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To a Question on the Mechanism of the Antimicrobial Action of Ortho-Benzoic Sulfimide. Pharmaceuticals (Basel) 2020; 13:ph13120461. [PMID: 33322230 PMCID: PMC7763927 DOI: 10.3390/ph13120461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 11/16/2022] Open
Abstract
The article summarizes and compares data on the properties and biological activity of o-benzoic sulfimide and sulfanilamide compounds. Attention is given to the biochemical conditions under which o-benzoic sulfimide and sulfanilamides have similar activity groups. The results of the experimental and theoretical studies aimed at understanding the molecular organization and biological activity of folic acid and its homologous complexes are analyzed. A hypothesis about the possible mechanisms of the formation of such complexes with the participation of o-benzoic sulfimide is presented. The perspectives for the use of o-benzoic sulfimide and its homologues in biomedicine are evaluated.
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Kapil V, Khambata RS, Jones DA, Rathod K, Primus C, Massimo G, Fukuto JM, Ahluwalia A. The Noncanonical Pathway for In Vivo Nitric Oxide Generation: The Nitrate-Nitrite-Nitric Oxide Pathway. Pharmacol Rev 2020; 72:692-766. [DOI: 10.1124/pr.120.019240] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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3
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Broesder A, Kosta AMMAC, Woerdenbag HJ, Nguyen DN, Frijlink HW, Hinrichs WLJ. pH-dependent ileocolonic drug delivery, part II: preclinical evaluation of novel drugs and novel excipients. Drug Discov Today 2020; 25:1374-1388. [PMID: 32562842 DOI: 10.1016/j.drudis.2020.06.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 05/18/2020] [Accepted: 06/08/2020] [Indexed: 01/18/2023]
Abstract
Novel drugs and novel excipients in pH-dependent ileocolonic drug delivery systems have to be tested in animals. Which animal species are suitable and what in vivo methods are used to verify ileocolonic drug delivery?
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Affiliation(s)
- Annemarie Broesder
- University of Groningen, Groningen Research Institute of Pharmacy, Department of Pharmaceutical Technology and Biopharmacy, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Anne-Marijke M A C Kosta
- University of Groningen, University Medical Center Groningen, Department of Biomedical Sciences of Cells and Systems, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Herman J Woerdenbag
- University of Groningen, Groningen Research Institute of Pharmacy, Department of Pharmaceutical Technology and Biopharmacy, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Duong N Nguyen
- University of Groningen, Groningen Research Institute of Pharmacy, Department of Pharmaceutical Technology and Biopharmacy, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Henderik W Frijlink
- University of Groningen, Groningen Research Institute of Pharmacy, Department of Pharmaceutical Technology and Biopharmacy, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Wouter L J Hinrichs
- University of Groningen, Groningen Research Institute of Pharmacy, Department of Pharmaceutical Technology and Biopharmacy, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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Mortensen A, Aguilar F, Crebelli R, Di Domenico A, Dusemund B, Frutos MJ, Galtier P, Gott D, Gundert-Remy U, Lambré C, Leblanc JC, Lindtner O, Moldeus P, Mosesso P, Oskarsson A, Parent-Massin D, Stankovic I, Waalkens-Berendsen I, Woutersen RA, Wright M, van den Brandt P, Fortes C, Merino L, Toldrà F, Arcella D, Christodoulidou A, Barrucci F, Garcia A, Pizzo F, Battacchi D, Younes M. Re-evaluation of sodium nitrate (E 251) and potassium nitrate (E 252) as food additives. EFSA J 2017; 15:e04787. [PMID: 32625505 PMCID: PMC7010087 DOI: 10.2903/j.efsa.2017.4787] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The Panel on Food Additives and Nutrient Sources added to Food (ANS) provided a scientific opinion re-evaluating the safety of sodium nitrate (E 251) and potassium nitrate (E 252) when used as food additives. The current acceptable daily intakes (ADIs) for nitrate of 3.7 mg/kg body weight (bw) per day were established by the SCF (1997) and JECFA (2002). The available data did not indicate genotoxic potential for sodium and potassium nitrate. The carcinogenicity studies in mice and rats were negative. The Panel considered the derivation of an ADI for nitrate based on the formation of methaemoglobin, following the conversion of nitrate, excreted in the saliva, to nitrite. However, there were large variations in the data on the nitrate-to-nitrite conversion in the saliva in humans. Therefore, the Panel considered that it was not possible to derive a single value of the ADI from the available data. The Panel noticed that even using the highest nitrate-to-nitrite conversion factor the methaemoglobin levels produced due to nitrite obtained from this conversion would not be clinically significant and would result to a theoretically estimated endogenous N-nitroso compounds (ENOC) production at levels which would be of low concern. Hence, and despite the uncertainty associated with the ADI established by the SCF, the Panel concluded that currently there was insufficient evidence to withdraw this ADI. The exposure to nitrate solely from its use as a food additive was estimated to be less than 5% of the overall exposure to nitrate in food based on a refined estimated exposure scenario. This exposure did not exceed the current ADI (SCF, 1997). However, if all sources of exposure to dietary nitrate are considered (food additive, natural presence and contamination), the ADI would be exceeded for all age groups at the mean and the highest exposure.
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Min TS, Park MJ, Moon JH, Kim WS, Lee SH, Cho YD, Park SH. Bio-active Substances and Physiological Activity of Pears. ACTA ACUST UNITED AC 2013. [DOI: 10.3839/jabc.2013.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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A mammalian functional nitrate reductase that regulates nitrite and nitric oxide homeostasis. Nat Chem Biol 2008; 4:411-7. [PMID: 18516050 DOI: 10.1038/nchembio.92] [Citation(s) in RCA: 248] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Accepted: 05/08/2008] [Indexed: 11/09/2022]
Abstract
Inorganic nitrite (NO(2)(-)) is emerging as a regulator of physiological functions and tissue responses to ischemia, whereas the more stable nitrate anion (NO(3)(-)) is generally considered to be biologically inert. Bacteria express nitrate reductases that produce nitrite, but mammals lack these specific enzymes. Here we report on nitrate reductase activity in rodent and human tissues that results in formation of nitrite and nitric oxide (NO) and is attenuated by the xanthine oxidoreductase inhibitor allopurinol. Nitrate administration to normoxic rats resulted in elevated levels of circulating nitrite that were again attenuated by allopurinol. Similar effects of nitrate were seen in endothelial NO synthase-deficient and germ-free mice, thereby excluding vascular NO synthase activation and bacteria as the source of nitrite. Nitrate pretreatment attenuated the increase in systemic blood pressure caused by NO synthase inhibition and enhanced blood flow during post-ischemic reperfusion. Our findings suggest a role for mammalian nitrate reduction in regulation of nitrite and NO homeostasis.
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7
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Coates ME, Walker R. Interrelationships between the Gastrointestinal Microflora and Non-Nutrient Components of the Diet. Nutr Res Rev 2007; 5:85-96. [DOI: 10.1079/nrr19920008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Sobko T, Reinders C, Norin E, Midtvedt T, Gustafsson LE, Lundberg JO. Gastrointestinal nitric oxide generation in germ-free and conventional rats. Am J Physiol Gastrointest Liver Physiol 2004; 287:G993-7. [PMID: 15256364 DOI: 10.1152/ajpgi.00203.2004] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Nitric oxide (NO) is a central mediator of various physiological events in the gastrointestinal tract. The influence of the intestinal microflora for NO production in the gut is unknown. Bacteria could contribute to this production either by stimulating the mucosa to produce NO, or they could generate NO themselves. Using germ-free and conventional rats, we measured gaseous NO directly in the gastrointestinal tract and from the luminal contents using a chemiluminescence technique. Mucosal NO production was studied by using an NO synthase (NOS) inhibitor, and to evaluate microbial contribution to the NO generation, nitrate was given to the animals. In conventional rats, luminal NO differed profoundly along the gastrointestinal tract with the greatest concentrations in the stomach [>4,000 parts per billion (ppb)] and cecum (approximately 200 ppb) and lower concentrations in the small intestine and colon (< or =20 ppb). Cecal NO correlated with the levels in incubated luminal contents. NOS inhibition lowered NO levels in the colon, without affecting NO in the stomach and in the cecum. Gastric NO increased greatly after a nitrate load, proving it to be a substrate for NO generation. In germ-free rats, NO was low (< or =30 ppb) throughout the gastrointestinal tract and absent in the incubated luminal contents. NO also remained low after a nitrate load. Our results demonstrate a pivotal role of the intestinal microflora in gastrointestinal NO generation. Distinctly compartmentalized qualitative and quantitative NO levels in conventional and germ-free rats reflect complex host microbial cross talks, possibly making NO a regulator of the intestinal eco system.
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Affiliation(s)
- Tanja Sobko
- Centre for Allergy Research, Karolinska Institutet, S-17177 Stockholm, Sweden.
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Larauche M, Anton PM, Garcia-Villar R, Theodorou V, Frexinos J, Buéno L, Fioramonti J. Protective effect of dietary nitrate on experimental gastritis in rats. Br J Nutr 2003; 89:777-86. [PMID: 12828794 DOI: 10.1079/bjn2003845] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Nitrates have long been considered as harmful dietary components and judged responsible for deleterious effects on human health, leading to stringent regulations concerning their levels in food and water. However, recent studies demonstrate that dietary nitrate may have a major role in human health as a non-immune mechanism for host defence, through its metabolism to NO in the stomach. NO is a versatile molecule and although evidence exists showing that administration of low doses of exogenous NO protects against gastrointestinal inflammation, higher NO doses have been shown to exacerbate injury. So, the effect of an ingestion of nitrates in doses corresponding to a normal diet in human consumers on an experimental gastritis induced by iodoacetamide in rats was investigated. During gastritis one of the following compounds was given orally: water; KNO3; the NO donor sodium nitroprusside; the NO scavenger haemoglobin given with either water or KNO3. N(G)-nitro-l-arginine methyl ester (l-NAME), a non-specific NO synthase inhibitor, was administered with either water, iodoacetamide alone, or combined with KNO3. After killing, the stomach was resected and microscopic damage scores, myeloperoxidase and NO synthase activities were determined. Iodoacetamide-induced gastritis was significantly reduced by KNO3 administration, an effect which was reproduced by sodium nitroprusside and reversed by haemoglobin. l-NAME induced gastric mucosal damage in itself, and KNO3 did not prevent the gastritis induced by iodoacetamide associated with l-NAME. In conclusion, dietary nitrate exerts a protective effect against an experimental gastritis in rats by releasing NO in the stomach but such an effect requires the production of endogenous NO.
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Affiliation(s)
- Muriel Larauche
- Neuro-Gastroenterology and Nutrition Unit, Institut National de la Recherche Agronomique, 180 chemin de Tournefeuille, BP3, 31931 cedex 9, France
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Rouzade ML, Anton P, Fioramonti J, Garcia-Villar R, Theodorou V, Bueno L. Reduction of the nociceptive response to gastric distension by nitrate ingestion in rats. Aliment Pharmacol Ther 1999; 13:1235-41. [PMID: 10468707 DOI: 10.1046/j.1365-2036.1999.00611.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
BACKGROUND Dietary nitrates are known to produce nitric oxide in the stomach, which may influence gastric function. AIM To investigate whether nitrate ingestion modifies gastric sensitivity to distension through a mechanism involving nitric oxide production. METHODS Nociception, associated with gastric distension ranging from 10 to 40 mmHg, was assessed in anaesthetized rats by the amplitude of cardiovascular depressor responses. Gastric volume corresponding to each distension was recorded. The following intragastric administrations (1 mL) were performed before distension: water (control), KNO3, NaNO3, KCl, NaCl (all at 0.1 mmol/kg), standard food (0.5 g), sodium nitroprusside, a nitric oxide donor (5 mg/kg), and haemoglobin, a nitric oxide scavenger (150 mg/kg) given either with water or KNO3. RESULTS In controls, the fall in blood pressure increased from 7.8 +/- 2.0 to 31.6 +/- 2. 7 mmHg at distending pressures from 10 to 40 mmHg, respectively. KNO3 significantly reduced the amplitude of blood pressure response for the highest distending pressures (35 and 40 mmHg), while KCl induced a reduction in blood pressure response at all gastric pressures. NaNO3 and NaCl did not induce significant changes in distension-induced depressor responses. Administration of 0.5 g of standard food or sodium nitroprusside reproduced the effect of KNO3, which was reversed by haemoglobin. None of the compounds modified the gastric pressure-volume relationship, except KNO3, which increased gastric volume for the lowest distending pressures, and haemoglobin, which reduced the volume for the highest pressure. CONCLUSIONS Ingestion of potassium nitrate reduces the sensitivity to gastric distension, through a mechanism involving nitric oxide.
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Affiliation(s)
- M L Rouzade
- Neuro-Gastroenterology & Nutrition Unit, Institut National de la Recherche Agronomique, Toulouse, France
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Gangolli SD, van den Brandt PA, Feron VJ, Janzowsky C, Koeman JH, Speijers GJ, Spiegelhalder B, Walker R, Wisnok JS. Nitrate, nitrite and N-nitroso compounds. Eur J Pharmacol 1994; 292:1-38. [PMID: 7867685 DOI: 10.1016/0926-6917(94)90022-1] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A risk assessment has been made on nitrate, nitrite and N-nitroso compounds encountered in the human diet. Vegetables constitute a major source of nitrate providing over 85% of the average daily human dietary intake. Nitrite and N-nitroso compounds present in the diet contribute relatively small amounts to the body burden and the major source of these biologically reactive compounds is derived from the bacterial and mammalian metabolism of ingested nitrate. Additionally, endogenous synthesis provides an important source contributing to the body burden of nitrate. Data from animal toxicological studies, human effects and epidemiological surveys have been reviewed and evaluated. It is concluded that there is no firm scientific evidence at present to recommend drastic reductions beyond the average levels of nitrate encountered in vegetables grown in keeping with good agricultural practice. Recommendations have also been made for further animal and human studies to be carried out to elucidate the potential risks to man from ingested nitrate.
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12
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Phillips BJ, Tee AC, Carroll PA, Purchase R, Walters DG. Toxicity to Chinese hamster ovary (CHO) cells of the products of reaction of butylated hydroxyanisole with nitrite at low pH. Toxicol In Vitro 1994; 8:117-23. [PMID: 20692896 DOI: 10.1016/0887-2333(94)90215-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/1993] [Indexed: 11/16/2022]
Abstract
Butylated hydroxyanisole (BHA) was found to react readily with nitrite in acidified physiological saline. With low concentrations of reactants at pH 2, HPLC analysis demonstrated the formation of two products, tert-butylquinone (BQ) and a second, unidentified compound. Neutralized BHA/nitrite reaction mixtures were highly toxic to cultured Chinese hamster ovary (CHO) cells. At non-lethal concentrations, causing some cell cycle delay, there was a statistically significant but variable induction of endoreduplication and tetraploidy and a very weak induction of chromosome breakage. The effects were similar to those of pure BQ. It is suggested that the formation of toxic products from BHA, by an oxidative reaction such as that described with nitrite, might be involved in the mechanism of BHA carcinogenesis in the rat forestomach.
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Affiliation(s)
- B J Phillips
- BIBRA Toxicology International, Woodmansterne Road, Carshalton, Surrey SM5 4DS, UK
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13
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Affiliation(s)
- L Vittozzi
- Biochemical Toxicology Unit, Istituto Superiore di Sanità, Roma, Italy
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14
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Melarange R, Moore G, Blower PR, Coates ME, Ward FW, Ronaasen V. A comparison of indomethacin with ibuprofen on gastrointestinal mucosal integrity in conventional and germ-free rats. Aliment Pharmacol Ther 1992; 6:67-77. [PMID: 1543817 DOI: 10.1111/j.1365-2036.1992.tb00546.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effects of indomethacin and ibuprofen on gastrointestinal mucosal integrity were studied in conventional and germ-free rats. Only ibuprofen induced significant gastric erosion formation in both conventional and germ-free animals, demonstrating that the presence of micro-organisms is not required in this form of damage. Both indomethacin and ibuprofen caused significant intestinal damage and blood loss in germ-free animals. However, in the conventional counterparts, damage due to indomethacin was enhanced whereas that induced by ibuprofen was not. The results from the present work would suggest that non-steroidal anti-inflammatory drugs such as indomethacin, which are secreted largely in the bile, unlike ibuprofen, may act in concert with bacteria and the constituents of bile to induce, in part, intestinal damage and blood loss.
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Affiliation(s)
- R Melarange
- SmithKline Beecham Pharmaceuticals, Harlow Essex, UK
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15
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Chadwick RW, George SE, Claxton LD. Role of the gastrointestinal mucosa and microflora in the bioactivation of dietary and environmental mutagens or carcinogens. Drug Metab Rev 1992; 24:425-92. [PMID: 1289035 DOI: 10.3109/03602539208996302] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- R W Chadwick
- USEPA Environmental Research Center, Health Effects Research Lab, Research Triangle Park, North Carolina 27711
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16
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Sandler M, Przyborowska A, Halket J, Watkins P, Glover V, Coates ME. Urinary but not brain isatin levels are reduced in germ-free rats. J Neurochem 1991; 57:1074-5. [PMID: 1861145 DOI: 10.1111/j.1471-4159.1991.tb08259.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Germ-free rats excreted considerably smaller amounts of the monoamine oxidase-inhibiting compound isatin than the substantially larger output by conventional animals of the same strain, although concentrations in brain and other tissues were similar in the two groups. Thus, isatin is likely to be elaborated both endogenously in rat tissues and "exogenously" by flora inhabiting the lumen of the alimentary tract.
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Affiliation(s)
- M Sandler
- Department of Chemical Pathology, Queen Charlotte's & Chelsea Hospital, London, UK
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17
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Kälble T, Tricker AR, Berger M, Amelung F, Waldherr R, Hothorn L, Möhring K, Staehler G. Tumor induction in a rat model for ureterosigmoidostomy without evidence of nitrosamine formation. J Urol 1991; 146:862-6. [PMID: 1714971 DOI: 10.1016/s0022-5347(17)37949-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Twenty rats were randomized into a vesicosigmoidostomy and an unoperated control group. In both groups the 24 hour excretion of secondary amines, nitrate, nitrite and nitrosamines was measured before and after gavage of proline and nitrate, piperazine and nitrate, N-nitrosoproline, mono-N-nitrosopiperazine. The urinary nitrosamine concentrations were not significantly different between both groups neither before nor after application of the several substances. Thirty rats were randomized into two vesicosigmoidostomy groups with and without antibiotic coverage and an unoperated control group. After ligation of distal rectum and mesosigmoid the rectosigmoids were removed. No significant concentrations of volatile nitrosamines could be measured in the rectosigmoid contents of the three groups. One hundred and twenty rats randomized into three groups following vesicosigmoidostomy received the potential nitrosamine antidotes sodium-2-mercaptoethane sulfonate or sodiumpentosan-polysulfate or acted as controls. 12/118 (10.2%) developed adenomas and 25/118 (21.2%) adenocarcinomas at the vesico-colonic anastomosis with no significant differences between the three groups concerning tumor incidence or mortality. The results show that colon carcinomas occur in a rat model for ureterosigmoidostomy without evidence for thus induced nitrosamine formation. This and the missing effect of nitrosamine antidotes suggest that other factors than nitrosation must be responsible for colon carcinogenesis following urinary diversion via intestine.
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Affiliation(s)
- T Kälble
- Department of Urology, University of Heidelberg, Germany
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18
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Nielsch AS, Ward FW, Coates ME, Walker R, Rowland IR. Influence of dietary protein and gut microflora on endogenous synthesis of nitrate induced by bacterial endotoxin in the rat. Food Chem Toxicol 1991; 29:387-90. [PMID: 1874466 DOI: 10.1016/0278-6915(91)90078-l] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Germ-free (GF) rats were maintained on a diet marginally adequate in protein, with and without a supplement of NH4Cl. Their urinary excretion of total nitrogen, nitrate, urea and creatinine was measured before and for 4 days after injection of Escherichia coli endotoxin (lipopolysaccharide; LPS). Although more nitrogen was excreted by rats on the diet supplemented with NH4Cl, nitrate excretion was increased to a similar extent in rats on both diets. This suggests that oxidation of ammonia released by deamination of amino acids is an unlikely pathway of nitrate synthesis. In a second experiment, nitrate excretion before and after injection of LPS was measured in GF and conventional (CV) rats given high- or low-protein diets. Urinary 3-methylhistidine (3MH) was measured as an index of breakdown of tissue protein. In both environments, nitrate excretion was significantly greater, before and after LPS administration, by rats on the high-protein diet than by their counterparts on the low-protein diet, and was generally greater by GF than by CV rats. Since only small, non-significant rises in urinary 3MH were observed after LPS treatment, it was concluded that the bulk of the nitrogen required for nitrate synthesis in response to endotoxin is derived from dietary protein rather than from nitrogenous products of tissue breakdown.
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Affiliation(s)
- A S Nielsch
- Robens Institute, University of Surrey, Guildford, UK
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19
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Walker R. Nitrates, nitrites and N-nitrosocompounds: a review of the occurrence in food and diet and the toxicological implications. FOOD ADDITIVES AND CONTAMINANTS 1990; 7:717-68. [PMID: 2079111 DOI: 10.1080/02652039009373938] [Citation(s) in RCA: 274] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Data on occurrence of nitrate, nitrite and N-nitrosocompounds in food and drinking water, and on total dietary intakes are reviewed. Metabolic, toxicological and epidemiological studies are surveyed and the implications with respect to safety evaluation are addressed. It is concluded that, on the basis of recent long-term animal studies and of clinical experience in man, the current Acceptable Daily Intake (ADI) allocated to nitrate by the Joint FAO/WHO Expert Committee on Food Additives of 0-5 mg/kg body weight/day (expressed as sodium nitrate) might be increased to 0-25 mg/kg body weight/day. Based on similar criteria, the ADI for nitrite would be 0-0.1 mg/kg body weight/day (expressed as sodium nitrite). In view of the known carcinogenicity of N-nitrosocompounds, exposure to these compounds in food should be minimized by appropriate technological means, such as lowering the nitrite concentration in preserved foods to the minimum required to ensure microbiological safety and use of inhibitors of nitrosation like alpha-tocopherol or ascorbic acid. Further work is needed to define the minimal levels of nitrite in foods needed to inhibit outgrowth of Clostridium botulinum and toxin production.
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Affiliation(s)
- R Walker
- Department of Biochemistry, University of Surrey, Guildford, UK
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20
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Ward FW, Coates ME, Cole CB, Fuller R. Effect of dietary fats on endogenous formation of N-nitrosamines from nitrate in germ-free and conventional rats and rats harbouring a human flora. FOOD ADDITIVES AND CONTAMINANTS 1990; 7:597-604. [PMID: 2253804 DOI: 10.1080/02652039009373925] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Urinary excretion of N-nitrosoproline (NPRO) was measured in groups of four germ-free (GF) and conventional (CV) rats given a purified diet with or without inclusion of 100 g butterfat, coconut oil or maize oil/kg, and drinking water containing 0.235 M-NaNO3. In the CV environment rats given the fat-supplemented diets excreted significantly less NPRO than those on the low-fat diet. No corresponding decrease in NPRO excretion occurred in the GF environment. Nitrate reductase activity was measured in stomach contents and homogenates of stomach tissue from GF and CV rats given the different diets. No activity was detected in any of the contents from GF rats. Nitrate reductase activity was significantly reduced in contents from all the CV rats given the fat-supplemented diets, the effect being most marked in those given butterfat. Activity was much lower in tissue homogenates from GF rats than in those from their CV counterparts, but was not affected by diet in either environment. Groups of four CV rats, or rats harbouring a human faecal flora (HF), were given the purified diet with or without addition of 100 g butterfat or maize oil/kg and drinking water containing 0.235 M-NaNO3. All groups given the fat-supplemented diet with the exception of the HF rats given butterfat. It is concluded that the reduced excretion of NPRO by rats given diets containing fat was mainly due to inhibition of microbial nitrate reductase activity in the foregut. The smaller effect of butterfat on the HF rats accords with earlier findings in human subjects.
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Affiliation(s)
- F W Ward
- Robens Institute, University of Surrey, Guildford, UK
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21
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Kälble T, Tricker AR, Möhring K, Berger MR, Geiss H, Staehler G. The role of nitrate, nitrite and N-nitrosamines in carcinogenesis of colon tumours following ureterosigmoidostomy. UROLOGICAL RESEARCH 1990; 18:123-9. [PMID: 2339481 DOI: 10.1007/bf00302472] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Urinary diversion in both a rat model for ureterosigmoidostomy and in ureterosigmoidostomy patients result in an increased incidence of colon tumours. Bacterial and chemical investigations on feces-urine mixtures from both the rat model and ureterosigmoidostomy patients showed the presence of a complex nitrate-reducing bacterial flora in both rats and humans. This bacterial flora actively reduced urinary nitrate to nitrite in humans and increased the endogenous formation of N-nitroso compounds. No evidence of urinary nitrate reduction and increased nitrosamine formation in the rectosigmoid of rats was found. The results support the N-nitrosamine theory of carcinogenesis of the colon following ureterosigmoidostomy in humans, but not in rats. As the rat model induces colon carcinomas, factors other than the increased endogenous formation of N-nitroso compounds in the rectosigmoid may contribute to the initiation of colon carcinomas following ureterosigmoidostomy.
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Affiliation(s)
- T Kälble
- Urological Department, University of Heidelberg, FRG
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22
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Ilett KF, Tee LB, Reeves PT, Minchin RF. Metabolism of drugs and other xenobiotics in the gut lumen and wall. Pharmacol Ther 1990; 46:67-93. [PMID: 2181492 DOI: 10.1016/0163-7258(90)90036-2] [Citation(s) in RCA: 125] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Metabolism in the gut lumen and wall can decrease the bioavailability and the pharmacological effects of a wide variety of drugs. Bacterial flora in the gut, the environmental pH and oxidative or conjugative enzymes present in the intestinal epithelial cells can all contribute to the process. Bacterial biotransformation is greatest in the colon, while gut wall metabolism is generally highest in the jejunum and decreases distally. Gut wall metabolism may be induced or inhibited by dietary or environmental xenobiotics or by co-administered drugs. Recent evidence suggests that some drugs, food-derived mutagens and other xenobiotics can be metabolized by gut flora and/or gut wall enzymes to reactive species which may cause tumors.
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Affiliation(s)
- K F Ilett
- Department of Pharmacology, University of Western Australia, Nedlands
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23
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Ward FW, Coates ME, Walker R. Influence of dietary protein and gut microflora on endogenous synthesis of nitrate and N-nitrosamines in the rat. Food Chem Toxicol 1989; 27:445-9. [PMID: 2777148 DOI: 10.1016/0278-6915(89)90030-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Groups of four germ-free (GF) and conventional (CV) rats were given purified diets containing either 50 or 200 g lactalbumin/kg for 2 wk and their urinary excretion of nitrate was measured. Urinary excretion of N-nitrosoproline was also measured in one of the three experiments. Both GF and CV rats given the high-protein diet excreted significantly more nitrate and N-nitrosoproline than those given the low-protein diet. On both diets GF rats excreted more nitrate than their CV counterparts but N-nitrosoproline excretion was not affected by environment. Groups of 11 GF and CV rats given diets containing sesame meal with or without a supplement of lysine-HCl for 2 wk, excreted similar amounts of nitrate on both diets, but more nitrate was excreted by GF rats than by their CV counterparts. N-nitrosoproline excretion by rats given the lysine supplement was higher in both environments. It is concluded that endogenous synthesis of nitrate is mediated by mammalian tissues rather than microflora and that dietary protein is an important source of nitrogen for the synthesis, although surplus amino acids from an imbalanced protein source do not act as precursors of endogenously formed nitrate. Some of the synthesized nitrate or its precursors appears to be metabolized by the microflora in the CV rat.
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Affiliation(s)
- F W Ward
- Robens Institute, University of Surrey, UK
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24
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Massey RC, Key PE, Mallett AK, Rowland IR. An investigation of the endogenous formation of apparent total N-nitroso compounds in conventional microflora and germ-free rats. Food Chem Toxicol 1988; 26:595-600. [PMID: 3181835 DOI: 10.1016/0278-6915(88)90230-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The endogenous formation of apparent total N-nitroso compounds (ATNC) has been investigated in germ-free (GF) and conventional (CV) microflora rats as a function of the drinking-water nitrate concentration. ATNC levels were below the 40 micrograms (N-NO)/kg detection limit in the blood, liver, kidney, spleen and small intestine of all CV and GF rats. For the CV rats ATNC were detected in concentrations of up to 370 micrograms (N-NO)/kg in the large intestine and up to 50 micrograms (N-NO)/kg in the stomach and there was a significant positive correlation between ATNC formation and the drinking-water nitrate level. Comparison of these results with those from GF rats showed that the ATNC in the stomach and large intestine of the CV animals were formed by microbial action, most probably involving bacterial nitrate-reductase activity.
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Affiliation(s)
- R C Massey
- Ministry of Agriculture, Fisheries and Food, Food Science Division, Norwich
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25
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Abstract
1. The metabolic activity of the gastrointestinal microflora can be modified by numerous factors derived from the host, the host's environment, and the flora itself. 2. Marked differences exist in microbial composition and metabolism of the gut floras of different species of animal, and in the degree of colonization of the various regions of the gut. 3. The microbial flora changes with age, particularly in early infancy, and developmental changes in in vivo metabolism attributable to the gut flora have been noted for methylmercury. 4. Gastrointestinal disease can have a profound effect on microbial colonization and metabolism in the upper regions of the human gut. In particular, hypochlorhydria can lead to elevation in bacterial numbers, and nitrite and nitrosamine concentrations in gastric juice. 5. Environmental factors such as drugs (particularly antibiotics), diet, and xenobiotics can modify microbial metabolism and toxicity of foreign compounds. In some cases exposure to xenobiotics (e.g., cyclamate, rutin) results in metabolic adaptation and increased biotransformation of the foreign compound. 6. By their fermentation of dietary residues and endogenous carbohydrates, the gut bacteria produce acids which can lower lumenal pH and, in turn, modify bacterial enzyme activities. However, the changes in activity appear to be enzyme specific, some increasing with pH and others being inversely related to pH of incubation.
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26
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Abstract
1. Groups of four conventional (CV) rats ate natural or purified diets either with or without 100 g fat/kg and drank 0.235 M-sodium nitrate. The fats tested were butterfat, coconut oil, olive oil, maize oil and safflower oil. 2. Decreased urinary excretion of N-nitrosoproline (NPRO) was observed in rats fed on fat-supplemented diets compared with those fed on low-fat diets, with butterfat having the greatest effect of the fats tested. 3. Reduced excretion of NPRO was not the result of inhibition of the intragastric N-nitrosation reaction or absorption of nitrosamine from the gastrointestinal tract. 4. The availability of nitrite in aqueous solution was decreased by the fat diets but the effect was similar in all the fats tested. 5. Nitrate reductase activity was present in the forestomach contents of CV rats at pH greater than 4 and was apparently inhibited by feeding a fat diet. No nitrate reductase activity was detected in stomach contents of germ-free rats. 6. Nitrate reductase activity in stomach and small intestinal tissue was not altered by feeding a fat diet. 7. It was concluded that nitrate reductase activity in stomach contents was of microbial origin and the decreased urinary excretion of NPRO on feeding the fat diets was mainly due to the inhibition of nitrate reductase activity in stomach contents.
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Affiliation(s)
- F W Ward
- Robens Institute, University of Surrey, Guildford
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