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Effect of pepsin on ionic permeability of canine esophageal mucosa
JOURNAL
Effect
OF SURGICAL
RESEARCH
of Pepsin
22, 5-8
on Ionic
(1977)
Permeability
of Canine
STROOS SAFAIE-SHIRAZI, Department
of Surgery,
The University
of IOWU
Submitted
for publication
Recently we have demonstrated that a barrier to H+ is present in the esophagus of the dog and man and that in the presence of bile salts this barrier is destroyed with a resultant increased loss of H+ from the esophageal lumen [9- I 11. We postulated that the high frequency of esophagitis and ulceration associated with intraesophageal bile and HCl reported in the literature [3, 51 may be due to increased permeability of the esophageal mucosa to H+ induced by bile salts. Because bile and hydrochloric acid are not the only agents present in gastric juice and because esophagitis also has been produced in animals by pepsin and HCl [2], the present study was designed to assess the effect of pepsin on the permeability of esophageal mucosa and to clarify the pathogenesis of peptic esophagitis produced by pepsin and acid. MATERIALS
AND METHODS
5 0 1977 by Academic Press, Inc. of reproduction in any form reserved.
April
Mucosa
M.D. of Medicine,
Iowa
City,
Iowu
52242
13, 1976
of 50 ml was chosen as the quantity of test solution to be used in these experiments. Test solutions contained 25, 50, or 100 mequiv per liter of HCl and 2 g per liter of polyethylene glycol (PEG) as an inert nonabsorbable dilution indicator. Pure pepsin crystals (7500 or 15,000 units) were added to each 50 ml of test solution. The rinse solution was indicator-free normal saline (NaCl). Part A (HCI alone, 14 dogs). A solution of 25, 50, or 100 mequiv/liter of HCl + 2 mg/ml of polyethylene glycol (PEG) was instilled into the esophagus. This was thoroughly mixed for 1 min by gentle injection and aspiration. A 2-ml aliquot was removed, and the remainder of the solution was left in the esophagus for 30 min. The esophageal contents were then completely aspirated, the volume was measured, and a 5-ml aliquot was saved for analysis. The esophagus was thoroughly rinsed with 100 ml of NaCl after each study; for each concentration of HCl the experiment was repeated twice. Two dogs were killed and the esophagi were examined microscopically. Part B (HCl + pepsin, 12 dogs). After 2 weeks, the 12 remaining animals were prepared for studies, as previously outlined. In four dogs 50 ml of test solution containing 25 mequiv/liter of HCl + 2 mg/ml PEG + 7500 units of pepsin was instilled into the esophagus for two periods of 30 min each. The experiment was repeated with the sameconcentration of HCl but a higher concentration of pepsin (15,000 units) for another two periods of 30 min. The same procedure was then repeated with 50 mequivl liter of HCl and two concentrations of pepsin (7500 and 15,000 units) in another
Healthy, adult mongrel dogs were anesthetized with pentobarbital, 30 mg/kg body weight. A double-lumen oro-esophageal tube was placed in the esophagus. A celiotomy was performed, the gastroesophageal junction was identified and occluded with a noncrushing vascular clamp. The esophageal tube was then positioned just proximal to the clamp. Through a high cervical incision, the esophagus was ligated with an umbilical tape just distal to the thyroid cartilage. By repeated measurements of esophageal capacity, we found that the instillation of 100 ml of saline regularly increased intraesophageal pressure by only 3 to 5 cm of saline. Therefore, a volume Copyright All rights
College
Esophageal
6
JOURNAL
OF SURGICAL
RESEARCH: TABLE
IONIC
VOL. 22, NO. I, JANUARY
1977
1
MOVEMENT IN RESPONSE TO INSTILLATION OF 25, 50, OR 100 mmol/liter CONCENTRATIONS OF PEPSIN INTO PROXIMALLY AND DISTALLY OCCLUDED
HC1 PLUS Two CANINE
DIFFERENT ESOPHAGUS
Milliliters of H,O Solution instilled HCI alone 25 mequiv -0.12 50 mequiv -0.17 100 mequiv -0.49 HCI + pepsin 25 mequiv HCl + 7500 U pepsin -0.30 25 mequiv HCI + 15,OOOUpepsin -0.23 50 mequiv HCI + 7500 U pepsin -0.92 50 mequiv HCI + 15,OOOUpepsin -0.65 100 mequiv HCI + 7500 U pepsin -2.15 100 mequiv HCl + 15,000 U pepsin -1.40
H
Cl
Na
K
flLlX
2 0.02 k 0.16 f 0.16
-0.28 -c 0.22 +0.40 2 0.16 -0.39 ” 0.25 +0.42 2 0.13 -0.31 + 0.12 +0.31 + 0.26
+0.09 2 0.07 +0.09 t 0.11 +0.16 2 0.07
2.54 3.74 1.51
2 0.07
-0.56 f 0.15 +0.75 2 0.19 +0.018 2 0.004 +0.18 2 0.07
2.11
2 0.11
-2.37 k 0.43 +2.73 f 0.41
+0.08 f 0.009
+0.22 f 0.13
3.12
t 0.09”
-0.87 + 0.08 +1.61 2 0.11
+0.04 k 0.002
+0.26 2 0.09
3.14
k 0.04”
-1.44 k 0.08 +2.22 2 0.08
+0.08 rt 0.003
+0.15 k 0.15
4.64
2 0.17”
-0.33 f 0.07 +1.55 -c 0.11
+0.04 f 0.005
+0.41 2 0.25
2.59
+0.07 f 0.006 +0.31 k 0.12
3.72
k 0.14* -0.11 2 0.08 +I.62 -e 0.09
+O.Ol +O.Ol +O.Ol
PC%
n P < 0.002. *P < 0.01. ‘P < 0.001.
four dogs and again with 100 mequiv/liver of HCI and the same concentrations of pepsin (7500 and 15,000 units) in the last remaining dogs. Between each period of experimentation the esophagus was washed with 100 ml of rinse solution (NaCl). Animals were killed, the esophagi were examined, and appropriate sections were obtained for histologic examination. Laboratory measurements and calculations. After centrifugation to obtain clear
supernatant solutions, H+, Cl-, Na+, K+, and PEG concentrations were determined in all aliquots. PEG was measured by a turbidimetric method, and H+ content was determined by titration with 0.1 N NaOH to pH 7.4 with the use of a glass electrode. Sodium and potassium concentrations were determined with a flame photometer (IL Model No. 143, Instrumental Laboratory,
Inc., Lexington, Massachusetts). Chloride concentrations were determined by a chloridometer (Buchler-Collove; Buchler Instrument Division, Nuclear Chicago Corp., Fort Lee, New Jersey). p CO, was measured with an automatic blood gas and pH meter (Model No. 3 13, Instrumental Laboratory) immediately after obtaining the aliquots. The residual volume in the esophagus and the volume secreted, if any, during each 30min period were calculated from dilution of the nonabsorbable PEG marker. The total mass of H+, Na+, K+, and Cl- present initially after mixing and at the end of the 30-min test periods was calculated by multiplying the concentration of these ions by the volume. The net flux in and out of the lumen was determined by subtracting the initial mass from the final mass. A positive
SAFAIE-SHIRAZI:
PEPSIN
AND
flux (+) indicated a net addition of ions to the lumen, and a negative flux (-) indicated a net loss of ions from the lumen. A Student’s t test was used to analyze paired observations.
ESOPHAGEAL
MUCOSA
7
esophagus showed complete epithelial erosion with proteinaceous edema and proteolytic changes involving the entire thickness of the lamina propria. DISCUSSION
RESULTS
The mean net flux of ions for each 30-min period of experimentation is shown in Table 1. In Part A (HCl alone), the mean loss of H+ was -0.12 ? 0.02 mequiv/30 min when the concentration of H+ was 25 mequiv/ liter. With an increase in the concentration of HCl to 100 mequiv/liter, the net loss of H+ increased to -0.49 + 0.16 mequiv/min. This increase was not statistically significant. In Part B (HCl + pepsin), the loss of H+ per 30 min was increased to -0.30 + 0.07 with addition of 7500 units of pepsin to 25 mequiv/liter of HCl, and this loss was decreased to -0.23 f. 0.11 when the concentration of pepsin was increased to 15,000 units. Also the loss of H+ was increased to -0.92 + 0.09 when 7500 units of pepsin were added to 50 mequiv/liter of HCl (p < 0.002), but when the concentration of pepsin was increased to 15,000 units the H+ loss was decreased to -0.65 + 0.04 (p < 0.01). The loss of H+ was significantly increased to 2.15 ? 0.17 mequiv per 30 min (P < 0.001) when 7500 units of pepsin were added to 100 mequiv of HCl/liter, but a decline in the amount of H+ loss was noted when the concentration of pepsin was increased to 15,000 units (P < 0.01). Loss of H+ was significantly increased with a higher concentration of HCl but constant concentrations of pepsin. Chloride loss was also increased. There was a gain in potassium and sodium ions when pepsin was added to the test solution. The pC0, gain was negligible for the HCl group and the slight increase inpC0, influx when pepsin was added to HCl was not statistically significant. Esophagi of HCl-treated dogs were normal histologically, but in the pepsintreated group histologic examination of the
Ferguson et al. [2], by using canine gastric juice, pH 1.2 to 1.7, produced an esophagitis so severe that perforation occurred after 1-hr insult. Kiriluk and Merendino [6] have produced esophagitis by dripping an acid-porcine pepsin solution directly on the esophagus. Goldberg et ul. [4] have shown that HCl alone in high concentrations caused esophagitis, but at lower acid concentrations pepsin is an important factor in producing esophagitis. Although the ulcerogenic effects of acid and pepsin have been shown by these authors, the mechanism of action of pepsin and its exact role have not been evaluated in previous works. Recently we reported that a barrier to H+ is present in the esophagus of dog and man and that in the presence of bile salt the loss of hydrogen ion increased from the lumen of the esophagus. Whether this increase in loss was due to neutralization of H+ by sodium bicarbonate or simply due to back diffusion into esophageal mucosa secondary to increased permeability due to cell injury was not answered in our previous experiments [Ill. In this experiment, minimal H+ efflux is present and quite constant from the esophageal mucosa. This loss is greatly accelerated when pepsin is added to the acid solution, but increasing the concentration of pepsin to above 7500 units did not result in a higher loss of H+ from the lumen. This observation has been also reported by Goldberg et al. [4] when they observed that an increase in pepsin concentration did not increase the severity of esophagitis. Similar observations evaluating the proteolytic effect of pepsin solutions of different concentrations on the esophagus or small bowel have also been reported by others [ 1, 71. Northrop [S] explained this phenomenon on the basis of pepsin inhibitory substances
8
JOURNAL
OF SURGICAL
RESEARCH:
(peptones) formed during peptic digestion of protein, which decreases the rate of digestion. Based on Northrop’s explanation, it is possible that higher concentrations of pepsin decreased the rate of cell injury and therefore decreased the loss of H+ from the lumen. This phenomenon was observed with higher concentrations of pepsin for each concentration of HCl. Because injury to esophageal mucosa due to pepsin has been observed in this experiment and has been reported by others [4] and because the apparent pC0, influxes are similar in magnitude for both Part A (acid alone) and Part B (acid and pepsin) of this experiment, the higher loss of H+ ion from the lumen in the presence of pepsin cannot be attributed to neutralization of this ion by sodium bicarbonate moved or secreted into the lumen. Based on the presence of cell injury and lack of correlation between the amount of H+ ion loss and pC0, gain, one can postulate that injured mucosal cells become less resistant or more permeable to H+ in the presence of pepsin. Perhaps the loss of this defense mechanism accompanied by H+ efflux from the lumen may contribute to production of esophagitis in experimental animals and patients with free reflux . SUMMARY
Recently we have demonstrated that a “mucosal barrier” to H+ is present in the esophagus of dog and man and in the presence of bile this barrier becomes more permeable to Hf. In this study we measured the effect of pepsin on ionic movement across the mucosa of distally occluded canine esophagus. The rate of H+ ion loss was increased significantly (P < 0.001)
VOL. 22, NO. 1, JANUARY
1977
when two different concentrations of pepsin were added to three different concentrations of HCl. Pepsin disrupts the esophageal and this observation “mucosal barrier,” suggests that reflux esophagitis in cases of incompetent gastroesophageal sphincter may be due to increased permeability of the mucosa to H+ induced by pepsin. REFERENCES I.
2. 3.
4.
5.
6.
Driver, R. W., Chappell, R. H., and Carmichael, E. B. Effect of concentration of pepsin and differential susceptibility of jejunal segments in experimental jejunal ulcers in dog. Amer. J. Dig. Dis. 12: 166, 1945. Ferguson, D. J., et al. Studies on experimental esophagitis. Surgery 28: 1022, 1950. Gillison, E. W. et al. The significance of bile in reflux esophagitis. Surg. Gynecol. Obstet. 134: 419, 1972. Goldberg, H. I., et nl. Role of acid and pepsin in acute experimental esophagitis. Gastroenterology 56: 223, 1969. Henderson, R. D., et al. The role of bile and acid in the production of esophagitis and the motor defect of esophagitis. Ann. Thorac. Surg. 14: 465, 1972. Kiriluk, L. B., and Merendino, K. A. Comparative sensitivity of mucosa of various segments of alimentary tracts in dogs to acid-peptic action. Surgery
35: 547,
1954.
7. LeVeen, H. H. Chemical, physiological and pathological observations on role of pepsin and hydrochloric acid in production of experimental ulcers. Gastroenterology 8: 648, 1947. 8. Northrop, J. H. Effect of concentration of enzyme on rate of digestion of proteins by pepsin. J. Gen. Physiol. 2: 471, 1920. 9. Safaie-Shirazi, S., et al. Effect of aspirin, alcohol and pepsin on mucosal permeability of esophageal mucosa. Surg. Forum 25: 335, 1974. 10. Safaie-Shirazi, S., DenBesten, L., and Zike, W. L. Effect of bile salts on ionic permeability of esophageal mucosa. Surg. Forum 24: 424, 1973. 11. Safaie-Shirazi, S., DenBesten, L., and Zike, W. L. The effect of bile salts on the ionic permeability of the esophageal mucosa and their role in the production of esophagitis. Gastroenterology 68: 728, 1975.
Effect
OF SURGICAL
RESEARCH
of Pepsin
22, 5-8
on Ionic
(1977)
Permeability
of Canine
STROOS SAFAIE-SHIRAZI, Department
of Surgery,
The University
of IOWU
Submitted
for publication
Recently we have demonstrated that a barrier to H+ is present in the esophagus of the dog and man and that in the presence of bile salts this barrier is destroyed with a resultant increased loss of H+ from the esophageal lumen [9- I 11. We postulated that the high frequency of esophagitis and ulceration associated with intraesophageal bile and HCl reported in the literature [3, 51 may be due to increased permeability of the esophageal mucosa to H+ induced by bile salts. Because bile and hydrochloric acid are not the only agents present in gastric juice and because esophagitis also has been produced in animals by pepsin and HCl [2], the present study was designed to assess the effect of pepsin on the permeability of esophageal mucosa and to clarify the pathogenesis of peptic esophagitis produced by pepsin and acid. MATERIALS
AND METHODS
5 0 1977 by Academic Press, Inc. of reproduction in any form reserved.
April
Mucosa
M.D. of Medicine,
Iowa
City,
Iowu
52242
13, 1976
of 50 ml was chosen as the quantity of test solution to be used in these experiments. Test solutions contained 25, 50, or 100 mequiv per liter of HCl and 2 g per liter of polyethylene glycol (PEG) as an inert nonabsorbable dilution indicator. Pure pepsin crystals (7500 or 15,000 units) were added to each 50 ml of test solution. The rinse solution was indicator-free normal saline (NaCl). Part A (HCI alone, 14 dogs). A solution of 25, 50, or 100 mequiv/liter of HCl + 2 mg/ml of polyethylene glycol (PEG) was instilled into the esophagus. This was thoroughly mixed for 1 min by gentle injection and aspiration. A 2-ml aliquot was removed, and the remainder of the solution was left in the esophagus for 30 min. The esophageal contents were then completely aspirated, the volume was measured, and a 5-ml aliquot was saved for analysis. The esophagus was thoroughly rinsed with 100 ml of NaCl after each study; for each concentration of HCl the experiment was repeated twice. Two dogs were killed and the esophagi were examined microscopically. Part B (HCl + pepsin, 12 dogs). After 2 weeks, the 12 remaining animals were prepared for studies, as previously outlined. In four dogs 50 ml of test solution containing 25 mequiv/liter of HCl + 2 mg/ml PEG + 7500 units of pepsin was instilled into the esophagus for two periods of 30 min each. The experiment was repeated with the sameconcentration of HCl but a higher concentration of pepsin (15,000 units) for another two periods of 30 min. The same procedure was then repeated with 50 mequivl liter of HCl and two concentrations of pepsin (7500 and 15,000 units) in another
Healthy, adult mongrel dogs were anesthetized with pentobarbital, 30 mg/kg body weight. A double-lumen oro-esophageal tube was placed in the esophagus. A celiotomy was performed, the gastroesophageal junction was identified and occluded with a noncrushing vascular clamp. The esophageal tube was then positioned just proximal to the clamp. Through a high cervical incision, the esophagus was ligated with an umbilical tape just distal to the thyroid cartilage. By repeated measurements of esophageal capacity, we found that the instillation of 100 ml of saline regularly increased intraesophageal pressure by only 3 to 5 cm of saline. Therefore, a volume Copyright All rights
College
Esophageal
6
JOURNAL
OF SURGICAL
RESEARCH: TABLE
IONIC
VOL. 22, NO. I, JANUARY
1977
1
MOVEMENT IN RESPONSE TO INSTILLATION OF 25, 50, OR 100 mmol/liter CONCENTRATIONS OF PEPSIN INTO PROXIMALLY AND DISTALLY OCCLUDED
HC1 PLUS Two CANINE
DIFFERENT ESOPHAGUS
Milliliters of H,O Solution instilled HCI alone 25 mequiv -0.12 50 mequiv -0.17 100 mequiv -0.49 HCI + pepsin 25 mequiv HCl + 7500 U pepsin -0.30 25 mequiv HCI + 15,OOOUpepsin -0.23 50 mequiv HCI + 7500 U pepsin -0.92 50 mequiv HCI + 15,OOOUpepsin -0.65 100 mequiv HCI + 7500 U pepsin -2.15 100 mequiv HCl + 15,000 U pepsin -1.40
H
Cl
Na
K
flLlX
2 0.02 k 0.16 f 0.16
-0.28 -c 0.22 +0.40 2 0.16 -0.39 ” 0.25 +0.42 2 0.13 -0.31 + 0.12 +0.31 + 0.26
+0.09 2 0.07 +0.09 t 0.11 +0.16 2 0.07
2.54 3.74 1.51
2 0.07
-0.56 f 0.15 +0.75 2 0.19 +0.018 2 0.004 +0.18 2 0.07
2.11
2 0.11
-2.37 k 0.43 +2.73 f 0.41
+0.08 f 0.009
+0.22 f 0.13
3.12
t 0.09”
-0.87 + 0.08 +1.61 2 0.11
+0.04 k 0.002
+0.26 2 0.09
3.14
k 0.04”
-1.44 k 0.08 +2.22 2 0.08
+0.08 rt 0.003
+0.15 k 0.15
4.64
2 0.17”
-0.33 f 0.07 +1.55 -c 0.11
+0.04 f 0.005
+0.41 2 0.25
2.59
+0.07 f 0.006 +0.31 k 0.12
3.72
k 0.14* -0.11 2 0.08 +I.62 -e 0.09
+O.Ol +O.Ol +O.Ol
PC%
n P < 0.002. *P < 0.01. ‘P < 0.001.
four dogs and again with 100 mequiv/liver of HCI and the same concentrations of pepsin (7500 and 15,000 units) in the last remaining dogs. Between each period of experimentation the esophagus was washed with 100 ml of rinse solution (NaCl). Animals were killed, the esophagi were examined, and appropriate sections were obtained for histologic examination. Laboratory measurements and calculations. After centrifugation to obtain clear
supernatant solutions, H+, Cl-, Na+, K+, and PEG concentrations were determined in all aliquots. PEG was measured by a turbidimetric method, and H+ content was determined by titration with 0.1 N NaOH to pH 7.4 with the use of a glass electrode. Sodium and potassium concentrations were determined with a flame photometer (IL Model No. 143, Instrumental Laboratory,
Inc., Lexington, Massachusetts). Chloride concentrations were determined by a chloridometer (Buchler-Collove; Buchler Instrument Division, Nuclear Chicago Corp., Fort Lee, New Jersey). p CO, was measured with an automatic blood gas and pH meter (Model No. 3 13, Instrumental Laboratory) immediately after obtaining the aliquots. The residual volume in the esophagus and the volume secreted, if any, during each 30min period were calculated from dilution of the nonabsorbable PEG marker. The total mass of H+, Na+, K+, and Cl- present initially after mixing and at the end of the 30-min test periods was calculated by multiplying the concentration of these ions by the volume. The net flux in and out of the lumen was determined by subtracting the initial mass from the final mass. A positive
SAFAIE-SHIRAZI:
PEPSIN
AND
flux (+) indicated a net addition of ions to the lumen, and a negative flux (-) indicated a net loss of ions from the lumen. A Student’s t test was used to analyze paired observations.
ESOPHAGEAL
MUCOSA
7
esophagus showed complete epithelial erosion with proteinaceous edema and proteolytic changes involving the entire thickness of the lamina propria. DISCUSSION
RESULTS
The mean net flux of ions for each 30-min period of experimentation is shown in Table 1. In Part A (HCl alone), the mean loss of H+ was -0.12 ? 0.02 mequiv/30 min when the concentration of H+ was 25 mequiv/ liter. With an increase in the concentration of HCl to 100 mequiv/liter, the net loss of H+ increased to -0.49 + 0.16 mequiv/min. This increase was not statistically significant. In Part B (HCl + pepsin), the loss of H+ per 30 min was increased to -0.30 + 0.07 with addition of 7500 units of pepsin to 25 mequiv/liter of HCl, and this loss was decreased to -0.23 f. 0.11 when the concentration of pepsin was increased to 15,000 units. Also the loss of H+ was increased to -0.92 + 0.09 when 7500 units of pepsin were added to 50 mequiv/liter of HCl (p < 0.002), but when the concentration of pepsin was increased to 15,000 units the H+ loss was decreased to -0.65 + 0.04 (p < 0.01). The loss of H+ was significantly increased to 2.15 ? 0.17 mequiv per 30 min (P < 0.001) when 7500 units of pepsin were added to 100 mequiv of HCl/liter, but a decline in the amount of H+ loss was noted when the concentration of pepsin was increased to 15,000 units (P < 0.01). Loss of H+ was significantly increased with a higher concentration of HCl but constant concentrations of pepsin. Chloride loss was also increased. There was a gain in potassium and sodium ions when pepsin was added to the test solution. The pC0, gain was negligible for the HCl group and the slight increase inpC0, influx when pepsin was added to HCl was not statistically significant. Esophagi of HCl-treated dogs were normal histologically, but in the pepsintreated group histologic examination of the
Ferguson et al. [2], by using canine gastric juice, pH 1.2 to 1.7, produced an esophagitis so severe that perforation occurred after 1-hr insult. Kiriluk and Merendino [6] have produced esophagitis by dripping an acid-porcine pepsin solution directly on the esophagus. Goldberg et ul. [4] have shown that HCl alone in high concentrations caused esophagitis, but at lower acid concentrations pepsin is an important factor in producing esophagitis. Although the ulcerogenic effects of acid and pepsin have been shown by these authors, the mechanism of action of pepsin and its exact role have not been evaluated in previous works. Recently we reported that a barrier to H+ is present in the esophagus of dog and man and that in the presence of bile salt the loss of hydrogen ion increased from the lumen of the esophagus. Whether this increase in loss was due to neutralization of H+ by sodium bicarbonate or simply due to back diffusion into esophageal mucosa secondary to increased permeability due to cell injury was not answered in our previous experiments [Ill. In this experiment, minimal H+ efflux is present and quite constant from the esophageal mucosa. This loss is greatly accelerated when pepsin is added to the acid solution, but increasing the concentration of pepsin to above 7500 units did not result in a higher loss of H+ from the lumen. This observation has been also reported by Goldberg et al. [4] when they observed that an increase in pepsin concentration did not increase the severity of esophagitis. Similar observations evaluating the proteolytic effect of pepsin solutions of different concentrations on the esophagus or small bowel have also been reported by others [ 1, 71. Northrop [S] explained this phenomenon on the basis of pepsin inhibitory substances
8
JOURNAL
OF SURGICAL
RESEARCH:
(peptones) formed during peptic digestion of protein, which decreases the rate of digestion. Based on Northrop’s explanation, it is possible that higher concentrations of pepsin decreased the rate of cell injury and therefore decreased the loss of H+ from the lumen. This phenomenon was observed with higher concentrations of pepsin for each concentration of HCl. Because injury to esophageal mucosa due to pepsin has been observed in this experiment and has been reported by others [4] and because the apparent pC0, influxes are similar in magnitude for both Part A (acid alone) and Part B (acid and pepsin) of this experiment, the higher loss of H+ ion from the lumen in the presence of pepsin cannot be attributed to neutralization of this ion by sodium bicarbonate moved or secreted into the lumen. Based on the presence of cell injury and lack of correlation between the amount of H+ ion loss and pC0, gain, one can postulate that injured mucosal cells become less resistant or more permeable to H+ in the presence of pepsin. Perhaps the loss of this defense mechanism accompanied by H+ efflux from the lumen may contribute to production of esophagitis in experimental animals and patients with free reflux . SUMMARY
Recently we have demonstrated that a “mucosal barrier” to H+ is present in the esophagus of dog and man and in the presence of bile this barrier becomes more permeable to Hf. In this study we measured the effect of pepsin on ionic movement across the mucosa of distally occluded canine esophagus. The rate of H+ ion loss was increased significantly (P < 0.001)
VOL. 22, NO. 1, JANUARY
1977
when two different concentrations of pepsin were added to three different concentrations of HCl. Pepsin disrupts the esophageal and this observation “mucosal barrier,” suggests that reflux esophagitis in cases of incompetent gastroesophageal sphincter may be due to increased permeability of the mucosa to H+ induced by pepsin. REFERENCES I.
2. 3.
4.
5.
6.
Driver, R. W., Chappell, R. H., and Carmichael, E. B. Effect of concentration of pepsin and differential susceptibility of jejunal segments in experimental jejunal ulcers in dog. Amer. J. Dig. Dis. 12: 166, 1945. Ferguson, D. J., et al. Studies on experimental esophagitis. Surgery 28: 1022, 1950. Gillison, E. W. et al. The significance of bile in reflux esophagitis. Surg. Gynecol. Obstet. 134: 419, 1972. Goldberg, H. I., et nl. Role of acid and pepsin in acute experimental esophagitis. Gastroenterology 56: 223, 1969. Henderson, R. D., et al. The role of bile and acid in the production of esophagitis and the motor defect of esophagitis. Ann. Thorac. Surg. 14: 465, 1972. Kiriluk, L. B., and Merendino, K. A. Comparative sensitivity of mucosa of various segments of alimentary tracts in dogs to acid-peptic action. Surgery
35: 547,
1954.
7. LeVeen, H. H. Chemical, physiological and pathological observations on role of pepsin and hydrochloric acid in production of experimental ulcers. Gastroenterology 8: 648, 1947. 8. Northrop, J. H. Effect of concentration of enzyme on rate of digestion of proteins by pepsin. J. Gen. Physiol. 2: 471, 1920. 9. Safaie-Shirazi, S., et al. Effect of aspirin, alcohol and pepsin on mucosal permeability of esophageal mucosa. Surg. Forum 25: 335, 1974. 10. Safaie-Shirazi, S., DenBesten, L., and Zike, W. L. Effect of bile salts on ionic permeability of esophageal mucosa. Surg. Forum 24: 424, 1973. 11. Safaie-Shirazi, S., DenBesten, L., and Zike, W. L. The effect of bile salts on the ionic permeability of the esophageal mucosa and their role in the production of esophagitis. Gastroenterology 68: 728, 1975.