Physiology & Behavior, Vol. 19, pp. 315--317. Pergamon Press and Brain Research Publ., 1977.

Printed in the U.S.A.

Vendor Differences in Starvation-Induced Gastric Ulceration WILLIAM P. PARIS, GARY B. GLAVIN 2 AND GEORGE P. VINCENT

Pavlovian Laboratory, Veterans Administration Hospital, Perry Point, MD 21902 (Received 2 February 1977) PARE, W. P., G. B. GLAVIN AND G. P. VINCENT. Vendor differences in starvation-induced gastric ulceration. PHYSIOL. BEHAV. 19(2) 315-317, 1977. - - The incidence of starvation-induced gastric lesions was observed in Sprague-Dawley rats obtained from four different vendors (ARS/Sprague-Dawley, Hilltop, Holtzman, and Charles River). Food was withheld for 5 days from rats weighing 150, 200,260 or 330 g. Glandular lesions occurred in 150 g rats; rumenal lesions occurred in 200+ rats. ARS/Sprague-Dawley rats developed more glandular lesions, whereas Hilltop rats developed more rumenal lesions. Ulcer

Starvation

Animal vendors

IN CONDUCTING a research project, most investigators are satisfied to control for the strain, sex and weight distribution of their animal subjects. When studies are to be replicated, investigators try to use the same strain of rats which was used in the original study. This, however, was not always the case. The literature on conflict-induced lesion reveals studies in which different rat strains were used. Using the Sawrey-Weisz conflict procedure, some investigators used Sprague-Dawley rats [1,12] whereas other studies reported the use of hooded rats [2,14]. In an earlier study, Par6 [7] demonstrated that Long Evans rats were more susceptible, and Wistar rats more resistant to ulcers induced by the Sawrey-Weisz conflict procedure. It would be expected that if strain, sex, age and weight were controlled, replication discrepancies would be attributable only to procedural variations between investigators. However, recent reports suggest that this may not always be the case. Studies on the ulcerogenic effects of unpredictable shock have not always produced similar results even though the same strain of rats was used [3, 11, 15]. In 1972, Par6 reported a study which failed to replicate the findings of an earlier study [ 13] even though similar rat strains were used in both studies. One explanation advanced to explain these discrepant results was the fact that the animals for both studies were obtained from different suppliers and this difference in vendors may have accounted for the lack of agreement between the two studies [7]. In these studies, the possibility exists that same-strain discrepancies may be attributable to the fact that researchers, working on the same problem, obtain their animals from different vendors. A report by Levine [4] supports this notion. Levine found that following administration of Brocresine - a drug which inhibits histidine decarboxylase, the enzyme that catalyzes histamine synthesis - the degree

of reduction of histamine levels in the gastric mucosa varied depending upon the three vendors of his Sprague-Dawley rats. Since histamine is an important variable in gastric ulcerogenesis [5,6] one would suspect that ulcer susceptibility in Sprague-Dawley rats would be influenced by where the rats were obtained - which vendor supplied the rats. The purpose of this study was to examine vendor differences in ulcer susceptibility. In the present study, susceptibility to starvation-induced ulcers was examined in rats of the same strain but obtained from four different vendors. METHOD The literature pertaining to stress-induced ulcers in animals was surveyed for the past 16 years. Information recorded included the rat strain used and the vendor who supplied the animals. In many cases, authors failed to report the vendor from which they obtained their animals. The most frequently used strain was Sprague-Dawley, and they were most frequently obtained from the following four vendors: ARS/Sprague-Dawley (Madison, WI), Charles River (Wilmington, MA), Holtzman (Madison, WI) and Hilltop Laboratories (Scottsdale, PA).

Animals Animals consisted of 160 male Sprague-Dawley rats. Forty rats were obtained from each of the four vendors cited above. These rats were 1 2 5 - 1 3 6 g when they were received from the vendors.

Procedure All rats were individually housed in standard single

1Supported by the Medical Research Service of the Veterans Administration. 2Currently at Brock University, St. Catharine's, Ontario, Canada. 315

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PARI~, G L A V I N A N D V I N C E N T

laboratory cages upon receipt from the vendors, and were allowed continuous access to food and water. The ulcerogenic procedure consisted simply of 5 days of c o m p l e t e f o o d deprivation [8,9]. However, the deprivation procedure started at different developmental stages for these animals. Animals in each vendor group were r a n d o m l y assigned to one of four subgroups. These subgroups represented four specific body weights at which point the deprivation p l o c e d u r e would be initiated. Body weight groups were 150 g, 200 g, 260 g and 330 g. When a rat reached its assigned body weight, it was placed on the 5-day deprivation schedule. Thus, in this e x p e r i m e n t we had rats from each vendor which were starved for 5 days when they reached either 150, 200, 260 or 3 3 0 g . The starvation procedure was applied to rats of different b o d y weights because some evidence suggests that starvation has a differential effect in terms of stomach pathology depending on whether the starvation procedure is applied to y o u n g rats as opposed to larger adult rats [ I 0 ] . After 5 days o f food deprivation, the rats were weighed and sacrificed with chloroform. The stomach was removed and cut open along the greater curvature. The stomach was rinsed with water, spread and pinned on a flat surface and covered with 10% Formalin to fix the stomach in a flat attitude. The stomach was e x a m i n e d with a binocular dissecting microscope. One eyepiece was fitted with a reticle permitting lesions to be quantified in terms of millimeters of abnormal tissue. The number, location (glandular vs. r u m e n ) and size of lesions were recorded. RESULTS Within each weight range there were no significant differences in absolute body weight loss between vendor groups. In terms of absolute body weight loss, the heavier animals lost more weight than the smaller animals. The mean absolute body weight loss for the 150 g, 200 g, 260 g, and 330 g groups was 59.9 g, 67.5 g, 72.4 g and 72.2 g, respectively. However, in terms of percent b o d y weight loss, the smaller animals lost more weight with the 150 g, 200 g, 260 g, and 330 g groups losing 39.9%, 33.7%, 27.8% and 21.9% body weight, respectively.

TABLE 1 SUMMARY OF STOMACH PATHOLOGY FOR THE FOUR PREDEPRIVATION BODY WEIGHT CONDITIONS Pathology

Pre-Deprivation Body Weights

Variables Number of rats with lesions Mean number of rumenal lesions Cumulative length (mm) Mean number of glandular lesions Cumulative length (mm)

150*

200*

260*

330*

35

22

18

17

0.95 2.73

2.37 6.95

4.05 5.47

3.65 4.27

19.05 19.4

2.70 5.3

0.0 0.0

0.0 0.0

*n = 40.

A significant difference in the n u m b e r of glandular lesions across weight ranges was observed F(3,143) = 47.9, p < 0 . 0 0 1 . Virtually all glandular lesions occurred in the 150 g weight c o n d i t i o n (see Table 1). Significant differences in the cumulative length of glandular lesions were observed. This was related in a significant way, not only to the vendors from which rats were obtained, F(3,143) = 5.50, p < 0 . 0 0 1 , but also to the weight of the rat at the beginning of starvation, F ( 3 , 1 4 3 ) = 28.10, p < 0 . 0 0 1 . These data are recorded in Table 2. Within the 150 g condition, ARS/Sprague-Dawley rats developed significantly more glandular lesions, while the Hilltop rats seemed more resistant to this form of ulceration [Tukey (a) test]. Significant vendor differences also occurred in terms of the number, F(3,143) = 4.2, p < 0 . 0 1 , and cumulative length, F(3,143) = 6.5, p < 0 . 0 1 , of rumenal lesions. Hilltop rats developed significantly more rumenal lesions, whereas ARS/Sprague-Dawley rats developed the least a m o u n t of rumenal lesions [Tukey (a) t e s t l .

TABLE 2 MEAN CUMULATIVE LENGTH OF RUMENAL AND GLANDULAR LESIONS FOR ARS, CR, H, AND Ht* RATS AT EACH PREDEPRIVATION BODY WEIGHT CONDITION Mean Cumulative length Pre-

Deprivation Body Weight 150 200 260 330 Mean

ARS 1.1 2.1 0.9 2.5 1.6

Rumenal Lesions CR H 4.6 2.8 6.2 3.3 1.7 2.4 2.9 8.2 3.9

*ARS--A RS/Sprague-Dawle y. CR--Charles River. H--Holtzman.

Ht--Hilltop.

4.2

Ht 2.4 16.2 16.9 3.5

ARS 36.8 10.2 0.0 0.0

9.7

11.8

Glandular Lesions CR H 13.1 16.7 1.9 9.1 0.0 0.0 0.0 0.9 3.8

6.6

Ht I1.1 0.0 0.0 0.0 2.8

ANIMAL VENDORS AND GASTRIC ULCER

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T h e o n l y d e a t h s w h i c h o c c u r r e d in r e s p o n s e to 5 d a y s o f s t a r v a t i o n were a m o n g rats in t h e 150 g w e i g h t c o n d i t i o n . T h e f r e q u e n c y of d e a t h s was significantly h i g h e r a m o n g H o l t z m a n a n d A R S / S p r a g u e - D a w l e y rats, w i t h e a c h g r o u p having f o u r deaths, as c o m p a r e d w i t h Hilltop a n d Charles River rats w h i c h h a d 0 a n d 1 d e a t h , respectively, x 2 ( 1 ) = 5.89, p < 0 . 0 2 . DISCUSSION G l a n d u l a r u l c e r a t i o n o c c u r r e d a l m o s t exclusively in l i g h t e r rats. This o b s e r v a t i o n is c o n s i s t e n t w i t h the s t u d y r e p o r t e d b y Pfeiffer, D e b r o and Muller [ 10]. In t h a t s t u d y ,

t h e a u t h o r s n o t e d t h a t glandular u l c e r a t i o n in r e s p o n s e to s t a r v a t i o n o c c u r r e d in weanling rats (21 days of age), while r u m e n a l u l c e r a t i o n was o b s e r v e d in older rats ( 2 4 - 1 8 0 days o f age). T h e data f r o m the p r e s e n t s t u d y f u r t h e r localize this reversal o f ulcer l o c a t i o n in r e s p o n s e to s t a r v a t i o n , in t h a t it seems to o c c u r b e t w e e n the weight ranges of 1 5 0 - 2 0 0 g. The v e n d o r d i f f e r e n c e s observed in this s t u d y suggest t h a t this variable s h o u l d be given careful p r e e x p e r i m e n t a l c o n s i d e r a t i o n iri o r d e r to avoid the i n d i s c r i m i n a t e choice o f e i t h e r a n u n u s u a l l y susceptible or u n u s u a l l y resistant a n i m a l for studies where gastric u l c e r a t i o n is involved.

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8. Par~, W. P. and L. J. Temple. Food deprivation, shock stress and stomach lesions in the rat. Physiol. Behav. 11: 371-375, 1973. 9. Peters, J. M. and E. M. Boyd. Organ weights and water contents during acute starvation, thirst and stress. Growth 32: 283-296, 1968. 10. Pfeiffer, C. J., J. R. Debro and P. J. Muller. Gastric pathologic and biochemical changes induced by starvation of weanling rats. LifeSci. 5: 5 0 9 - 5 1 9 , 1966. 11. Price, K. P. Predictable and unpredictable shock: Their pathological effects on restrained and unrestrained rats. Psychol. Rep. 30: 4 1 9 - 4 2 6 , 1972. 12. Sawrey, J. M. and W. L. Sawrey. Age, weight and social effects on ulceration rate in rats. J. comp. physioL Psychol. 49: 2 6 9 - 2 7 0 , 1956. 13. Sawrey, W. L. and D. H. Long. Strain and sex differences in ulceration in the rat. J. cornp, physiol. Psychol. 55: 603-605, 1962. 14. Sawrey, W. L. and J. D. Weisz. An experimental method of producing gastric ulcers. J. cornp, physiol. Psychol. 49: 269-270, 1956. 15. Weiss, J. M. Somatic effects of predictable and unpredictable shock. Psychosom. Med. 52: 3 9 7 - 4 0 8 , 1970.