Life Sciences, Vol. 51, pp. 1333-1337 Printed in the USA
Pergamon Press
ALCOHOL DEHYDROGENASE MEDIATED ACETALDEHYDE PRODUCTION BY
HELICOBACTER PYLORI - A POSSIBLE MECHANISM BEHIND GASTRIC INJURY Risto P. Roine *, Katja S. Salmela', Johanna H/56k-Nikanne 2, Timo U. Kosunen2, and Mikko Salaspuro *. 1Research Unit of Alcohol Diseases and 2Department of Bacteriology and Immunology, University of Helsinki, 00290 Helsinki, Finland. (Received in final form August 21, 1992)
Summary Two standard Helicobacter pylori strains showed significant cytosolic alcohol dehydrogenase activity and produced considerable amounts of acetaldehyde when incubated with an ethanol containing solution in vitro. The alcohol dehydrogenase activity of the Helicobacter pylori strains was almost as high as that found in Klebsiella pneumoniae and far greater than that in Escherichia coli or Campylobacterjejuni. The amount of acetaldehyde produced by cytosol prepared from Helicobacter pylori exceeded that by any of the other bacteria studied. The bacterial production of acetaldehyde - a highly toxic and reactive substance - could be an important factor in the pathogenesis of Helicobacterpylori associated gastric injury and increased risk of gastric cancer. Several bacteria are known to exhibit alcohol dehydrogenase (ADH) activity (1). Consequently, they are capable of fermenting different sugars to ethanol and, if the reaction runs in the opposite direction, of producing acetaldehyde from endogenous or exogenous ethanol. Fermentation of sugars to ethanol is a common source of anaerobic energy for ethanologenic bacteria, and bacterial ethanol production has been shown to occur in the intestine of both humans (2) and experimental animals (3,4). Acetaldehyde, the first metabolite of ethanol oxidation, is a highly reactive and toxic substance. It forms readily adducts with different cellular proteins and may also induce lipid peroxidation, both of which can lead to tissue injury (5). Acetaldehyde produced by bacteria has recently also been incriminated as a possible pathogenetic factor in alcohol associated rectal carcinogenesis (6) and cancer of the upper respiratory tract (7).
Helicobacter pylori is accepted as the major cause of type B gastritis which is strongly associated with duodenal and gastric ulcer disease (8). Furthermore, Helicobacter pylori infection has a large prevalence in healthy asymptomatie populations (9), and recent evidence has linked it with the occurrence of gastric cancer (10-12). The pathogenetic mechanisms behind Helicobacter pylori associated morbidity have, however, so far not been fully elucidated. The existence of gastric mucosal ADH activity and gastric alcohol metabolism is well established (13, 14). It is, however, not known whether Helicobacterpylori could be partly responsible for Address reprint requests to Dr. M. Salaspuro, Research Unit of Alcohol Diseases, Tukholmankatu 8 F, 00290 Hdsinki, Finland. 0024-3205/92 $5.00 + .00 Copyright © 1992 Pergamon Press Ltd All rights reserved.
1334
Acetaldehyde by Helicobacter pylori
Vol. 51, No. 17, 1992
this gastric oxidation of alcohol. The aim of the present study was, therefore, to establish the possible presence of cytosolic ADH in Helicobacter pylori and to determine whether this activity could be capable of producing acetaldehyde in amounts sufficient to be at least theoretically responsible for tissue injury. Materials and methods
Helicobacter pylori were grown on brucella agar plates (BBL, Cockeysville, MD, USA) supplemented with whole horse blood (7%) in an atmosphere of 5% 0z, 10% CO2, and 85% N 2 at 35°C for 48 h. The cultured bacteria (strains NCTC 11637 and NCTC 11638) were first washed twice in 100 mM potassium phosphate buffer and then sonicated in the same buffer solution. This was followed by centrifugation of the sonicate at 100 000 g at 5°C for 60 minutes to obtain cytosol. Cytosolic ADH activity was then determined spectrophotometrically using approximately 50-200/~g cytosolic protein and by measuring, after addition of ethanol, the reduction of nicotine amide dinucleotide (NAD, final concentration in the reaction mixture 2.5 mM) to its reduced form (NADH) at 25°C in 0.1 M glycine buffer with a pH of 9.6. Seven ethanol concentrations ranging from 12.5 mM to 2.5 M were used. Protein concentration of the bacterial cytosols was determined by the Lowry method (15), and ADH activity was expressed as nmoles of NADH produced by mg bacterial cytosolic protein per minute. Values for I ~ (Michaelis constant) were determined from Lineweaver-Burk plots with a computerized dataanalysis program. The ability of Helicobacter pylori to produce acetaldehyde in vitro was determined by incubating 0.25 ml of the cytosol (prepared as described above) in closed vials with an equal amount of 1% (w/v) ethanol in saline containing NAD (final ethanol concentration in the vials 0.11 M, final NAD concentration 3.0 mM, pH 7.3) for 18 h at 37°C. After the incubation period the vials were rapidly frozen and kept at -20°C until ethanol and acetaldehyde concentrations were determined using head space gas chromatography by heating the vials to a temperature of 37°C as suggested earlier (16). Conditions for analysis were following: Column 60/80 Carbopack C/0.2% Carbowax 1500, 2m x 1/8" ID (Supelco Inc, Bellefonte, PA, USA); oven temperature, 75°(2; dosing line detector temperature, 200°C; carrier gas (N2) flow, 20 ml/min. In order to compare ADH activity observed in Helicobacterpylori to that of other bacteria, we cultured in a similar manner three other bacteria (Escherichia coli ATCC 25922, Campylobacterjejuni CCUG 10937, and Klebsiellapneumoniae ATCC 138831). Cytosols from these bacteria were prepared and used for analysis in analogy with the procedure described above. Results Cytosols of both Helicobacterpylori strains showed significant ADH activity both at low and high ethanol concentrations (Table I). The K~ of bacterial ADH from Helicobacter pylori for ethanol was found to be 103 mM for strain NCTC 11637 and 69 mM for strain NCTC 11638. The mean ADH activity of both Helicobacterpylori strains was more than ten-fold higher than that found in Escherichia coli and Campylobacter jejuni. Klebsiella pneumoniae, by contrast, showed a somewhat higher mean ADH activity than observed in the two helicobacter strains. Cytosols from both standard Helicobacter pylori strains produced significant amounts of acetaldehyde (Fig. 1). In line with the observed ADH activity, also the amount of acetaldehyde produced by the helicobacter strains was larger than that produced by the cytosols prepared
Acetaldehyde by Helicobacter pylori
Vol. 51, No. 17, 1992
1335
TABLE I
ETHANOL CONCENTRATION 12.5 mM
26mM
50mM
O.6M
1.OM
1.6M
2.6M
NCTC 11637
13±1
24±2
38±1
104±6
111 ± 6
116±8
111 ±7
NCTC 11638
18±2
33±3
56±3
128±10
119±9
111+10
81±6
HELICOSACTER STRAINS
OTHER BACTERIA
Escherichia coil
1,5±O.2
1,4±O.2
1,6±0.3
1.3±O.4
2.3+0.4
3.9±0.3
7.0±0.3
Carnpylobacter jejuni
O.2±O.1
0,5±0.3
1.2±0.2
4.1 ¢0.3
4.5±0.3
4.7+0,4
5.2±0.4
Klebsiella pneumoniae
166±27
169±22
190±23
220+36
280±48
290±72
252±86
In vitro ADH activities (mean +SE) expressed as nmol NADH/mg protein/min in two Helicobacterpyloristrains and in three other bacteria (Escherichia coil, Campylobacter jejuni, and Klebsiella pneumoniae). The results in each case are based on three to four separate cultures. ADH activity was determined with seven different ethanol concentrations.
from Escherichia coli or Campylobacterjejuni. By contrast, the amount of acetaldehyde found after incubation of cytosol prepared from Klebsiella pneumoniae with an ethanol containing solution was almost undetectable (Fig. 1).
=
4
Q.
w o
3-
E
2-
T T 0
NCTC 11637
NCTC 11638
I
t
E. coil
--
C. jejuni
K. pneumoniae
FIG. 1 A c e t a l d e h y d e production (mean + SE) expressed as pmol acetaldehyde p r o d u c e d / m g bacterial protein during an 18 h incubation by t w o Helicobacter pylori strains (NCTC 1 1 6 3 7 and NCTC 1 1 6 3 8 ) and by three other bacteria (Escherichia co~i, Campylobacter jejuni, and Klebsiella pneurnoniae). The results in each case are based on three separate cultures and acetaldehyde determinations.
1336
Acetaldehyde by Helicobacter pylori
Vol. 51, No. 17, 1992
Discussion Earlier studies have suggested that ammonia produced by Helicobacter pylori may play a pathogenetic role in Helicobacter pylori associated gastric injury (17). Our results show that Helicobacter pylori exhibits significant ADH activity which is associated with a high capacity to produce acetaldehyde in vitro. If this occurs also in vivo, bacterial acetaldehyde production may be a significant factor in the pathogenesis of Helicobacter pylori associated gastritis. Acetaldehyde, whether produced as an intermediate compound during bacterial fermentation of sugars to ethanol or as an oxidation product of endogenous or exogenous ethanol, could lead to the formation of acetaldehyde adducts with gastric mucus or mucosal proteins of the gastric epithelial cells in analogy to the adduct formation with hepatic proteins in the liver. This adduct formation and/or acetaldehyde mediated lipid peroxidation could be important risk factors for the development of gastric injury and cancer. Mean ADH activity observed in Helicobacter pylori at the ethanol concentrations likely to occur in the stomach after drinking of alcoholic beverages was more than 20 times higher than that we have found in histologically normal human gastric mucosal biopsy samples taken from the body of the stomach. In comparison to the other bacteria studied, cytosol from Klebsiella pneumoniae possessed even greater ADH activity. Despite this, acetaldehyde was virtually undetectable after incubation of cytosol from Klebsiella pneumoniae with an ethanol containing solution. This indicates that Klebsiella pneumoniae has an ability to rapidly convert acetaldehyde into some other compound. Acetate would be the most obvious choice if the bacteria contained also aldehyde dehydrogenase. Our preliminary experiments, however, did not detect any accumulation of acetate in the vials containing cytosol from Klebsiella pneumoniae. Thus, some other of the many pathways reported to be active in bacterial metabolism of ethanol and related compounds may be responsible for the rapid removal of acetaldehyde in Klebsiella pneumoniae. By virtue of possessing ADH activity, Helicobacter pylori could also contribute to the ethanol oxidation shown to occur in the stomach by gastric mucosal ADH activity (13,14). Differences in the infection status with Helicobacterpylori could, consequently, partly explain the interindividual differences observed in the magnitude of gastric ethanol oxidation. This possibility, however, needs to be established in future studies. Acknowledgements The skillful technical assistance of Ms. Eila Kelo and Ms. Leena-Riitta Korhonen is gratefully acknowledged. The work was supported by grants from the Yrj6 Jahnsson Foundation and Foundation of Gastric Diseases, Helsinki, Finland. References 1. 2. 3. 4. 5.
R.J. LAMED and J.G. ZEIKUS, Biochem J 19_.__55183-190(1981). J.C. BODE, S. RUST and C. BODE, Scand J Gastroentero119 853-856 (1984). H.A. KREBS and J.R. PERKINS, Biochem J 118635-644 (1970). E. BARAONA, R. JULKUNEN, L. TANNENBAUM and C.S. LIEBER, Gastroenterology 90103-110 (1986). M. SALASPURO and K. LINDROS, Alcohol-Related Diseases in Gastroenterology, H.K. Seitz and B. KommereU (eds), 106-123, Springer Verlag, Berlin, Heidelberg, New York, Tokyo (1985).
Vol. 51, No. 17, 1992
6. 7. 8. 9. 10. 11.
12. 13. 14. 15. 16. 17.
Acetaldehyde by Helicobacter pylori
1337
H.K. SEITZ, U.A. SIMANOWSKI, F.T. GARZON, J.M. RIDEOUT, T.J. PETERS, A. KOCH, M.R. BERGER, H. EINECKE and M. MAIWALD, Gastroenterology 98 406413 (1990). H. MIYAKAWA, E. BARAONA, J.C. CHANG, M.D. LESSER and C.S. LIEBER, Alcohol: Clin Exp Res 10 517-520 (1986). D.Y. GRAHAM, Gastroenterology 96 (Suppl) 615-625 (1989). T.U. KOSUNEN, J. HOOK, H. RAUTELIN and G. MYLLYLA, Scand J Gastroenterol 24 110-114 (1989). A. NOMURA, G.N. STEMMERMAN, P.-H. CHYOU, I. KATO, G.I. PEREZ-PEREZ and M.J. BLASER, N Engl J Meal 325 1132-1136 (1991). J. PARSONNET, G.D. FRIEDMAN, D.P. VANDERSTEEN, Y. CHANG, J.H. VOGELMAN, N. ORENTREICH and R.K. SIBLEY, N Engl J Med 325 1127-1131 (1991). P. SIPPONEN, T.U. KOSUNEN, J. VALLE, M. RIIHEL,~ and K. SEPP/~L,~, J Clin Pathol, in press. Y. LAMBOEUF, G. DE SAINT BLANQUAT and R. DERACHE, Biochem Pharmacol 39 542-545 (1981). R.J.K. JULKUNEN, L. TANNENBAUM, E. BARAONA and C.S. LIEBER, Alcohol 2 437-441 (1985). O.H. LOWRY, N.J. ROSEBROUGH, A.L. FARR and R.J. RANDALL, J Biol Chem 193 262-75 (1951). P. PIKKARAINEN, M. SALASPURO and C.S. LIEBER, Alcoholism: Clin Exp Res 3 259-261 (1979). A.T. TRIEBLING, M.A. KORSTEN, J.W. DLUGOSZ, F. PARONETTO and C.S. LIEBER, Dig Dis Sci 3_661089-1096 (1991).
Pergamon Press
ALCOHOL DEHYDROGENASE MEDIATED ACETALDEHYDE PRODUCTION BY
HELICOBACTER PYLORI - A POSSIBLE MECHANISM BEHIND GASTRIC INJURY Risto P. Roine *, Katja S. Salmela', Johanna H/56k-Nikanne 2, Timo U. Kosunen2, and Mikko Salaspuro *. 1Research Unit of Alcohol Diseases and 2Department of Bacteriology and Immunology, University of Helsinki, 00290 Helsinki, Finland. (Received in final form August 21, 1992)
Summary Two standard Helicobacter pylori strains showed significant cytosolic alcohol dehydrogenase activity and produced considerable amounts of acetaldehyde when incubated with an ethanol containing solution in vitro. The alcohol dehydrogenase activity of the Helicobacter pylori strains was almost as high as that found in Klebsiella pneumoniae and far greater than that in Escherichia coli or Campylobacterjejuni. The amount of acetaldehyde produced by cytosol prepared from Helicobacter pylori exceeded that by any of the other bacteria studied. The bacterial production of acetaldehyde - a highly toxic and reactive substance - could be an important factor in the pathogenesis of Helicobacterpylori associated gastric injury and increased risk of gastric cancer. Several bacteria are known to exhibit alcohol dehydrogenase (ADH) activity (1). Consequently, they are capable of fermenting different sugars to ethanol and, if the reaction runs in the opposite direction, of producing acetaldehyde from endogenous or exogenous ethanol. Fermentation of sugars to ethanol is a common source of anaerobic energy for ethanologenic bacteria, and bacterial ethanol production has been shown to occur in the intestine of both humans (2) and experimental animals (3,4). Acetaldehyde, the first metabolite of ethanol oxidation, is a highly reactive and toxic substance. It forms readily adducts with different cellular proteins and may also induce lipid peroxidation, both of which can lead to tissue injury (5). Acetaldehyde produced by bacteria has recently also been incriminated as a possible pathogenetic factor in alcohol associated rectal carcinogenesis (6) and cancer of the upper respiratory tract (7).
Helicobacter pylori is accepted as the major cause of type B gastritis which is strongly associated with duodenal and gastric ulcer disease (8). Furthermore, Helicobacter pylori infection has a large prevalence in healthy asymptomatie populations (9), and recent evidence has linked it with the occurrence of gastric cancer (10-12). The pathogenetic mechanisms behind Helicobacter pylori associated morbidity have, however, so far not been fully elucidated. The existence of gastric mucosal ADH activity and gastric alcohol metabolism is well established (13, 14). It is, however, not known whether Helicobacterpylori could be partly responsible for Address reprint requests to Dr. M. Salaspuro, Research Unit of Alcohol Diseases, Tukholmankatu 8 F, 00290 Hdsinki, Finland. 0024-3205/92 $5.00 + .00 Copyright © 1992 Pergamon Press Ltd All rights reserved.
1334
Acetaldehyde by Helicobacter pylori
Vol. 51, No. 17, 1992
this gastric oxidation of alcohol. The aim of the present study was, therefore, to establish the possible presence of cytosolic ADH in Helicobacter pylori and to determine whether this activity could be capable of producing acetaldehyde in amounts sufficient to be at least theoretically responsible for tissue injury. Materials and methods
Helicobacter pylori were grown on brucella agar plates (BBL, Cockeysville, MD, USA) supplemented with whole horse blood (7%) in an atmosphere of 5% 0z, 10% CO2, and 85% N 2 at 35°C for 48 h. The cultured bacteria (strains NCTC 11637 and NCTC 11638) were first washed twice in 100 mM potassium phosphate buffer and then sonicated in the same buffer solution. This was followed by centrifugation of the sonicate at 100 000 g at 5°C for 60 minutes to obtain cytosol. Cytosolic ADH activity was then determined spectrophotometrically using approximately 50-200/~g cytosolic protein and by measuring, after addition of ethanol, the reduction of nicotine amide dinucleotide (NAD, final concentration in the reaction mixture 2.5 mM) to its reduced form (NADH) at 25°C in 0.1 M glycine buffer with a pH of 9.6. Seven ethanol concentrations ranging from 12.5 mM to 2.5 M were used. Protein concentration of the bacterial cytosols was determined by the Lowry method (15), and ADH activity was expressed as nmoles of NADH produced by mg bacterial cytosolic protein per minute. Values for I ~ (Michaelis constant) were determined from Lineweaver-Burk plots with a computerized dataanalysis program. The ability of Helicobacter pylori to produce acetaldehyde in vitro was determined by incubating 0.25 ml of the cytosol (prepared as described above) in closed vials with an equal amount of 1% (w/v) ethanol in saline containing NAD (final ethanol concentration in the vials 0.11 M, final NAD concentration 3.0 mM, pH 7.3) for 18 h at 37°C. After the incubation period the vials were rapidly frozen and kept at -20°C until ethanol and acetaldehyde concentrations were determined using head space gas chromatography by heating the vials to a temperature of 37°C as suggested earlier (16). Conditions for analysis were following: Column 60/80 Carbopack C/0.2% Carbowax 1500, 2m x 1/8" ID (Supelco Inc, Bellefonte, PA, USA); oven temperature, 75°(2; dosing line detector temperature, 200°C; carrier gas (N2) flow, 20 ml/min. In order to compare ADH activity observed in Helicobacterpylori to that of other bacteria, we cultured in a similar manner three other bacteria (Escherichia coli ATCC 25922, Campylobacterjejuni CCUG 10937, and Klebsiellapneumoniae ATCC 138831). Cytosols from these bacteria were prepared and used for analysis in analogy with the procedure described above. Results Cytosols of both Helicobacterpylori strains showed significant ADH activity both at low and high ethanol concentrations (Table I). The K~ of bacterial ADH from Helicobacter pylori for ethanol was found to be 103 mM for strain NCTC 11637 and 69 mM for strain NCTC 11638. The mean ADH activity of both Helicobacterpylori strains was more than ten-fold higher than that found in Escherichia coli and Campylobacter jejuni. Klebsiella pneumoniae, by contrast, showed a somewhat higher mean ADH activity than observed in the two helicobacter strains. Cytosols from both standard Helicobacter pylori strains produced significant amounts of acetaldehyde (Fig. 1). In line with the observed ADH activity, also the amount of acetaldehyde produced by the helicobacter strains was larger than that produced by the cytosols prepared
Acetaldehyde by Helicobacter pylori
Vol. 51, No. 17, 1992
1335
TABLE I
ETHANOL CONCENTRATION 12.5 mM
26mM
50mM
O.6M
1.OM
1.6M
2.6M
NCTC 11637
13±1
24±2
38±1
104±6
111 ± 6
116±8
111 ±7
NCTC 11638
18±2
33±3
56±3
128±10
119±9
111+10
81±6
HELICOSACTER STRAINS
OTHER BACTERIA
Escherichia coil
1,5±O.2
1,4±O.2
1,6±0.3
1.3±O.4
2.3+0.4
3.9±0.3
7.0±0.3
Carnpylobacter jejuni
O.2±O.1
0,5±0.3
1.2±0.2
4.1 ¢0.3
4.5±0.3
4.7+0,4
5.2±0.4
Klebsiella pneumoniae
166±27
169±22
190±23
220+36
280±48
290±72
252±86
In vitro ADH activities (mean +SE) expressed as nmol NADH/mg protein/min in two Helicobacterpyloristrains and in three other bacteria (Escherichia coil, Campylobacter jejuni, and Klebsiella pneumoniae). The results in each case are based on three to four separate cultures. ADH activity was determined with seven different ethanol concentrations.
from Escherichia coli or Campylobacterjejuni. By contrast, the amount of acetaldehyde found after incubation of cytosol prepared from Klebsiella pneumoniae with an ethanol containing solution was almost undetectable (Fig. 1).
=
4
Q.
w o
3-
E
2-
T T 0
NCTC 11637
NCTC 11638
I
t
E. coil
--
C. jejuni
K. pneumoniae
FIG. 1 A c e t a l d e h y d e production (mean + SE) expressed as pmol acetaldehyde p r o d u c e d / m g bacterial protein during an 18 h incubation by t w o Helicobacter pylori strains (NCTC 1 1 6 3 7 and NCTC 1 1 6 3 8 ) and by three other bacteria (Escherichia co~i, Campylobacter jejuni, and Klebsiella pneurnoniae). The results in each case are based on three separate cultures and acetaldehyde determinations.
1336
Acetaldehyde by Helicobacter pylori
Vol. 51, No. 17, 1992
Discussion Earlier studies have suggested that ammonia produced by Helicobacter pylori may play a pathogenetic role in Helicobacter pylori associated gastric injury (17). Our results show that Helicobacter pylori exhibits significant ADH activity which is associated with a high capacity to produce acetaldehyde in vitro. If this occurs also in vivo, bacterial acetaldehyde production may be a significant factor in the pathogenesis of Helicobacter pylori associated gastritis. Acetaldehyde, whether produced as an intermediate compound during bacterial fermentation of sugars to ethanol or as an oxidation product of endogenous or exogenous ethanol, could lead to the formation of acetaldehyde adducts with gastric mucus or mucosal proteins of the gastric epithelial cells in analogy to the adduct formation with hepatic proteins in the liver. This adduct formation and/or acetaldehyde mediated lipid peroxidation could be important risk factors for the development of gastric injury and cancer. Mean ADH activity observed in Helicobacter pylori at the ethanol concentrations likely to occur in the stomach after drinking of alcoholic beverages was more than 20 times higher than that we have found in histologically normal human gastric mucosal biopsy samples taken from the body of the stomach. In comparison to the other bacteria studied, cytosol from Klebsiella pneumoniae possessed even greater ADH activity. Despite this, acetaldehyde was virtually undetectable after incubation of cytosol from Klebsiella pneumoniae with an ethanol containing solution. This indicates that Klebsiella pneumoniae has an ability to rapidly convert acetaldehyde into some other compound. Acetate would be the most obvious choice if the bacteria contained also aldehyde dehydrogenase. Our preliminary experiments, however, did not detect any accumulation of acetate in the vials containing cytosol from Klebsiella pneumoniae. Thus, some other of the many pathways reported to be active in bacterial metabolism of ethanol and related compounds may be responsible for the rapid removal of acetaldehyde in Klebsiella pneumoniae. By virtue of possessing ADH activity, Helicobacter pylori could also contribute to the ethanol oxidation shown to occur in the stomach by gastric mucosal ADH activity (13,14). Differences in the infection status with Helicobacterpylori could, consequently, partly explain the interindividual differences observed in the magnitude of gastric ethanol oxidation. This possibility, however, needs to be established in future studies. Acknowledgements The skillful technical assistance of Ms. Eila Kelo and Ms. Leena-Riitta Korhonen is gratefully acknowledged. The work was supported by grants from the Yrj6 Jahnsson Foundation and Foundation of Gastric Diseases, Helsinki, Finland. References 1. 2. 3. 4. 5.
R.J. LAMED and J.G. ZEIKUS, Biochem J 19_.__55183-190(1981). J.C. BODE, S. RUST and C. BODE, Scand J Gastroentero119 853-856 (1984). H.A. KREBS and J.R. PERKINS, Biochem J 118635-644 (1970). E. BARAONA, R. JULKUNEN, L. TANNENBAUM and C.S. LIEBER, Gastroenterology 90103-110 (1986). M. SALASPURO and K. LINDROS, Alcohol-Related Diseases in Gastroenterology, H.K. Seitz and B. KommereU (eds), 106-123, Springer Verlag, Berlin, Heidelberg, New York, Tokyo (1985).
Vol. 51, No. 17, 1992
6. 7. 8. 9. 10. 11.
12. 13. 14. 15. 16. 17.
Acetaldehyde by Helicobacter pylori
1337
H.K. SEITZ, U.A. SIMANOWSKI, F.T. GARZON, J.M. RIDEOUT, T.J. PETERS, A. KOCH, M.R. BERGER, H. EINECKE and M. MAIWALD, Gastroenterology 98 406413 (1990). H. MIYAKAWA, E. BARAONA, J.C. CHANG, M.D. LESSER and C.S. LIEBER, Alcohol: Clin Exp Res 10 517-520 (1986). D.Y. GRAHAM, Gastroenterology 96 (Suppl) 615-625 (1989). T.U. KOSUNEN, J. HOOK, H. RAUTELIN and G. MYLLYLA, Scand J Gastroenterol 24 110-114 (1989). A. NOMURA, G.N. STEMMERMAN, P.-H. CHYOU, I. KATO, G.I. PEREZ-PEREZ and M.J. BLASER, N Engl J Meal 325 1132-1136 (1991). J. PARSONNET, G.D. FRIEDMAN, D.P. VANDERSTEEN, Y. CHANG, J.H. VOGELMAN, N. ORENTREICH and R.K. SIBLEY, N Engl J Med 325 1127-1131 (1991). P. SIPPONEN, T.U. KOSUNEN, J. VALLE, M. RIIHEL,~ and K. SEPP/~L,~, J Clin Pathol, in press. Y. LAMBOEUF, G. DE SAINT BLANQUAT and R. DERACHE, Biochem Pharmacol 39 542-545 (1981). R.J.K. JULKUNEN, L. TANNENBAUM, E. BARAONA and C.S. LIEBER, Alcohol 2 437-441 (1985). O.H. LOWRY, N.J. ROSEBROUGH, A.L. FARR and R.J. RANDALL, J Biol Chem 193 262-75 (1951). P. PIKKARAINEN, M. SALASPURO and C.S. LIEBER, Alcoholism: Clin Exp Res 3 259-261 (1979). A.T. TRIEBLING, M.A. KORSTEN, J.W. DLUGOSZ, F. PARONETTO and C.S. LIEBER, Dig Dis Sci 3_661089-1096 (1991).
