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Inhibition of gastric secretion in the rat with sodium oleate
INHIBITION
NORMAN LAWRENCE
D.
OF GASTRIC WITH SODIUM
ROCHMAN, PICKER,
M.D., B.A.,
PHILLIP AND
THE INHIBITORY EFFECT of large amounts of fats on gastric secretion has been known for almost a century [4]. Experiments have indicated that the effect may be due to fat in contact with the duodenal mucosa [3, 5, 91. Further experimentation using the products of lypolysis (fatty acids and soaps ) have been carried out with results indicating that these products have greater inhibitory effects on gastric mobility and secretion [7, 81. More recently [ 1, 21 intravenous emulsions of fat have been shown to decrease gastric secretions. Most of these previous experiments have used natural oils (mainly olive oil, and/ or the enzymic degradation products of these oils). Olive oil is composed of mixed glycerides of oleic acid 83.570, palmitive acid 9.4”/,, linoleic acid 4.0%, stearic acid 2.0%, and arachidic acid 0.9%). Minor constituents include squalcnc, phytosterol, and tocopherols [6]. It is the purpose of this experiment to eliminate some of the variables inherent in the use of impure natural products. In addition, we have attempted to elucidate, to some small extent, the possible pathway of this Ph enomenon. Toward this end, we have substituted, for the impure products, purified fatty acids in From the Surgical Research Laboratory, Department of Surgery, The Long Island Jewish Hospital, New Hyde Park, New York. Submitted for publication May 20, 1968.
SECRETION OLEATE
E.
CHARLOTTE
IN
LEAR,
THE
RAT
M.D.,
F.A.C.S.,
MANDELL,
M.S.
much smaller quantities as experimental inhibitors. In addition, we have used two different routes of administration, intravenous and intraperitoneal. Materials Oleic acid, linoleic acid, stearic acid, and propionic acid were used as 0.1 N solutions, adjusted to pH 8. Oleic acid (0.2 N), adjusted with NaOH, to pH 8 was used in one test group. Distilled water and normal saline were used in the controls. Male Wistar rats weighing between 100 and 200 gm. wcrc used as test animals. Method The volume of gastric secretions was determined in accordance with the method of Shay (10). The animals were purchased from a reputable supplv house and kept for 2 weeks in group cages to become accustomed to their environment. Solutions were administered intraperitoneally and intravenously after fasting the animals for 48 hours allowing HZ0 ad libitum. In those instances in which the test solutions were administered intraperitoneally, this was done through the abdominal wound made for the pvloric ligation just prior to its closure. In those instances in which the solutions were administered intravenously, a cutdown was made in the thigh, the femoral vein exposed and injected after closure of the ab213
JOURNAL
OF
SURGICAL
Table
1.
RESEARCH
VOL.
9
Results of Intraperitoneal
NO.
4,
1969
APRIL
Administration
Average ml. Number Secretion/ Substance of Rats 100 gm. Normal saline 24 3.6 Distilled water 31 3.1 Nothing 26 3.7 0.1 N Na propionate 22 3.3 0.1 N Na stearate 27 3.6 0.1 N Na linoleate 28 3.1 0.1 N Na oleatea 36 2.0 0.1 N Na oleatea 29 1.9 0.2 N Na oleatea 24 1.7 aThe differences between these three groups are not significant.
Table
2.
Results of Intravenous
Number of Rats Substance Normal saline 26 0.1 N Na oleatea 25 0.2 N Na oleat@ 25 aThe difference is not significant.
Administration
Average ml. Secretion/ 100 gm. 3.0 1.9 1.5
dominal wound. The animals were then sacrificed after a 4-hour period, again according to the method of Shay. Volumes were reported as cubic centimeters per centigram of weight. The results were then analyzed statistically and the criteria for significance was a P value of 0.01 or less when compared to a control treated with normal saline.
RESULTS Significant suppression of volume of gastric secretion by intraperitoneal administration of 0.1 N sodium oleate as compared to controls treated by intraperitoneal administration of normal saline occurred (Table 1). Intravenous administration of sodium oleate also significantly reduced the volume of gastric secretion as compared to the control of normal saline ( Table 2). Intraperitoneal sodium propionate, sodium linoleate, and sodium stearate had no 214
of 0.25 cc. of Test Substances
S.D. 0.833 0.971 0.922 0.851 0.726 0.934 0.770 0.987 0.943
S.E. 0.155 0.175 0.182 0.182 0.139 0.176 0.130 0.183 0.178
P > 0.050 > 0.050 > 0.200 > 0.500 > 0.500 < 0.001 < 0.001 -4 0.001
of 0.25 cc. of Test Substances
S.D. 0.845 0.698 0.914
S.E. 0.167 0.140 0.183
P < 0.001 < 0.001
effect, giving results not significantly from the controls.
DISCUSSION CONCLUSIONS
different
AND
It appears that oleic acid, as its sodium salt, decreases the volume of gastric secretion in rats by one-third over a 4-hour test period. It further appears that the effect is independent of the contact of this fatty acid with the duodenal mucosa, but rather is a function of its presence in the bloodstream. Others [4] have shown that olive oil in the duodenum without bile salts, does not inhibit gastric secretion. It is, therefore, reasonable to conclude that secretory inhibition by olive oil in the duodenum is caused by the product of lipolysis, Na oleate, after it has been absorbed and is in the bloodstream. The fact that neither linoleic acid ( Cl8 doubly unsaturated) stearic acid (Cls saturated), or propionic acid (C, saturated) suppressed gastric secretions
ROCHMAS
ET
AL.
indicates that this may be a specific pharmacological effect of oleic acid. The ability of linoleic acid ( Cl8 triply unsaturated) to affect secretion has not been evaluated. Current preliminary studies indicate a suppression of secretion of HCl with decreased concentration of HCl using slightly larger quantities of Na oleatc. SUMMARY The effect on gastric secretion in the rat by small quantities of sodium oleate (7.5 and 15.0 mg.) has been investigated. It was found that intravenous or intraperitoneal administration of small amounts (0.25 cc. of 0.1 N solutions) decreased gastric secretion by one-third over a 4-hour period. Sodium propionate, sodium stearate, sodium linoleate, other fatty acids, and normal saline did not inhibit gastric secretion under identical conditions. We conclude, therefore, that Na oleate may have a specific pharmacologic effect on gastric secretion in the rat. Furthermore, this action is not predicated upon contact with the duodenal mucosa but rather a function of its presence in the bloodstream.
SODIUM
OLEhTE
ISHIRITIOS
OF
GASTRIC
SECRETION
REFERENCES 1. Baume, P. E., Meng, H. C., and Law, D. H. Intravenous fat emulsion and gastric secretion in the rat. Amer. 1. Dig. Dis. ll:l, 1966. 2. Baume, P. E., Meng, H. C., and Law, D. H. Effects of intravenous lipids on rat gastric secretion. C&n. Res. 12:341, 1964. H. M., Nyhus, L. M. 3. Bibler, D. D., Harkins, Inhibitory effect of fat in the duodenum and upper small intestine on exogenous gastrin stimulated gastric secretion. Surgery 60:844, 1966. 4. Ewald, C. A., and Boas, J. Virchow Arch. Path. Anut. 104:271, 1866. 5. Long, J. F., and Brooks, F. P. Relation between inhibition of gastric secretion and absorption of fatty acids. Amer. Jour. Physiol. 209:447, 1965. 6. Merck Index, 7th ed. 1960. P. 754. 7. Quigley, J. P., and Meschan, I. Inhibition of the pyloric sphincter region by the digestion products of fats. Amer. I. Physiol. 134:803, 1941. 8. Menguy, R. Studies on the role of pancreatic and biliary secretions in the mechanisms of gastric inhibition by fat. Surgery 48:195, 1960. of gastric 9. Menguy, R. Mechanism of inhibition secretion by fat in the intestine. PTOC. Sot. Exp. Bid. Med. 102:274, 1959. 10. Shay, H., Sun, D. C. H., and Gruenstein, M. A quantitative method for measuring spontaneous gastric secretion in the rat. GastToenteroZogy 26: 906, 1954.
215
NORMAN LAWRENCE
D.
OF GASTRIC WITH SODIUM
ROCHMAN, PICKER,
M.D., B.A.,
PHILLIP AND
THE INHIBITORY EFFECT of large amounts of fats on gastric secretion has been known for almost a century [4]. Experiments have indicated that the effect may be due to fat in contact with the duodenal mucosa [3, 5, 91. Further experimentation using the products of lypolysis (fatty acids and soaps ) have been carried out with results indicating that these products have greater inhibitory effects on gastric mobility and secretion [7, 81. More recently [ 1, 21 intravenous emulsions of fat have been shown to decrease gastric secretions. Most of these previous experiments have used natural oils (mainly olive oil, and/ or the enzymic degradation products of these oils). Olive oil is composed of mixed glycerides of oleic acid 83.570, palmitive acid 9.4”/,, linoleic acid 4.0%, stearic acid 2.0%, and arachidic acid 0.9%). Minor constituents include squalcnc, phytosterol, and tocopherols [6]. It is the purpose of this experiment to eliminate some of the variables inherent in the use of impure natural products. In addition, we have attempted to elucidate, to some small extent, the possible pathway of this Ph enomenon. Toward this end, we have substituted, for the impure products, purified fatty acids in From the Surgical Research Laboratory, Department of Surgery, The Long Island Jewish Hospital, New Hyde Park, New York. Submitted for publication May 20, 1968.
SECRETION OLEATE
E.
CHARLOTTE
IN
LEAR,
THE
RAT
M.D.,
F.A.C.S.,
MANDELL,
M.S.
much smaller quantities as experimental inhibitors. In addition, we have used two different routes of administration, intravenous and intraperitoneal. Materials Oleic acid, linoleic acid, stearic acid, and propionic acid were used as 0.1 N solutions, adjusted to pH 8. Oleic acid (0.2 N), adjusted with NaOH, to pH 8 was used in one test group. Distilled water and normal saline were used in the controls. Male Wistar rats weighing between 100 and 200 gm. wcrc used as test animals. Method The volume of gastric secretions was determined in accordance with the method of Shay (10). The animals were purchased from a reputable supplv house and kept for 2 weeks in group cages to become accustomed to their environment. Solutions were administered intraperitoneally and intravenously after fasting the animals for 48 hours allowing HZ0 ad libitum. In those instances in which the test solutions were administered intraperitoneally, this was done through the abdominal wound made for the pvloric ligation just prior to its closure. In those instances in which the solutions were administered intravenously, a cutdown was made in the thigh, the femoral vein exposed and injected after closure of the ab213
JOURNAL
OF
SURGICAL
Table
1.
RESEARCH
VOL.
9
Results of Intraperitoneal
NO.
4,
1969
APRIL
Administration
Average ml. Number Secretion/ Substance of Rats 100 gm. Normal saline 24 3.6 Distilled water 31 3.1 Nothing 26 3.7 0.1 N Na propionate 22 3.3 0.1 N Na stearate 27 3.6 0.1 N Na linoleate 28 3.1 0.1 N Na oleatea 36 2.0 0.1 N Na oleatea 29 1.9 0.2 N Na oleatea 24 1.7 aThe differences between these three groups are not significant.
Table
2.
Results of Intravenous
Number of Rats Substance Normal saline 26 0.1 N Na oleatea 25 0.2 N Na oleat@ 25 aThe difference is not significant.
Administration
Average ml. Secretion/ 100 gm. 3.0 1.9 1.5
dominal wound. The animals were then sacrificed after a 4-hour period, again according to the method of Shay. Volumes were reported as cubic centimeters per centigram of weight. The results were then analyzed statistically and the criteria for significance was a P value of 0.01 or less when compared to a control treated with normal saline.
RESULTS Significant suppression of volume of gastric secretion by intraperitoneal administration of 0.1 N sodium oleate as compared to controls treated by intraperitoneal administration of normal saline occurred (Table 1). Intravenous administration of sodium oleate also significantly reduced the volume of gastric secretion as compared to the control of normal saline ( Table 2). Intraperitoneal sodium propionate, sodium linoleate, and sodium stearate had no 214
of 0.25 cc. of Test Substances
S.D. 0.833 0.971 0.922 0.851 0.726 0.934 0.770 0.987 0.943
S.E. 0.155 0.175 0.182 0.182 0.139 0.176 0.130 0.183 0.178
P > 0.050 > 0.050 > 0.200 > 0.500 > 0.500 < 0.001 < 0.001 -4 0.001
of 0.25 cc. of Test Substances
S.D. 0.845 0.698 0.914
S.E. 0.167 0.140 0.183
P < 0.001 < 0.001
effect, giving results not significantly from the controls.
DISCUSSION CONCLUSIONS
different
AND
It appears that oleic acid, as its sodium salt, decreases the volume of gastric secretion in rats by one-third over a 4-hour test period. It further appears that the effect is independent of the contact of this fatty acid with the duodenal mucosa, but rather is a function of its presence in the bloodstream. Others [4] have shown that olive oil in the duodenum without bile salts, does not inhibit gastric secretion. It is, therefore, reasonable to conclude that secretory inhibition by olive oil in the duodenum is caused by the product of lipolysis, Na oleate, after it has been absorbed and is in the bloodstream. The fact that neither linoleic acid ( Cl8 doubly unsaturated) stearic acid (Cls saturated), or propionic acid (C, saturated) suppressed gastric secretions
ROCHMAS
ET
AL.
indicates that this may be a specific pharmacological effect of oleic acid. The ability of linoleic acid ( Cl8 triply unsaturated) to affect secretion has not been evaluated. Current preliminary studies indicate a suppression of secretion of HCl with decreased concentration of HCl using slightly larger quantities of Na oleatc. SUMMARY The effect on gastric secretion in the rat by small quantities of sodium oleate (7.5 and 15.0 mg.) has been investigated. It was found that intravenous or intraperitoneal administration of small amounts (0.25 cc. of 0.1 N solutions) decreased gastric secretion by one-third over a 4-hour period. Sodium propionate, sodium stearate, sodium linoleate, other fatty acids, and normal saline did not inhibit gastric secretion under identical conditions. We conclude, therefore, that Na oleate may have a specific pharmacologic effect on gastric secretion in the rat. Furthermore, this action is not predicated upon contact with the duodenal mucosa but rather a function of its presence in the bloodstream.
SODIUM
OLEhTE
ISHIRITIOS
OF
GASTRIC
SECRETION
REFERENCES 1. Baume, P. E., Meng, H. C., and Law, D. H. Intravenous fat emulsion and gastric secretion in the rat. Amer. 1. Dig. Dis. ll:l, 1966. 2. Baume, P. E., Meng, H. C., and Law, D. H. Effects of intravenous lipids on rat gastric secretion. C&n. Res. 12:341, 1964. H. M., Nyhus, L. M. 3. Bibler, D. D., Harkins, Inhibitory effect of fat in the duodenum and upper small intestine on exogenous gastrin stimulated gastric secretion. Surgery 60:844, 1966. 4. Ewald, C. A., and Boas, J. Virchow Arch. Path. Anut. 104:271, 1866. 5. Long, J. F., and Brooks, F. P. Relation between inhibition of gastric secretion and absorption of fatty acids. Amer. Jour. Physiol. 209:447, 1965. 6. Merck Index, 7th ed. 1960. P. 754. 7. Quigley, J. P., and Meschan, I. Inhibition of the pyloric sphincter region by the digestion products of fats. Amer. I. Physiol. 134:803, 1941. 8. Menguy, R. Studies on the role of pancreatic and biliary secretions in the mechanisms of gastric inhibition by fat. Surgery 48:195, 1960. of gastric 9. Menguy, R. Mechanism of inhibition secretion by fat in the intestine. PTOC. Sot. Exp. Bid. Med. 102:274, 1959. 10. Shay, H., Sun, D. C. H., and Gruenstein, M. A quantitative method for measuring spontaneous gastric secretion in the rat. GastToenteroZogy 26: 906, 1954.
215