Acta Physiol Scand 1979, 106:257-265
Gastric acid secretion and drinking in the Atlantic cod (Gadusrnorhua) during acidic or hyperosmotic perfusion of the intestine BJORN HOLSTEIN Department of Zoophysiology, University of Goteborg, Sweden
HOLSTEIN, B.: Gastric acid secretion and drinking in the Atlantic cod (Gadus morhua) during acidic or hyperosmotic perfusion of the intestine. Acta Physiol Scand 1979, 106: 257-265. Received 18 Dec. 1978. ISSN 0001-6772. Department of Zoophysiology, University of Goteborg, Sweden. Cods were equipped with cannulae for drainage of the stomach and for separate perfusion of the stomach and intestine. Acidity, volume, and osmolality of the gastric outflow were measured. During perfusion of the intestine with a near-isosmotic saline ( I part sea-water,2 parts distilled water, '33% SW) and the stomach with pure ('100%) SW,gastric acid output was high and volume output slightly above the infused volume. The osmolality of the gastric perfusate decreased during passage of the stomach. It was concluded that no drinking occurred, and that the decreased osmolality was due to dilution by gastric secretions and osmotically lost water. When substituting the isosmotic intestinal perfusion to a dehydrating perfusion (100% SW), gastric acid secretion was depressed but volume output was unaffected. Also perfusion of the intestine with acidified 33 % SW depressed gastric acid secretion and in addition increased volume and osmolality of the gastric outflow. The results suggest that perfusion of the intestine depresses the drinking reflex and that this depression is surmounted by intestinal acidification. Possible mediators of the intestinal feed-back mechanism for the inhibition of gastric acid secretion are discussed. Key words: Drinking, fish physiology, gastric acid secretion. intestinal acidification
In the regulation of gastric acid secretion, the cephalic, the gastric and the intestinal phases are recognized (Grossman 1967, Wright & Hirsckowitz 1976, Cooperman 1977). The intestinal phase comprises both stimulatory and inhibitory components (Christiansen 1978) and has been the subject of many mammalian studies. Studies of gastric acid secretion in submammalian species, excepting the isolated gastric mucosa from the frog, are infrequent, and concerning the intestinal phase, the field seems completely ignored. The continuous drinking of the sea-water teleost was utilized to wash gastric secretions out of the cannulated codfish stomach. This technique, previously used in secretory studies in this laboratory (Holstein 1975, 1976,1977) suffered from the serious disadvantage to dehydrate the fish. To divert gastric secretions from the intestine, the pylorus was ligated and this prevented intestinal resorption of water and thus rendered replacement of water lost 17-795877
to the hyperosmotic environment impossible. To permit this compensation, the intestine was cannulated and perfused. Perfusion of the intestine at a rate of about 8 ml/h completely inhibited drinking, perfusion at a lower rate decreased drinking (Holstein 1979). These effects, however, were independent of the degree of dilution of the sea-water used for the perfusion; both dehydrating solutions (100% SW. 67% SW') and solutions permitting the fish to maintain its water balance (50% SW, 33% SW') inhibited drinking. To be able to collect gastric secretions in the absence of drinking, also the stomach was cannulated and perfused. It was found that gastric acid secretion in 100% SW- or 67% SW-intestinally perfused fishes was low or absent and that 50% SW- and 33 % SW-perfused animals exhibited I
100% SW indicates pure sea-water. 67%. 50%. and
33% SW indicates mixtures of 100% SW and distilled water in the proportions 2+ I , 1 + I , and 1 +2, respectively. Arrti Plrr.siol . k i n d 106
258
B j i h Holsteiii PERFUSION OF INTESTINE 4
33% sw
12c
a
E IOC
I
d F
a
u ea
b t-
Y
6C
t
ga 4c c
2
EJ
CONTROL PERIOD (I00%) D
2c
C
55.8 I4.2vmol H'lkgxh 75.1 : 15.5
- -
GASTRIC PERFU! 8.2 8.4 ml/h
-
N RATE;
1 HOURS
Fig. 1 . Effect of intestinal acidification on gastric acid secretion (upper panel) and
gastric volume output (lower panel). The group receiving the lower acid load comprised 8 animals, the group receiving the higher load 5 animals. Gastric perfusion with 100% SW-PR. *, **, ***, denotes a significant difference from the 'control h at the P
Gastric acid secretion and drinking in the Atlantic cod (Gadusrnorhua) during acidic or hyperosmotic perfusion of the intestine BJORN HOLSTEIN Department of Zoophysiology, University of Goteborg, Sweden
HOLSTEIN, B.: Gastric acid secretion and drinking in the Atlantic cod (Gadus morhua) during acidic or hyperosmotic perfusion of the intestine. Acta Physiol Scand 1979, 106: 257-265. Received 18 Dec. 1978. ISSN 0001-6772. Department of Zoophysiology, University of Goteborg, Sweden. Cods were equipped with cannulae for drainage of the stomach and for separate perfusion of the stomach and intestine. Acidity, volume, and osmolality of the gastric outflow were measured. During perfusion of the intestine with a near-isosmotic saline ( I part sea-water,2 parts distilled water, '33% SW) and the stomach with pure ('100%) SW,gastric acid output was high and volume output slightly above the infused volume. The osmolality of the gastric perfusate decreased during passage of the stomach. It was concluded that no drinking occurred, and that the decreased osmolality was due to dilution by gastric secretions and osmotically lost water. When substituting the isosmotic intestinal perfusion to a dehydrating perfusion (100% SW), gastric acid secretion was depressed but volume output was unaffected. Also perfusion of the intestine with acidified 33 % SW depressed gastric acid secretion and in addition increased volume and osmolality of the gastric outflow. The results suggest that perfusion of the intestine depresses the drinking reflex and that this depression is surmounted by intestinal acidification. Possible mediators of the intestinal feed-back mechanism for the inhibition of gastric acid secretion are discussed. Key words: Drinking, fish physiology, gastric acid secretion. intestinal acidification
In the regulation of gastric acid secretion, the cephalic, the gastric and the intestinal phases are recognized (Grossman 1967, Wright & Hirsckowitz 1976, Cooperman 1977). The intestinal phase comprises both stimulatory and inhibitory components (Christiansen 1978) and has been the subject of many mammalian studies. Studies of gastric acid secretion in submammalian species, excepting the isolated gastric mucosa from the frog, are infrequent, and concerning the intestinal phase, the field seems completely ignored. The continuous drinking of the sea-water teleost was utilized to wash gastric secretions out of the cannulated codfish stomach. This technique, previously used in secretory studies in this laboratory (Holstein 1975, 1976,1977) suffered from the serious disadvantage to dehydrate the fish. To divert gastric secretions from the intestine, the pylorus was ligated and this prevented intestinal resorption of water and thus rendered replacement of water lost 17-795877
to the hyperosmotic environment impossible. To permit this compensation, the intestine was cannulated and perfused. Perfusion of the intestine at a rate of about 8 ml/h completely inhibited drinking, perfusion at a lower rate decreased drinking (Holstein 1979). These effects, however, were independent of the degree of dilution of the sea-water used for the perfusion; both dehydrating solutions (100% SW. 67% SW') and solutions permitting the fish to maintain its water balance (50% SW, 33% SW') inhibited drinking. To be able to collect gastric secretions in the absence of drinking, also the stomach was cannulated and perfused. It was found that gastric acid secretion in 100% SW- or 67% SW-intestinally perfused fishes was low or absent and that 50% SW- and 33 % SW-perfused animals exhibited I
100% SW indicates pure sea-water. 67%. 50%. and
33% SW indicates mixtures of 100% SW and distilled water in the proportions 2+ I , 1 + I , and 1 +2, respectively. Arrti Plrr.siol . k i n d 106
258
B j i h Holsteiii PERFUSION OF INTESTINE 4
33% sw
12c
a
E IOC
I
d F
a
u ea
b t-
Y
6C
t
ga 4c c
2
EJ
CONTROL PERIOD (I00%) D
2c
C
55.8 I4.2vmol H'lkgxh 75.1 : 15.5
- -
GASTRIC PERFU! 8.2 8.4 ml/h
-
N RATE;
1 HOURS
Fig. 1 . Effect of intestinal acidification on gastric acid secretion (upper panel) and
gastric volume output (lower panel). The group receiving the lower acid load comprised 8 animals, the group receiving the higher load 5 animals. Gastric perfusion with 100% SW-PR. *, **, ***, denotes a significant difference from the 'control h at the P
