binding of the mutagens Trp-P-2, PhIP, IQ and MeIQx by the bacterial strains was analyzed by HPLC. There were only minor differences in the binding capacities of the tested strains but the mutagenic compounds were bound with markedly different efficiencies. Trp-P-2 was almost completely bound and the binding tended not to be of a reversible nature. The binding of PhIP, which reached about 50%, was important as PhIP is a major mutagen in the western diet. IQ and MeIQx were slightly less well bound. pH appeared to be of importance for the binding efficacy. Binding correlated well with the reduction in mutagenicity observed after exposure of the heterocyclic amines to the bacterial strains. The results indicate that cooked food mutagenic compounds, commonly found in the western meat-rich diet, can be bound to bacteria from the normal intestinal microflora in vitro.

Characterization of neutral metabolites of benzo[a]pyrene in urine from germfree rats

[14C]Benzo[a]pyrene (BP) was administered to male germfree rats. Urinary metabolites, constituting 9% of the administered radioactivity, were fractionated by lipophilic ion exchange chromatography. More than 80% of the urinary metabolites were conjugated, while neutral metabolites constituted 13-18%. The latter group was characterized by reversed-phase HPLC, ultraviolet spectrometry (UV) and gas chromatography/mass spectrometry (GC/MS). Relative quantities of BP metabolites were estimated from the distribution of radioactivity upon HPLC fractionation. Some coeluted peaks were further quantitated from the total ion current chromatograms obtained in the GC/MS analysis. Two 7,8,9,10-tetrols which might be produced from the ultimate carcinogen r-7-t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydro-BP (anti-7,8-diol-9,10-epoxide) were detected at trace levels and indicated to be the r-7-t-8,9-c-10-(7,10/8,9-) and r-7-t-8,9,10-(7/8,9,10-) isomers. A trans-11,12-dihydrodiol was characterized as a major metabolite, while a trans-7,8-dihydrodiol was present at trace levels. Three additional quantitatively important metabolites were identified as isomeric trihydroxy-BPs. Two metabolites coeluting with BP quinones on HPLC were detected with relatively high abundance and tentatively identified as carboxylic methyl ester derivatives of BP quinones. Three quinones were detected with 1,6-, 3,6- and 6,12-substitutions. The 6,12- and 11,12-dihydroxy-BPs were also found at trace levels. A group of quinone-like metabolites were tentatively identified as trioxo-BPs. No monohydroxy-BP was detected in the neutral fraction of the urine extract. The time course of excretion was also studied and found to differ between individual metabolites.

Increases in 13-hydroxyoctadecadienoic acid dehydrogenase activity during differentiation of cultured cells

Recently, oxidation products of linoleic acid such as 13-hydroxyoctadecadienoic acid (HODE) have been implicated in the regulation of cellular physiology including the proliferative response to growth factor treatment. In addition, an NAD(+)-dependent 13-HODE dehydrogenase was recently described. To evaluate the contribution of this enzyme to cellular processes we have examined the behavior of the enzyme under different conditions. In the present report, changes in the activity of 13-hydroxyoctadecadienoic acid dehydrogenase during in vitro differentiation of two different cell lines were examined. The cell line HT-29 undergoes induced differentiation via manipulation of the medium while the Caco-2 line undergoes spontaneous differentiation upon attainment of confluence. In both cell lines, longer culture times were accompanied by increases in 13-HODE dehydrogenase activity. The increase in enzyme activity continued even after cell proliferation had ceased. Cellular differentiation was verified by the observation of increases in sucrase and alkaline phosphatase activities. In addition, the activity of 13-HODE dehydrogenase was measured in growing, early confluent and late confluent cultures of undifferentiating Swiss mouse 3T3 fibroblasts. In the fibroblast line, no significant changes in 13-HODE dehydrogenase activity were observed during the course of the experiment. The specific activity of 13-HODE dehydrogenase was also significantly different between the three cell lines, consistent with the extent of differentiation. Highest levels of activity were found in Caco-2 cells (200-400 pmol/min/mg) and barely detectable levels in the fibroblasts (0.6-2 pmol/min/mg). The correlation between 13-HODE dehydrogenase and cell differentiation suggests the enzyme may have a role to play in the partitioning of cells between proliferation and differentiation pathways.

Lactobacilli, anticarcinogenic activities and human intestinal microflora

Lactobacilli belong to the normal oropharyngeal and intestinal microflora in humans. These microorganisms contribute to the stabilization of the microflora and maintain the colonization resistance against pathogens. Lactobacilli have been used as dietary supplements in order to prevent gastrointestinal disturbances. Claims have been made that certain strains of lactobacilli possibly exert anticarcinogenic activities. The activity of bacterial enzymes, implicated in colon carcinogenesis may be elevated by a high meat, Western-type diet. Supplements of Lactobacillus acidophilus decreased these levels in both rats and humans. Colon cancer patients given L. acidophilus fermented milk showed a significant increase both in numbers of intestinal lactobacilli and dietary calcium intake, while decreasing trends in levels of both soluble faecal bile acids and faecal bacterial enzymes, two risk makers for colon cancer, were observed. In vitro studies have revealed that lactobacilli and other lactic acid bacteria have the ability to absorb cooked food mutagens. Recent studies in humans have shown that intake of L. acidophilus significantly reduced the mutagen excretion after consumption of fried meat. Several mechanisms by which lactobacilli might exert anticarcinogenic effects are discussed. Thus, certain strains of lactobacilli might lower the colon cancer risk in humans.

Proliferative potential and expression of cell type specific functions in primary mouse colonic epithelial cells

Primary cultures of mouse colonic epithelial cells have been obtained that are typically epithelial by morphology and moreover express keratins and endogenous beta-galactosidase; this latter activity was also demonstrated in the epithelial lining of the mouse colonic mucosa. The proliferative response of the primary colonic epithelial cells to epidermal growth factor, insulin, and the bile acid, deoxycholic acid, has been studied. Using primary cultures maintained at suboptimal growth conditions, which yielded 96 to 100% quiescent cells, epidermal growth factor, insulin, and the bile acid, deoxycholic acid, at concentrations at which it normally occurs in the aqueous phase of human feces, stimulated proliferation as measured by autoradiography. Exposure of the cells to combinations of these factors resulted in additive increases in growth. In conclusion, cells from the normal mouse colon can now be cultured while retaining at least two normal marker functions and moreover respond to some known mitogens and the potential tumor promoter deoxycholic acid. The cells can also be subcultivated while maintaining their epithelial morphology and marker functions for at least 3 passages.

Progesterone metabolism in the microsomal fraction of the testis, head kidney, and trunk kidney from the rainbow trout

In the present study on male rainbow trout, well-defined microsomal fractions from gonad, trunk kidney, and head kidney were used to study enzymes active on progesterone. The metabolites produced were identified by mass spectrometric analysis. In the testis the main metabolite was 17 alpha-hydroxyprogesterone which is an intermediate in the steroid biosynthetic pathway. 17 alpha-Hydroxyprogesterone was also identified in incubations from head and trunk kidney. The 17 alpha-hydroxylase activity was higher in the head kidney than in the trunk kidney which probably reflects the presence of steroid producing interrenal cells in this part of the kidney. The conversion of progesterone to 17 alpha-hydroxylated products in the testis and head kidney was NADPH dependent and inhibited by carbon monoxide, indicating the participation of cytochrome P450 monooxygenase in this reaction. NADH supported the reaction to some extent (27% of the NADPH-dependent activity) in the testis but not in the head kidney. In addition to 17 alpha-hydroxyprogesterone the head and trunk kidney microsomes gave rise to 16 alpha- and 6 beta-hydroxyprogesterone. These activities were low or absent in testis microsomes. Progesterone 5 alpha-reductase activity was only detected in trunk kidney microsomes.

Tissue localization of the carcinogenic glutamic acid pyrolysis product Glu-P-1 in control and beta-naphthoflavone-treated mice and rats

Autoradiograms obtained after i.v. injection of the 14C-labelled carcinogenic glutamic acid pyrolysis product Glu-P-1 to mice and rats showed a pronounced uptake of radioactivity in the liver, kidney, thyroid and nasal mucosa. High concentrations of radioactivity were present in the bile and intestinal contents at short post-injection times. In the male rat, the Zymbal's gland and the preputial gland were identified as sites of high and specific binding at all post-injection times examined. The liver and nasal mucosa were identified as sites of retention of non-extractable radioactivity. In the pigmented mouse, Glu-P-1 and/or its metabolites were accumulated in melanin. Glu-P-1 is known to be activated by cytochrome P-448. Pretreatment with beta-naphthoflavone (a cytochrome P-448 inducer) did not change the tissue localization of radioactivity in either species except for the liver where the overall labelling was decreased. Neither did pretreatment of mice with the glutathione-depleting agent phorone change the distribution pattern significantly. However, combined pretreatments of mice with either phorone or beta-naphthoflavone and the cytochrome P-448 inhibitor 9-hydroxyellipticine resulted in an increased overall retention of radioactivity in the body.

Association between asthenia and nutritional status, lean body mass, anemia, psychological status, and tumor mass in patients with advanced breast cancer

Sixty-four consecutive patients with advanced breast cancer were included in a study designed to determine the prevalence of asthenia and its association with other clinical features. The Asthenia Score (AS, the average of four tests designed by our group to assess asthenia) was 59 +/- 9 for patients versus 88 +/- 7 for a group of 68 normal controls (p less than 0.001). Twenty-six patients (41%) scored below the tenth percentile of normal controls and were considered asthenics. AS was correlated with depression and the general severity index of the SCL-90 R test. No association was found between AS and nutritional status, lean body mass, tumor mass, anemia, or type of treatment. We conclude that asthenia is a frequent symptom in patients with advanced breast cancer, which, in our series, showed independent correlations only with psychological distress.

Fecal diglycerides as selective endogenous mitogens for premalignant and malignant human colonic epithelial cells

Diglycerides (DGs) have been found in fecal extracts at concentrations which induce mitogenesis of adenoma and some carcinoma cells but not normal cells in primary culture. DGs containing stearic, oleic, palmitic, and myristic acid side chains were found in fecal extracts from each of eight subjects. Synthetic 1,2-DGs, containing the fatty acids found in endogenous fecal DGs, induced mitogenesis in cultures of premalignant cells from each of 13 adenomas, covering all histological classes, and in cultures from two of four carcinomas. The potent adenoma mitogen, dimyristin, had no mitogenic activity on cultures of normal colonic epithelial cells from seven different subjects. These results suggest DGs may act as endogenous mitogens in the development of human colon cancer. The extent of adenoma mitogenesis was correlated with the chain length of the saturated R-groups: 16 greater than 14 greater than 12 greater than 10 greater than 8 much greater than 18. DGs with oleic acid residues, C18:1, were among the most active, while substitution of even one fatty acid residue with a stearic acid residue, C18:0, reduced or eliminated mitogenic activity. Dimyristin also induced enhanced levels of urokinase secretion from carcinoma cells, in parallel to the phorbol ester tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. These results imply that DGs found in the colon induce a selective growth of benign colonic tumors and some carcinomas, and may enhance the invasive capacity of carcinomas, while leaving normal cells unaffected.

Effects of triethyl lead chloride on oestradiol metabolism in the female rat liver microsomal fraction

Triethyl lead chloride (TEL) was added directly to female rat liver microsomal fractions at final concentrations of 0.0, 0.005, 0.05 and 0.5 mM, respectively. The effect of oestradiol on liver microsomal metabolism was studied in vitro by incubating the microsomes with radioactive oestradiol-17 beta. The oestradiol metabolites were separated, identified and quantified. The highest treatment concentrations resulted in decreased activities of enzymes that metabolize oestradiol-17 beta.

The role of the intestinal microflora in the formation of mutagenic metabolites from the carcinogenic air pollutant 2-nitrofluorene

After a single oral dose of 2-nitro[9-14C]fluorene (NF) to germfree and conventional rats, radioactivity with associated mutagenic activity was rapidly excreted in both urine and feces. The mutagenicity excreted from germfree animals exceeded the mutagenicity excreted from conventional animals. Absence of the microflora resulted in lack of nitroreduction and excreted metabolites from germfree rats were mono- or dihydroxylated nitrofluorenes, as assessed by liquid chromatography/mass spectrometry (LC/MS). These hydroxy-NFs were associated with the high direct-acting mutagenicity that was excreted in germfree animals. Only traces of NF were found in urine from germfree rats and no NF was detected in urine from conventional animals. Thus, in contrast to a number of reports on other mutagenic compounds, these results would tend to indicate that the intestinal microflora causes a reduced excretion of mutagenic metabolites of NF.

Metabolism of the carcinogenic air pollutant 2-nitrofluorene in the isolated perfused rat lung and liver

The metabolism of 2-nitrofluorene (NF), a model substance for nitrated polycyclic aromatic hydrocarbons, was studied in the isolated perfused rat lung and liver. NF has been identified in urban air and diesel exhaust and occurs in the gas, as well as in the particulate phase. Therefore, it is conceivable that the lung represents one point of entry of this compound into the body. The lung metabolizes NF to hydroxylated NFs, mainly 9-hydroxy-NF, independently of the route of administration (intravascular or intratracheal). After intratracheal administration, NF is rapidly excreted into the perfusate, indicating that other organs might be exposed to unmetabolized NF. The liver excretes NF metabolites as biliary glucuronides. Untreated bile is not mutagenic. However, after beta-glucuronidase treatment of bile, direct-acting mutagens were detected. The mutagenic metabolites in beta-glucuronidase-treated bile were the same as identified in the perfusate of the isolated lung. Since beta-glucuronidase is an enzyme found in the human intestinal microflora, inhalation of NF could result in the liberation of genotoxic metabolites in the colon.

Metabolism of the carcinogenic air pollutant 2-nitrofluorene in the rat

After a single oral dose of 2-nitro [9-14C]fluorene to rats, radioactivity with associated mutagenic activity was rapidly excreted in both urine and faeces, urine being the major excretory route. The major part of the urinary mutagenicity was associated with the unconjugated fraction of metabolites which consisted of a range of hydroxylated acetylaminofluorenes in addition to a number of hydroxylated nitrofluorenes. The formation of hydroxylated acetylaminofluorenes supports the contention that 2-nitrofluorene, in vivo, enters the metabolic pathway of the well-known carcinogen 2-acetylaminofluorene. The single most mutagenic metabolite of 2-nitrofluorene was a hydroxylated nitrofluorene; the formation of this metabolite was markedly increased when the rats had been treated with beta-naphthoflavone. Finally, an alternative pathway is discussed for the formation of 1- and 3-hydroxyacetylaminofluorenes.

Studies on the chromatographic fractionation of metabolites of benzo[a]pyrene in faeces and urine from germfree and conventional rats

Rats, germfree and conventional, were dosed with 14C-labelled benzo[a]pyrene. Faeces and urine were collected. Metabolites in faeces were effectively extracted with a new method using a combination of solvents and solid sorbents. Metabolites in urine were extracted with octadecylsilane-bonded silica. The metabolites were fractionated into groups by chromatography on a cation exchanger (SP-LH-20 or SP-Sephadex C-25) and an anion exchanger (TEAP-LH-20). Some of the groups were further purified by column chromatography and analysed by HPLC and TLC. The analyses show a complex pattern of metabolism. A large part of the metabolites (9-24% depending on animal type and route of excretion) had amphoteric properties, e.g. like glutathione and cysteine conjugates. The abundance of conjugates sensitive to beta-glucuronidase and sulphatase was low. The relative amount of acidic conjugates in faeces was much higher in the germfree than in the conventional rats indicating the influence of the intestinal flora on the metabolism. The results support the view that the mercapturic acid pathway is a quantitatively important metabolic route for benzo[a]pyrene in rats. The methods of extraction and group fractionation were designed to be generally applicable to the analysis of lipophilic xenobiotics and their metabolites.

Calcium enhances the hemolytic action of bile salts

The lysis of human erythrocytes by bile salts in buffer containing isotonic saline was dramatically enhanced by the addition of 5-10 mM calcium chloride. All bile acids tested showed this effect, with a marked increase in lysis occurring at 0.75 mM for deoxycholate, 1 mM for chenodeoxycholate, 2.5 mM for ursodeoxycholate and 5.5 mM with cholate in the presence of 10 mM calcium chloride. The effect appeared to be specific for calcium; strontium chloride and magnesium chloride gave no stimulatory effect. The increased lysis of the erythrocytes in the presence of 1 mM deoxycholate and 1-10 mM calcium chloride was not associated with increased uptake of the bile salt by the cells (measured with [14C]deoxycholate). Using erythrocytes previously labelled with [3H]cholesterol, there was no evidence of an enhanced removal of that membrane component in the presence of calcium and deoxycholate, compared to deoxycholate alone. The sensitivity of the cells to the effect of calcium in the presence of 1 mM deoxycholate increased with the length of time of their storage at 4 degrees C. The sensitivity returned to that of fresh cells after incubation at 37 degrees C with 30 mM adenosine plus 25 mM glucose, but this treatment did not further diminish the lysis. Lysis in the presence of 10 mM calcium chloride and 1 mM deoxycholate was partially blocked by increasing the KCl concentration at the expense of NaCl. The maximum effect occurred with a buffer comprising 100 mM KCl/50 mM NaCl. A more dramatic reduction in the lysis followed the incorporation of the calcium chelator, quin2, into the cells. The lysis induced by 1 mM deoxycholate in the presence of calcium was reduced by 80% in quin-2-loaded cells compared to controls. The data suggest that bile acids can promote the influx of calcium into erythrocytes, leading to lysis as a result of the efflux of intracellular potassium and/or the uptake of sodium from the incubation medium. The data further suggest that cellular effects may occur at lower bile acid concentrations than that thought to be required for detergent damage.

Insurance premium reductions. A motivating factor in long-term hypertensive treatment

Elevated blood pressure substantially increases mortality and requires, therefore, high premium payments for life insurance coverage. Most life insurance companies are willing to reduce the cost of yearly premiums when blood pressure is successfully treated and controlled for several years. Physicians should bring these facts to their patients' attention as a motivating factor to improve adherence to therapy.

Distribution of the carcinogenic tryptophan pyrolysis product Trp-P-1 in control, 9-hydroxyellipticine and beta-naphthoflavone pretreated mice

Autoradiograms obtained 1-4 h after i.v. injection of the 14C-labelled carcinogenic tryptophan pyrolysis product Trp-P-1 to albino and pigmented mice showed a pronounced uptake of radioactivity in the lymphatic system (thymus, lymph nodes, bone marrow and spleen), in the endocrine system (hypophysis, thyroid, adrenal medulla) and in the liver, kidney medulla and brain. High radioactivity was present in the excretory pathways, predominantly in the bile/intestinal contents. At longer post-injection times (24 h to 6 days) most of the labelled substance had left the tissues, except for the liver which still retained a high concentration of radioactivity. Trp-P-1 is known to be activated by cytochrome P-448. The uptake of radioactivity in the liver could be reduced by pretreatment with the cytochrome P-448 inhibitor 9-hydroxyellipticine suggesting that the observed accumulation of radioactivity in the liver was partly due to metabolites of Trp-P-1. After pretreatment with the cytochrome P-448 inducer beta-naphthoflavone, the administration of Trp-P-1 resulted in a highly selective accumulation of radioactivity in the lung parenchyma, exceeding all other tissues in the body. beta-Naphthoflavone pretreatment also increased the uptake of radioactivity in the kidney cortex and small intestinal mucosa. As indicated by a high labelling of the pigmented tissues of the maternal and fetal eye, the carcinogen and/or its metabolites were accumulated in melanin.

In vitro metabolism of estradiol-17 beta by liver microsomes from juvenile rainbow trout, Salmo gairdneri

The metabolism of [4-14C]estradiol-17 beta by liver microsomes from, Salmo gairdneri, was studied in vitro. The following metabolites were identified by gas chromatography--mass spectrometry: estrone, estra-1,3,5(10)-triene-3,16 beta,17 beta-triol, and estra-1,3,5(10)-triene-3,7 alpha,17 beta-triol. The presence of additional polar metabolites hydroxylated at positions 6 alpha and 6 beta was indicated. The formation of the hydroxylated metabolites was inhibited by CO indicating the participation of cytochrome P-450-dependent enzymes.

Metabolism of 2,4',5-trichlorobiphenyl: tissue concentrations of methylsulphonyl-2,4',5-trichlorobiphenyl in germfree and conventional mice

Whole-body autoradiography of 2,4',5-[14C]trichlorobiphenyl ([14C]triCB) indicated that, whereas there was accumulation of radioactivity in the tracheobronchial mucosa of conventional (C) mice 1-7 days after injection, no such effect was observed in germfree (GF) mice 1 day after injection. At days 4 and 7 there was a low, but significant, uptake by the tracheobronchial mucosa of the GF mice. Chemical analysis showed that the concentrations of 4-methylsulphonyl-triCB (4-MeSO2-triCB) in lung, kidney and liver 7 days after administration of triCB were 6.5, 14.7 and 3.7 times higher, respectively, in C than in GF mice. The results are interpreted as indicating the existence of a major metabolic route to triCB methyl sulphones involving the intestinal microflora, and a minor route, not requiring the flora.

Metabolism of 2,4',5-trichlorobiphenyl: role of the intestinal microflora in the formation of bronchial-seeking methyl sulphone metabolites in mice

Groups of germ-free and conventional mice were treated with 2,4',5-trichlorobiphenyl (triCB) and [35S]cysteine or [35S]methionine, respectively. Control animals received the labelled amino acids only. Conventional mice accumulated significantly more extractable radioactivity both in lung and kidney tissues when compared to germ-free mice. The extracted radioactivity in lung and kidney tissues was shown to be due to the accumulation of methyl-[35S]sulphonyl-triCB. The low radioactivity in lungs of the germ-free mice was also shown to be due to the accumulation of small amounts of the sulphones. The results indicate an involvement of the intestinal flora in the formation of methyl sulphone metabolites of triCB.

Enterohepatic circulation of the mercapturic acid and cysteine conjugates of propachlor

Germfree (GF) rats and antibiotic-treated rats with cannulated bile ducts (ABC) were given single oral doses of 2-(S-(N-[2H3]acetyl)cysteine)-N-isopropyl[1-14C]acetanilide. The GF rats excreted the dose in about equal quantities in the urine and feces; and the ABC rats excreted the dose in about equal quantities in the urine, feces, and bile. The mercapturate (60-75% of the dose in both cases) was isolated and the amount of exchange of N-acetyl deuterium to N-acetyl hydrogen was determined for all samples by mass spectrometry. The percentages of exchange were: ABC rats, bile 6.5%, urine 13%, feces 0.0%; GF rats, urine 15%, feces 4.7%. The remainder of the doses was present as the mercapturic acid sulfoxide. ABC rats dosed with 2-(S-[3,3-3H]cysteine)-N-isopropyl[1-14C]acetanilide (14C/3H = 0.50) excreted 42% of the dose in the urine and bile as the mercapturic acid that had a 14C/3H ratio the same as the original cysteine conjugate. The results of these studies show that a mercapturic acid and a cysteine conjugate can be absorbed from the gastrointestinal tract and resecreted in the bile or excreted by the kidney without having undergone metabolism other than acetylation of the cysteine nitrogen atom and oxidation of the sulfur to a sulfoxide. ABC rats were also dosed with 2-methylthio-N-isopropyl[1-14C]acetanilide, a suspected metabolic intermediate in the metabolism of propachlor (2-chloro-N-isopropylacetanilide). The dose was excreted in about equal quantities in the bile (48%) and urine (46%) as metabolites with a methylsulfonyl group in the 2-position. All are known metabolites of propachlor in conventional rats.

Effects of treatment with chenodeoxycholic acid on liver microsomal metabolism of steroids in man

The present investigation was undertaken to evaluate whether treatment of gallstone patients with chenodeoxycholic acid is associated with changes of the hepatic metabolism of steroids. Altogether 37 patients with cholesterol gallstones undergoing cholecystectomy were included in the study. Nine of them had been treated with chenodeoxycholic acid (15 mg/kg/day) for about 8 weeks prior to operation. Two hydroxylations involved in cholic acid biosynthesis, 12 alpha-hydroxylation of 7 alpha-hydroxycholest-4-en-3-one and 25-hydroxylation of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol, and the metabolism of a physiological steroid hormone, androst-4-ene-3, 17-dione, were studied in the microsomal fraction of liver homogenates. The 12 alpha-hydroxylase was inhibited about 50%, which is in accordance with a regulatory function of this enzyme. The 25-hydroxylase and the metabolism of androst-4-ene,3, 17-dione were unaffected. It is concluded that chenodeoxycholic acid treatment is not associated with general influences on hepatic steroid metabolism.