Digestion 14: 332-341 (1976)
Effect of Duodenal Acidification on Gastric Mucus and Acid Secretion in Conscious Cats M. Vague and G. Perret Unité de Physiopathologie Digestive, Institut national de la Santé et de la Recherche médicale, Lyon
Key Words. Cats • Cholecystokinin • Fucose • Gastric juice • Gastrin • Glycoproteins • Histamine • Mucus • Pepsin • Polysaccharides • Uronic acids Abstract. In cats with gastric fistulae and Heidenhain pouches, the effect of acid entering the duodenum on secretion of acid, pepsin, and mucus from the Heidenhain pouch during maximal acid stimulation with pentagastrin or histamine, was studied. Duodenal acidification produced stimulation of pepsin and mucus secretion comparable to that in duced by exogenous hormones (secretin and the combination of secretin with cholecysto kinin). In addition, duodenal acidification caused an increase in acid secretion, thus sug gesting that, in addition to secretin and cholecystokinin, a factor that stimulates acid secre tion was also released by acid.
We have shown previously that exogenous hormones, secretin (19), chole cystokinin (CCK) (17), pentagastrin (18), induce an increase o f mucus in the gastric juice in unanesthetized cats with a Heidenhain pouch (HP) and a gastric fistula (GF). In order to evaluate the physiological effects o f the gastrointestinal hormones, we determined the action on mucus secretion o f endogenously re leased duodenal hormones by opening or closing the gastric fistula during maximal gastric acid secretion induced by histamine or pentagastrin. Acid entering the duodenum releases mostly secretin but also CCK (1). As previously, the two kinds o f molecules constituting gastric mucus, polysaccharide and glyco protein, were evaluated by measuring uronic acid and fucose concentrations o f the gastric juice, as well as acid and pepsin secretions.
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Received: April 22, 1975: accepted: March 17. 1976.
Vagne/Parrel
333
Methods Three cals, one male and two females, weighing 2-3 kg. were operated under pento barbital anesthesia and a HP was made opening to the outside by a Gregory cannula (10). In a second stage, at least 3 weeks later, a plastic cannula (8) was placed in the remaining part of the stomach. After a I-month recovery period, the experiments were performed twice a week. The animals were fasted 18 h before each test with free access to water. Basal secretion was collected for two periods of 15 min during a continuous intra venous infusion of 0.15 M NaCI given with a peristaltic pump (Harvard App. Co., Millis. Mass.) at a rate of 13 ml/h. (1) Pentagastrin stimulated secretion was induced by addition to the saline infusion of pentagastrin (101, Macclesfield. Ches.) at a dose of 32 /¿g-kg"1-h~1 for ten 15-min periods. (2) Histamine-stimulated secretion was induced by addition to the saline of histamine diHCI at a dose of 0.32 mg-kg"1- h '1 for ten 15-min periods. In three experiments for each stimulant, in each of the cats, the GF remained open and gastric secretion from both GF and HP was collected. In three experiments, the GF was closed after 1 h of stimulation. The experiments were performed in a randomized order for each stimulant. Chemical Determinations Ih e gastric juice was measured and homogenized with an ultrasonic disintegrator (Measuring and Scientific Equipment. London). Acid concentration was determined on 0.2 ml of gastric juice with an autoburet and pH meter (Radiometer, Copenhagen. Den mark) using 0.2 N NaOH and titrating to pH 7. Pepsin concentration was measured with a 15 min proteolysis of albumin by a micromodification of our technique (16). The samples had been kept frozen for about 2 months. Uronic acid concentration was determined by the technique of Bitter and Muir (3), slightly modified by us as previously described (18). Fucose concentration was measured by the technique described by Dische and Shettles (7) as reported (18). The output of each constituent was calculated per 15 min. Statistical significance of the difference was estimated by the t test for either paired or unpaired values as appropriate. The comparison between open and closed GF was done in all cases during period 7 10. I he ratios between the different constituents were compared by analysis of variance.
Histamine and pentagastrin produced an increase of the volumes of both GF and HP. The mean peak volume was obtained 60 and 30 min after the beginning of the infusion, respectively, for histamine and pentagastrin, and then the volumes decreased slowly. Closing the GF increased the volume secreted by HP during histamine and pentagastrin (p < 0.01) (fig. 1). In a preliminary experiment, the volume o f gastric juice remaining in the main stomach was measured at the end of 2 V2 h o f GF closing. As it was lower than the volume secreted in a 15-min period for each cat, the gastric emptying has been considered as satisfactory in these animals. Acid output was strongly stimulated by histamine and pentagastrin (fig. 2). Closing the GF increased the acid output during histamine (p < 0.01) and acid
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Results
Vagne/Perrel
334
15-mm periods
Fig. I. Volumes secreted by the HP during histamine (top) and pentagastrin (bottom) with GF open (------- ) and G I- closed (-------- ). For this and subsequent figures each point is the mean of three experiments in each of the three cats. The vertical bars are SEM.
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concentration and output during pentagastrin stimulation (p < 0.001). The in crease was 8 9 1 -1 ,0 9 0 ¿(Eq/h for histamine (22%) and 8 5 8 -1 ,0 7 4 for penta gastrin (25 %). During pentagastrin stimulation, the acid output in the main stomach (GF) was l,200)uEq/15 min ± 144 in period 4 (just before closing the GF) and 1,196 ± 91 /aEq/15 min in the same period in the series where the GF was not closed. The acid output o f the main stomach was 957 ± 65 juEq/15 min in this latter (mean o f period 7 -1 0 ). During histamine stimulation, the acid output from the GF before closing it was 930 ± 94^tEq/15 min (period 4) and in the other series 860 ± 80juEq/15 min (period 4) and 910 yuEq/15 min (mean o f period 7—10). Pepsin output was stimulated by pentagastrin (fig. 3). Closing the gastric fistula increased both concentration and output of pepsin (p < 0.001). During histamine stimulation, pepsin output decreased to a very low level and closing the GF also induced a stimulation (p < 0.02).
Gastrointestinal Hormones and Mucus Secretion in the Cat
335
Fig. 2. Acid output from the HP during histamine (top) and pentagastrin (bottom) with GF open (--------) and GF closed (-------- ).
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Fig. 3. Pepsin output from HP during pentagastrin with GF open (--------) and GF closed (--------).
336
Vagne/Perrel
t5-mm periods
Uronic acid concentration decreased during both stimulations. Closing the GF induced a sustained increase in the concentrations (p < 0.001). Uronic acid output was stimulated by histamine and pentagastrin (fig. 4). As with the pepsin response, the uronic acid response to histamine was lower than to pentagastrin and closing the GF increased the uronic acid output in HP secretion during histamine and pentagastrin stimulation (p < 0.001). With the GF open, the ratio uronic acid/pepsin increased from the first period o f pentagastrin (1st to 4th 15-min period) to the second (5th to 10th 15-min period). On the contrary, the ratios decreased when the GF was closed (table I). A statistically significant correlation was always obtained between uronic acid and pepsin (table II). Fucose concentration decreased with both stimulations. Closing the GF did not statistically change the concentrations. Fucose output increased during histamine and pentagastrin stimulation (fig. 5). Closing the GF induced an in creased output (p < 0.03 with histamine, p < 0.01 with pentagastrin). The ratios fucose/uronic acid decreased from basal to stimulation periods with either penta gastrin or histamine (table I). Closing the GF induced a decrease of the ratios.
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Fig. 4. Uronic acid output (URO) from HP during histamine (top) and pentagastrin (bottom) with GF open (--------) and GF closed (--------).
Gastrointestinal Hormones and Mucus Secretion in the Cat
337
t5-mm periods
Fig. 5. Fucose output from HP during histamine (top) and pentagastrin (bottom) with GF open (------- ) and GF closed (-------- ).
This shows that pentagastrin and histamine stimulated uronic acid more strongly than fucose as do endogenous hormones. But in every case, there was a correla tion between these two components (table II) (nonsignificant in basal because o f the small number of data).
These experiments show that in the cat, histamine stimulated gastric mucus secretion as well as acid secretion. Both components o f gastric mucus, poly saccharides (evaluated by the variation o f uronic acids) and glycoproteins (evalu ated by the variation o f fucose) were stimulated by histamine as well as by pentagastrin, this finding confirms our previous results (18). The shape o f the response as a function of time represented by a peak followed by a steadily decreasing plateau, suggests a washing out o f the gastric mucus layer by the parietal secretion. However, in both stimulations, the responses after 2'l2 h were
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/8/2018 11:11:38 AM
Discussion
338
Vagne/Perret
Table I. Ratios between concentrations of the different components, fucose (F), uronic acid (U), pepsin (P) in the gastric juice from HP in three cats (mean, SEM and number of samples of gastric juice); the ratios already determined in an other series of experi ments for pentagastrin are not repeated (17) Saline or pentagastrin 32 Mg'kg'1- h '1
Saline or histamine 0.32 mg-kg’ 1- h '1
F/U
F/P
U/P
F/U
2.30 0.30 18
0.58 0.20 11
0.37 0.14 11
3.25 0.84 5
Period 1 4 Mean SEM n
0.93 0.05 72
0.36 0.06 59
0.34 0.05 58
1.77 0.14 54
Period 5 10. GF open Mean SEM n
0.98 0.05 54
0.55
0.65
42
1.25 0.06 54
Period 5 10, GF closed Mean SEM n
0.75 0.04 54
0.10 0.01 36
Basal
Analysis of variance p
Effect of Duodenal Acidification on Gastric Mucus and Acid Secretion in Conscious Cats M. Vague and G. Perret Unité de Physiopathologie Digestive, Institut national de la Santé et de la Recherche médicale, Lyon
Key Words. Cats • Cholecystokinin • Fucose • Gastric juice • Gastrin • Glycoproteins • Histamine • Mucus • Pepsin • Polysaccharides • Uronic acids Abstract. In cats with gastric fistulae and Heidenhain pouches, the effect of acid entering the duodenum on secretion of acid, pepsin, and mucus from the Heidenhain pouch during maximal acid stimulation with pentagastrin or histamine, was studied. Duodenal acidification produced stimulation of pepsin and mucus secretion comparable to that in duced by exogenous hormones (secretin and the combination of secretin with cholecysto kinin). In addition, duodenal acidification caused an increase in acid secretion, thus sug gesting that, in addition to secretin and cholecystokinin, a factor that stimulates acid secre tion was also released by acid.
We have shown previously that exogenous hormones, secretin (19), chole cystokinin (CCK) (17), pentagastrin (18), induce an increase o f mucus in the gastric juice in unanesthetized cats with a Heidenhain pouch (HP) and a gastric fistula (GF). In order to evaluate the physiological effects o f the gastrointestinal hormones, we determined the action on mucus secretion o f endogenously re leased duodenal hormones by opening or closing the gastric fistula during maximal gastric acid secretion induced by histamine or pentagastrin. Acid entering the duodenum releases mostly secretin but also CCK (1). As previously, the two kinds o f molecules constituting gastric mucus, polysaccharide and glyco protein, were evaluated by measuring uronic acid and fucose concentrations o f the gastric juice, as well as acid and pepsin secretions.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/8/2018 11:11:38 AM
Received: April 22, 1975: accepted: March 17. 1976.
Vagne/Parrel
333
Methods Three cals, one male and two females, weighing 2-3 kg. were operated under pento barbital anesthesia and a HP was made opening to the outside by a Gregory cannula (10). In a second stage, at least 3 weeks later, a plastic cannula (8) was placed in the remaining part of the stomach. After a I-month recovery period, the experiments were performed twice a week. The animals were fasted 18 h before each test with free access to water. Basal secretion was collected for two periods of 15 min during a continuous intra venous infusion of 0.15 M NaCI given with a peristaltic pump (Harvard App. Co., Millis. Mass.) at a rate of 13 ml/h. (1) Pentagastrin stimulated secretion was induced by addition to the saline infusion of pentagastrin (101, Macclesfield. Ches.) at a dose of 32 /¿g-kg"1-h~1 for ten 15-min periods. (2) Histamine-stimulated secretion was induced by addition to the saline of histamine diHCI at a dose of 0.32 mg-kg"1- h '1 for ten 15-min periods. In three experiments for each stimulant, in each of the cats, the GF remained open and gastric secretion from both GF and HP was collected. In three experiments, the GF was closed after 1 h of stimulation. The experiments were performed in a randomized order for each stimulant. Chemical Determinations Ih e gastric juice was measured and homogenized with an ultrasonic disintegrator (Measuring and Scientific Equipment. London). Acid concentration was determined on 0.2 ml of gastric juice with an autoburet and pH meter (Radiometer, Copenhagen. Den mark) using 0.2 N NaOH and titrating to pH 7. Pepsin concentration was measured with a 15 min proteolysis of albumin by a micromodification of our technique (16). The samples had been kept frozen for about 2 months. Uronic acid concentration was determined by the technique of Bitter and Muir (3), slightly modified by us as previously described (18). Fucose concentration was measured by the technique described by Dische and Shettles (7) as reported (18). The output of each constituent was calculated per 15 min. Statistical significance of the difference was estimated by the t test for either paired or unpaired values as appropriate. The comparison between open and closed GF was done in all cases during period 7 10. I he ratios between the different constituents were compared by analysis of variance.
Histamine and pentagastrin produced an increase of the volumes of both GF and HP. The mean peak volume was obtained 60 and 30 min after the beginning of the infusion, respectively, for histamine and pentagastrin, and then the volumes decreased slowly. Closing the GF increased the volume secreted by HP during histamine and pentagastrin (p < 0.01) (fig. 1). In a preliminary experiment, the volume o f gastric juice remaining in the main stomach was measured at the end of 2 V2 h o f GF closing. As it was lower than the volume secreted in a 15-min period for each cat, the gastric emptying has been considered as satisfactory in these animals. Acid output was strongly stimulated by histamine and pentagastrin (fig. 2). Closing the GF increased the acid output during histamine (p < 0.01) and acid
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/8/2018 11:11:38 AM
Results
Vagne/Perrel
334
15-mm periods
Fig. I. Volumes secreted by the HP during histamine (top) and pentagastrin (bottom) with GF open (------- ) and G I- closed (-------- ). For this and subsequent figures each point is the mean of three experiments in each of the three cats. The vertical bars are SEM.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/8/2018 11:11:38 AM
concentration and output during pentagastrin stimulation (p < 0.001). The in crease was 8 9 1 -1 ,0 9 0 ¿(Eq/h for histamine (22%) and 8 5 8 -1 ,0 7 4 for penta gastrin (25 %). During pentagastrin stimulation, the acid output in the main stomach (GF) was l,200)uEq/15 min ± 144 in period 4 (just before closing the GF) and 1,196 ± 91 /aEq/15 min in the same period in the series where the GF was not closed. The acid output o f the main stomach was 957 ± 65 juEq/15 min in this latter (mean o f period 7 -1 0 ). During histamine stimulation, the acid output from the GF before closing it was 930 ± 94^tEq/15 min (period 4) and in the other series 860 ± 80juEq/15 min (period 4) and 910 yuEq/15 min (mean o f period 7—10). Pepsin output was stimulated by pentagastrin (fig. 3). Closing the gastric fistula increased both concentration and output of pepsin (p < 0.001). During histamine stimulation, pepsin output decreased to a very low level and closing the GF also induced a stimulation (p < 0.02).
Gastrointestinal Hormones and Mucus Secretion in the Cat
335
Fig. 2. Acid output from the HP during histamine (top) and pentagastrin (bottom) with GF open (--------) and GF closed (-------- ).
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Fig. 3. Pepsin output from HP during pentagastrin with GF open (--------) and GF closed (--------).
336
Vagne/Perrel
t5-mm periods
Uronic acid concentration decreased during both stimulations. Closing the GF induced a sustained increase in the concentrations (p < 0.001). Uronic acid output was stimulated by histamine and pentagastrin (fig. 4). As with the pepsin response, the uronic acid response to histamine was lower than to pentagastrin and closing the GF increased the uronic acid output in HP secretion during histamine and pentagastrin stimulation (p < 0.001). With the GF open, the ratio uronic acid/pepsin increased from the first period o f pentagastrin (1st to 4th 15-min period) to the second (5th to 10th 15-min period). On the contrary, the ratios decreased when the GF was closed (table I). A statistically significant correlation was always obtained between uronic acid and pepsin (table II). Fucose concentration decreased with both stimulations. Closing the GF did not statistically change the concentrations. Fucose output increased during histamine and pentagastrin stimulation (fig. 5). Closing the GF induced an in creased output (p < 0.03 with histamine, p < 0.01 with pentagastrin). The ratios fucose/uronic acid decreased from basal to stimulation periods with either penta gastrin or histamine (table I). Closing the GF induced a decrease of the ratios.
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Fig. 4. Uronic acid output (URO) from HP during histamine (top) and pentagastrin (bottom) with GF open (--------) and GF closed (--------).
Gastrointestinal Hormones and Mucus Secretion in the Cat
337
t5-mm periods
Fig. 5. Fucose output from HP during histamine (top) and pentagastrin (bottom) with GF open (------- ) and GF closed (-------- ).
This shows that pentagastrin and histamine stimulated uronic acid more strongly than fucose as do endogenous hormones. But in every case, there was a correla tion between these two components (table II) (nonsignificant in basal because o f the small number of data).
These experiments show that in the cat, histamine stimulated gastric mucus secretion as well as acid secretion. Both components o f gastric mucus, poly saccharides (evaluated by the variation o f uronic acids) and glycoproteins (evalu ated by the variation o f fucose) were stimulated by histamine as well as by pentagastrin, this finding confirms our previous results (18). The shape o f the response as a function of time represented by a peak followed by a steadily decreasing plateau, suggests a washing out o f the gastric mucus layer by the parietal secretion. However, in both stimulations, the responses after 2'l2 h were
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/8/2018 11:11:38 AM
Discussion
338
Vagne/Perret
Table I. Ratios between concentrations of the different components, fucose (F), uronic acid (U), pepsin (P) in the gastric juice from HP in three cats (mean, SEM and number of samples of gastric juice); the ratios already determined in an other series of experi ments for pentagastrin are not repeated (17) Saline or pentagastrin 32 Mg'kg'1- h '1
Saline or histamine 0.32 mg-kg’ 1- h '1
F/U
F/P
U/P
F/U
2.30 0.30 18
0.58 0.20 11
0.37 0.14 11
3.25 0.84 5
Period 1 4 Mean SEM n
0.93 0.05 72
0.36 0.06 59
0.34 0.05 58
1.77 0.14 54
Period 5 10. GF open Mean SEM n
0.98 0.05 54
0.55
0.65
42
1.25 0.06 54
Period 5 10, GF closed Mean SEM n
0.75 0.04 54
0.10 0.01 36
Basal
Analysis of variance p
