Duodenal Pepsinogens in Experimental Duodenal Ulcer in Rats

JAGDISH C. MANGLA AND MARK PEREIRA

Department of Gastroenterology, Monroe Community Hospital, 435 East Henrietta

Road, Rochester, New* York 14603

Received August II. 1981

There was not a uniformly predictable animal model for duodenal ulcer. In 1972 Dr. Szabo (I) produced duodenal ulcers by using pro- pionitrile and cysteamine (2.3). In 1979 (4) detailed investigations ’ showed that chemically induced duodenal ulcer in rats resembles the peptic ulcer disease in human beings. However, they were unable to identify the factors involved in the pathogenesis of this ulcer. This man- uscript is an attempt to elucidate the role of gastric and duodenal mucosal pepsinogens after production of duodenal ulcer in rats by cysteamine.

MATERIALS AND METHODS

We used 24 female Sprague-Dawley derived Charles River rats (Wil- mington, Mass.) weighing 150-175 g. They were divided into four groups (A. B, C, D) of six rats each. The rats were maintained on Purina Laboratory chow and tap water ad lihitum. The animals were not fasted. On the day of experiment, each of six rats in the control group (A) got 0.5 ml distilled water subcutaneously. Cysteamine hydrochloride (2- aminoethanethiol hydrochloride, mw 113.61) was obtained from Aldrich Chemical Company, Inc., Milwaukee. Wisconsin. The experimental groups (B, C, D) of six rats each got 42.5 mgi100 g. body wt of cysteamine dissolved in 0.5 ml distilled water subcutaneously. All the groups (A-D) had free access to food and water. The control group A was sacrificed at 1 hr after injection, group B at 1 hr, group C at 2 hr. and group D at 4 hr. The stomach and duodenum were isolated and cut along the greater curvature. The gastric and duodenal mucosa was scraped by the scalpel and homogenized separately in 0.1 M Sorenson’s phosphate buffer at pH 7.2. The pepsinogen content per milligram of protein was calculated by modified Anson (5) and Mirsky’s procedure (6). The protein content was found by the Lowry method (7).

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DUODENAL PEPSINOGENS 83

Statistical Analysis

The control group A was compared with experimental groups B, C, and D. The analysis of gastric mucosal pepsinogens was kept separate from duodenal pepsinogens because there was no correlation between their values. All the experimental groups were also compared to one another. Student’s t test was done to compare the results.

RESULTS Pepsinogens (mg tyrosineimg protein mean of six rats)

~- ~-- Control group A-l hr B-l hr C-2 hr D-4 hr

Duodenal mucosa 0.1866 1.6164 0.4577 0.6957

Stomach 15.827 I I.780 10.628 7.010

In conclusion, looking at the figures the study showed that cystearn& produced a marked rise of duodenal mucosal pepsinogen levels. This study also showed a declining gastric mucosal level of pepsinogens (Pig. 1).

DISCUSSION

Szabo et al. (4) have shown that duodenal ulcers induced by cys- teamine in rats resemble the human peptic ulcer disease. They also demonstrated that these ulcers were abolished by vagotomy, decreased by sympathectomy, histamine depletion, H, receptor antagonists, hy- pophysectomy, thyroidectomy, and adrenalectomy. The gastric hyper- acidity like human duodenal ulcer was reduced by metiamide or vagot- omy. This may serve as a very good model to identify factors in the causation and treatment of duodenal ulcer. Even though hyperacidity is considered an important factor, yet two-thirds of duodenal ulcer patients do not show this hypersecretory phenomenon (8). Pepsinogens may also be very important in the etiology of peptic ulcer disease. Pepsinogen is a zymogen without any proteolytic properties. Pepsinogen must be con- verted to pepsin for a proteolytic action. Acid may be essential only to activate the pepsinogens to pepsins. A study done in pylorus ligated rats (9) demonstrated that intragastric instillation of HCl failed to produce mucosal lesions which, however, could be induced in such animals by gastric juice or a mixture of hydrochloric acid and pepsin. Serum pep- sinogens correlated positively with gastric acid secretion in duodenal ulcer disease (10). An elevated serum pepsinogen concentrated was shown to a subclinical marker of ulcer diathesis (11).

The main aim of our present work was to find out if duodenal pep- sinogen levels of duodenal mucosa are altered in anyway in a cysteamine- induced duodenal ulcer. We expected lower levels of pepsinogen in duo-

x4 MANtiLA AND PERElK.

2.0 DUODENAL

I .o I i

20 - GASTRIC

5’ I I I I 0 I 2 3 4

HOURS

FIG. I. Duodenal and gastric mucosal pepsinogen levels. Abscissa denotes hours after giving 42.5 mg/lOO g body wt. 0 indicates baseline levels before giving cysteamine. Ordinate shows the results of pepsinogen levels expressed in mg of tyrosine/mg of protein. Each solid circle represents the mean of six values 2 SEM. The significance of rise at I. 2, and 4 hr is compared to basal levels at 0 hr. Value of P is expressed above the mean value.

denal mucosa because ulcerated mucosa looses some of the enzymes. We also expected normal or higher levels in gastric mucosa because of a greater degree of acid and pepsin which are secreted by gastric glands in duodenal ulceration. However, both our results were unexpected, i.e., duodenal mucosa contained more pepsinogen than control while gastric mucosa contained less pepsinogen than control. It is also interesting to note that gastric levels kept on falling up to 4 hr. They were less than 50% at 4 hr. The reason for the drop in pepsinogen level in gastric mucosa is obscure. This elevated duodenal pepsinogen level may explain why cysteamine produces duodenal ulcer and not gastric ulcer in rats.

SUMMARY

Chemically induced duodenal ulcer in rats resembles the duodenal ulcer disease in humans. The mechanism of such an ulceration is not

DUODENAL PEPSINOGENS 85

well established. This is an attempt to show that pepsinogens may play a role in such an ulceration. Twenty-four female Sprague-Dawley rats weighing 150-175 g each were divided into four groups of six rats each. The control group (A) was given 0.5 ml of distilled water subcutaneously and experimental groups were each given cysteamine (42.5 mg/lOO g body wt of rats). The rats were sacrificed at 1,2, and 4 hr. The pepsinogen content per milligram of protein was calculated in gastric and duodenal mucosa of all groups. Cysteamine produced a marked increase in duo- denal mucosal pepsinogen level: however, gastric pepsinogen levels fell and were less than half at 4 hr. This might explain why cysteamine produced only duodenal ulcers and not gastric ulcers in this experimental model.

REFERENCES

I. Szabo. S., and Selye, H., Arch. Pathol. 93, 390 (1972).

2. Selye. H., and Szabo, S., Nature (London) 244, 458 (1973). 3. Szabo, S., Amer. J. Pathol. 93, 273 (1978).

4. Szabo. S., Haith, L. R.. and Reynolds, E. S.. Dig. Dis. Sci. 24, 471 (1979). 5. Mangla, J. C., Guarasci. G.. and Turner, M. D.. Amer. J. Dig. Dis. 18, 857 (1973). 6. Anson, M. L.. and Mirsky, A. E.. J. Gen. Physiol. 16, 59 (1932). 7. Lowry, 0. H., Rosebrough, N. J.. Farr. A. L.. and Randall. R. J., J. Biol. Chem.

193, 265 (1951). 8. Wormsley, K., and Grossman, M.. Cur 6, 427 (1965). 9. Pallares, J., Scarselli, V., Arch. In?. Pharmacodyn. Ther. 192, 37 (1971).

IO. Samloff, I. M., Secrist, D. M., and Passaro, E., Gastroenterology 69, 1196. (1975). I I. Rotter. J. I.. Sones, J. Q.. Samloff, M.. ef rrl.. N. Enpl. J. Med. 300, 63 (1979).