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Inhibition by Pregnancy and Lactation of Steroidinduced Ulcers in the Rat
Vo!' 56, No.1 Printed in U.S.A.
GASTROENTEROLOGY
Copyright C 1969 by The William. & Wilkin. Co.
INHIBITION BY PREGNANCY AND LACTATION OF STEROIDINDUCED ULCERS IN THE RAT PAUL KELLY AND ANDRE ROBERT, M.D., PH.D.
Department of Biology, Western Michigan University, and Experimental Biology, The Upjohn Company, Kalamazoo, Michigan
In nonpregnant fed rats, a 4-day treatment with prednisolone produced gastric ulcers. These ulcers were reduced by about 50% throughout pregnancy and lactation, except for ulcer inhibition reaching 90% between 14 and 18 of pregnancy. Pseudopregnancy did not prevent ulcer formation. It is proposed that ovarian hormones, secreted in greater amounts during pregnancy and lactation, may be chiefly responsible for the antiulcer activity observed. Pregnancy is beneficial to ulcer patients to the extent that a pregnant woman with an ulcer is a rarity. I, 2 Symptoms and objective signs usually disappear within the first 3 to 4 weeks of pregnancy, and the protection persists until term. :J Although this beneficial effect has been known for decades and is well documented, very few studies have been performed to explain its mechanism. In the experiments reported here, we have studied the effect of pregnancy and lactation on ulcers produced in rats by administration of prednisolone (steroidinduced ulcers).
prednisolone. After 4 days of treatment, the animals were killed with chloroform, the stomachs dissected out, coded, and mixed to prevent immediate identification. They were opened along the greater curvature and examined with 2 X binocular magnifier for the presence of ulcerations. These were found in the glandular portion of the stomach (the corpus only, never the antrum) and were expressed in terms of an "ulcer index" 4.5 which is the sum of (a) the incidence, divided by 10, of animals with ulcer, (b) the average severity per group in pluses (from a scale of 0 to 3+ and (c) the average number of ulcers per stomach. Severity for a given stomach was that of the most severe ulcer for that stomach. The susceptibility to ulcer formation was tested at various times during pregnancy. The 4-day treatment with prednisolone was started, in different groups of animals, on days 0, 3, 7, 11, 14, and 17 of pregnancy, and on days 1, 8, and 14 postpartum (with and without lactation for the last two intervals). The number of animals used for each time interval ranged from 8 to 12, and is indicated in figure 1. For each time interval, a group of 12 to 15 nonpregnant rats receiving for 4 days the same dose of prednisolone (25 mg per kg) was added; these nonpregnant animals were considered the control groups. The results were expressed as per cent inhibition by comparing the "ulcer index," and its components, of a pregnant group with that of the contemporary nonpregnant group. Pseudopregnancy . In a separate experiment, the influence of pseudopregnancy on steroidinduced ulcers was studied. Vaginal smears
Methods Mating. Female Sprague-Dawley rats of initial body weight of 190 to 220 g were used. A vaginal smear was made in the afternoon and each rat found to be in proestrus was placed in a cage with 2 males. The next morning, another vaginal smear was made and the animals in which sperm was found were kept and considered pregnant (day 0 of pregnancy). Production of ulcers. Gastric ulcers were produced by injecting 25 mg per kg of prednisolone subcutaneously, once a day for 4 days. Purina Laboratory chow and water were given ad libitum during administration of Received April 15, 1968. Accepted July 8, 1968. Address requests for reprints to: Dr. Andre Robert, Experimental Biology, The Upjohn Company, Kalamazoo, Michigan 49001. 24
January
25
STEROID-INDUCED ULCERS IN THE RA T
1969
most totally prevented (90% inhibition) (fig. 1) . Ulcers were also reduced by 50% during lactation, but were not inhibited when the mothers were not lactating, that is, when the pups were removed at birth (fig. 1). Figure 2 indicates the per cent inhibition of each component of the "ulcer index." It shows that, for the most part, each component was reduced by pregnancy and lactation in proportion with the ulcer index. The only conspicuous exception is the low incidence of ulcer on day 15, a fact that is not explained and would have to be confirmed. Figure 3 illustrates the protective action of pregnancy against steroid-induced ulcers. Contrary to pregnancy, pseudopregnancy did not prevent ulcer formation (table 1) . Pregnant and lactating .rats consumed more food and water than the controls. The difference became significant from the third day for food and the fifth day for water (fig. 4). The increase was slight during the first 2 weeks of pregnancy (up to 1.5-fold) and reached 2-fold near the end of pregnancy. After 5 to 7 days of lactation, the increase in food and water consumption was much more
were made at 10 AM and the rats found to be in the estrus phase were rendered pseudopregnant between 1 and 2 PM of the same day by introducing an electrode into the vagina and delivering an electric shock for 10 sec (50 volts, 1.5 rna, dc) following the method of Staples.6 The state of pseudopregnancy was verified by vaginal smears made every other day. ill the rat, pseudopregnancy lasts about 12 days. Prednisolone was administered subcutaneously at the dose of 25 mg per kg for 4 days, from day 6 through day 9, and the animals were killed on day 10 of pseudopregnancy. Food and water were given ad libitum. Food and water intake. Since the amount of gastric contents may affect susceptibility to ulcer formation, food and water consumption was measured, in separate experiments, during pregnancy and for 7 days postpartum (with and without lactation). Measurements beyond the tenth day postpartum are increasingly less reliable since some pups are often capable by that time of jumping into the food jar. The values were compared with those of nonpregnant animals.
Results Ulcers were inhibited by about 50% in all periods of pregnancy, except when prednisolone was administered from days 14 to 17, at which time ulcers were al100
80
MATING
PARTURITION
1
(II)
1
z
Q
l-
i!! :z:
60 (9)
~
-~~-="""""ULACTATION
.... a::
(12)
:: 40 ~
20
o
4
7
"
15
18
DAYS
21
26
FIG. 1. Effect of pregnancy and lactation on steroid-induced ulcers. Horizontal lines preceding each point on the curve indicate duration of treatment (4 days) with prednisolone (25 mg per kg, subcutaneously). For each time interval, the degree of inhibition is expressed in percentage when compared with control groups receiving prednisolone but not pregnant; these control groups are represented by the abscissa (that is, 0% inhibition). The numbers in parentheses indicate the number of pregnant animals for each time interval.
Vol. 56, No.1
KELL Y AND ROBERT
26 100
PARTURITION
MATING
1
1
80
,
~ 60
0'
~
al
I
1
~
1
~40
1
1
1
1
/
0............... ...a
,..; .0 __ ..... _ ..
, Il
1
0 '
20
0
, ,,
/
\
INCIDENCE SEVERITY ULCER I STOMACH
0
4
7
/
/ \
/
II
---
I
\
\
\
,/
/ / /
--0/ \
,,
\ I \/0
,/
,/
--0
/'
LACTATION
NO LACTATION
I
--15
18 DAYS
21
26
32
39
FIG. 2. Effect of pregnancy and lactation on the components of the ulcer index. For each time interval, the degree of inhibition is expressed in percentage when compared to control groups receiving prednisolone but not pregnant; these control groups are represented by the abscissa (that is, 0% inhibition).
marked and averaged 2.5-fold. In a separate experiment, in which the pups were removed at birth, food and water consumption returned to normal 24 hr after parturition.
Discussion These results show that pregnancy and lactation markedly inhibit steroid-induced ulcers in the rat and that these ulcers can be produced again within 1 week after parturition if the mother does not lactate. Such inhibition is reminiscent of the relief from ulcer regularly seen during pregnancy in humans. The present data do not indicate whether steroid-induced ulcers in the rat resemble spontaneous duodenal ulcers in humans, but although the pathogenesis of both kinds of ulcers is likely to be different, it is significant that their development is curtailed by the same condition, namely pregnancy. Clark3 reported from a total of 313 pregnancies that 88% of the women with peptic ulcer became asymptomatic during pregnancy, but that 75 % of them had a recurrence within 6 month postpartum, and almost 100% after 2 years. Kahlson et al. 7 found that in the rat pregnancy prevented acute gastric lesions
produced by an intraperitoneal injection of a mast cell discharger, polymyxin B, and that the protection was most marked during the last 3 days of pregnancy. Our results differ from those of Kahlson and his co-workers in that (a) the type of gastric lesion produced is of a different nature (massive and sudden hemorrhagic necrosis of large segments of the mucosa in the case of polymyxin, as opposed, in our experiments, to localized crater formation appearing after 3 to 4 days of prednisolone treatment); (b) steroidinduced ulcers were inhibited throughout pregnancy, even during the first week, with maximum protection between days 14 and 18, whereas protection against polymyxin lesions was limited to the last 3 days of pregnancy7; (c) lactation protected both types of lesions with this important difference: polymyxin-induced lesions were not prevented beyond the fourth day of lactation whereas steroidinduced ulcers were inhibited at least up to 18 days of lactation (fig. 1). Kahlson et al. 7 also found that during pregnancy the presence of the fetus, although not that of the placenta, was essential for the antiulcer effect (a single fetus sufficed to prevent the gastric lesion). In
January 1969
STEROID-INDUCED ULCERS IN THE RA T
27
FIG. 3. Effect of late pregnancy on steroid-induced ulcers. View of stomach opened along greater curvature. A, control, untreated and nonpregnant. B, prednisolone, nonpregnant. Numerous deep ulcers in the glandular portion. C, prednisolone from days 14 through 17 of pregnancy, animals killed on day 18. Complete prevention of ulcers. TABLE
1. Effect of pseudopregnancy on steroidinduced ulcers· I
III
II
ConControl trol vehicle prednisolone
+
+
IV PseuPregdopregnant nant + I.'redprednisolone mso)one
+
No. of animals .. . .
6
15
21
--17
Ulcers Incidence (% ). Severity (0 to
0
73
76
35
-- - ---
3+) .....
No. per stomach Ulcer index. Change from group II (%).
0
-
--
0.7 2.7
0.7 2.3
0.3 l.1
10.7
10.6
4.9
-1
-54
• Prednisolone (25 mg per kg) started on day 6 of either pseudopregnancy or pregnancy and administered for 4 days.
the case of steroid-induced ulcers, the respective role of the fetus and the placenta was not determined; their presence, however, does not seem necessary, since ulcers were prevented during the first 4 days of pregnancy (that is, before implantation of the blastocyst) as well as during prolonged lactation (that is, after fetus and placenta had been expulsed) . The mechanism by which pregnancy and lactation protect against ulcer formation is unknown. Ovarian hormones may contribute to the antiulcer effect of pregnancy, as suggested by the observation that the preponderance of peptic ulcer in men holds true only during the child bearing age (e.g., when secretion of ovarian hormones is highest) . Before puberty, the incidence is about the same in both sexes and with the onset
KELLY AND ROBERT
28 GRAMS/DAY
50
40
FOOD INTAKE PARTURITION
MATING
1
1
30
t
r~
J.t i
20 /
CONTROLS
10
FLUID INTAKE
MLlOAY
100 MATING
80
1
60
/
CONTROLS
20
o'---5=---!-o----!,--,--~0-~15---;::20~---;2;;-5-~30 DAYS
FIG. 4. Food and water intake during pregnancy and lactation. During pregnancy, from days 0 through 3 for food, and from days 0 through 5 for water, values between both groups are not statistically different. Beyond these days, the difference be· tween both groups are statistically different (P < 0.01), except on day 2 postpartum.
of menopause the incidence in females increases sharply. 1. 3 Fajer and BarracloughS reported that progesterone secretion during pregnancy in the rat reaches a peak on days 13 to 15, and it is at that time (days 14 to 18) that steroid ulcer inhibition was highest (fig. 1). The fact, however, that pseudopregnancy did not reduce steroid ulcer formation in the rat does not support an antiulcer effect mediated by ovarian hormones. Pregnancy may alter gastric secretion in such a way that corticoids cannot induce ulcers easily anymore. However, Lilja and Svensson 9 found a sharp increase in acid secretion during pregnancy and lactation in the rat, both basal and stimulated with histamine or gastrin, from the first week of pregnancy onward,
Vol. 56, No . 1
with a peak in the third week. Therefore, the antiulcer effect of pregnancy in the rat cannot be ascribed to a reduction in acid secretion. In previous studies 4 • 5 on steroid-induced ulcers, the animals were fasted during treatment with prednisolone, whereas in the present experiments they were fed throughout. This change in technique was made because it was feared that fasting for 4 days, in addition to prednisolone administration, might interfere with pregnancy. As a consequence, the ulcers were not so severe as in fasted rats; however, at autopsy the fetuses, removed while the mothers were still breathing, were alive, and the ad libitum feeding permitted us to correlate the amount of daily food intake with ulcer formation. Food intake was increased from the third day of pregnancy and during lactation (fig. 4) . The increased food in the stomach could have acted as a buffer to gastric secretion and thereby prevented erosion of the mucosa. It is unlikely, however, that this factor played a significant role, because the degree of ulcer inhibition was the same (50%) during the first 4 days of pregnancy, at which time food and water intake were not increased significantly, as during the midportion of pregnancy, when the intake was increased. Moreover, if the increase in food and water intake had played a major part in preventing ulcer formation , the greatest protection should have taken place during lactation (which was not the case), since at that time the animals were ingesting up to 2.5 times as much food and water as the controls. Food and water intake was not measured during pseudopregnancy. REFERENCES 1. Sandweiss, D. J. , H. C. Saltztein, and A. A. Farbman. 1939. The relation of sex hormones to peptic ulcer. Amer. J. Dig. Dis. 6: 6-12. 2. Bockus, H. L. 1963. Gastroenterology, Ed. 2, Vol. 1, p. 467. W. B. Saunders Company, Philadelphia. 3. Clark, D. H. 1953. Peptic ulcer in women. Brit. Med . J. 1: 1254-1257. 4. Robert, A., and J. E. Nezamis. 1958. Ulcerogenic
January 1969
STEROID-INDUCED ULCERS IN THE RA T
property of steroids. Proc . Soc. Exp. Biol. Med. 99: 443-447. 5. Robert, A., and J . E . Nezamis. 1964. Histopathology of steroid-induced ulcers. Arch. Path. (Chicago) 77: 407-423. 6. Staples, R. E. 1965. Induction of pseudopregnancy in the rat by vaginal stimulation at various stages of the estrous cycle. Anat. Rec. 152: 499-502. 7. Kahlson, G. , B. Lilja, and S. E. Svensson. 1964.
29
Physiological protection against gastric ulceration during pregnancy and lactation in the rat. Lancet 2: 1269-1272. 8. Fajer, A. B., and C. A. Barraclough . 1967. Ovarian secretion of progesterone and ",-hydroxypregn4-en-3-one during pseudopregnancy and pregnancy in rats. Endocrinology 81: 617-622. 9. Lilja, B., and S. E. Svensson. 1967. Gastric secretion during pregnancy and lactation in the rat. J. Physiol. (London) 190: 261-272.
GASTROENTEROLOGY
Copyright C 1969 by The William. & Wilkin. Co.
INHIBITION BY PREGNANCY AND LACTATION OF STEROIDINDUCED ULCERS IN THE RAT PAUL KELLY AND ANDRE ROBERT, M.D., PH.D.
Department of Biology, Western Michigan University, and Experimental Biology, The Upjohn Company, Kalamazoo, Michigan
In nonpregnant fed rats, a 4-day treatment with prednisolone produced gastric ulcers. These ulcers were reduced by about 50% throughout pregnancy and lactation, except for ulcer inhibition reaching 90% between 14 and 18 of pregnancy. Pseudopregnancy did not prevent ulcer formation. It is proposed that ovarian hormones, secreted in greater amounts during pregnancy and lactation, may be chiefly responsible for the antiulcer activity observed. Pregnancy is beneficial to ulcer patients to the extent that a pregnant woman with an ulcer is a rarity. I, 2 Symptoms and objective signs usually disappear within the first 3 to 4 weeks of pregnancy, and the protection persists until term. :J Although this beneficial effect has been known for decades and is well documented, very few studies have been performed to explain its mechanism. In the experiments reported here, we have studied the effect of pregnancy and lactation on ulcers produced in rats by administration of prednisolone (steroidinduced ulcers).
prednisolone. After 4 days of treatment, the animals were killed with chloroform, the stomachs dissected out, coded, and mixed to prevent immediate identification. They were opened along the greater curvature and examined with 2 X binocular magnifier for the presence of ulcerations. These were found in the glandular portion of the stomach (the corpus only, never the antrum) and were expressed in terms of an "ulcer index" 4.5 which is the sum of (a) the incidence, divided by 10, of animals with ulcer, (b) the average severity per group in pluses (from a scale of 0 to 3+ and (c) the average number of ulcers per stomach. Severity for a given stomach was that of the most severe ulcer for that stomach. The susceptibility to ulcer formation was tested at various times during pregnancy. The 4-day treatment with prednisolone was started, in different groups of animals, on days 0, 3, 7, 11, 14, and 17 of pregnancy, and on days 1, 8, and 14 postpartum (with and without lactation for the last two intervals). The number of animals used for each time interval ranged from 8 to 12, and is indicated in figure 1. For each time interval, a group of 12 to 15 nonpregnant rats receiving for 4 days the same dose of prednisolone (25 mg per kg) was added; these nonpregnant animals were considered the control groups. The results were expressed as per cent inhibition by comparing the "ulcer index," and its components, of a pregnant group with that of the contemporary nonpregnant group. Pseudopregnancy . In a separate experiment, the influence of pseudopregnancy on steroidinduced ulcers was studied. Vaginal smears
Methods Mating. Female Sprague-Dawley rats of initial body weight of 190 to 220 g were used. A vaginal smear was made in the afternoon and each rat found to be in proestrus was placed in a cage with 2 males. The next morning, another vaginal smear was made and the animals in which sperm was found were kept and considered pregnant (day 0 of pregnancy). Production of ulcers. Gastric ulcers were produced by injecting 25 mg per kg of prednisolone subcutaneously, once a day for 4 days. Purina Laboratory chow and water were given ad libitum during administration of Received April 15, 1968. Accepted July 8, 1968. Address requests for reprints to: Dr. Andre Robert, Experimental Biology, The Upjohn Company, Kalamazoo, Michigan 49001. 24
January
25
STEROID-INDUCED ULCERS IN THE RA T
1969
most totally prevented (90% inhibition) (fig. 1) . Ulcers were also reduced by 50% during lactation, but were not inhibited when the mothers were not lactating, that is, when the pups were removed at birth (fig. 1). Figure 2 indicates the per cent inhibition of each component of the "ulcer index." It shows that, for the most part, each component was reduced by pregnancy and lactation in proportion with the ulcer index. The only conspicuous exception is the low incidence of ulcer on day 15, a fact that is not explained and would have to be confirmed. Figure 3 illustrates the protective action of pregnancy against steroid-induced ulcers. Contrary to pregnancy, pseudopregnancy did not prevent ulcer formation (table 1) . Pregnant and lactating .rats consumed more food and water than the controls. The difference became significant from the third day for food and the fifth day for water (fig. 4). The increase was slight during the first 2 weeks of pregnancy (up to 1.5-fold) and reached 2-fold near the end of pregnancy. After 5 to 7 days of lactation, the increase in food and water consumption was much more
were made at 10 AM and the rats found to be in the estrus phase were rendered pseudopregnant between 1 and 2 PM of the same day by introducing an electrode into the vagina and delivering an electric shock for 10 sec (50 volts, 1.5 rna, dc) following the method of Staples.6 The state of pseudopregnancy was verified by vaginal smears made every other day. ill the rat, pseudopregnancy lasts about 12 days. Prednisolone was administered subcutaneously at the dose of 25 mg per kg for 4 days, from day 6 through day 9, and the animals were killed on day 10 of pseudopregnancy. Food and water were given ad libitum. Food and water intake. Since the amount of gastric contents may affect susceptibility to ulcer formation, food and water consumption was measured, in separate experiments, during pregnancy and for 7 days postpartum (with and without lactation). Measurements beyond the tenth day postpartum are increasingly less reliable since some pups are often capable by that time of jumping into the food jar. The values were compared with those of nonpregnant animals.
Results Ulcers were inhibited by about 50% in all periods of pregnancy, except when prednisolone was administered from days 14 to 17, at which time ulcers were al100
80
MATING
PARTURITION
1
(II)
1
z
Q
l-
i!! :z:
60 (9)
~
-~~-="""""ULACTATION
.... a::
(12)
:: 40 ~
20
o
4
7
"
15
18
DAYS
21
26
FIG. 1. Effect of pregnancy and lactation on steroid-induced ulcers. Horizontal lines preceding each point on the curve indicate duration of treatment (4 days) with prednisolone (25 mg per kg, subcutaneously). For each time interval, the degree of inhibition is expressed in percentage when compared with control groups receiving prednisolone but not pregnant; these control groups are represented by the abscissa (that is, 0% inhibition). The numbers in parentheses indicate the number of pregnant animals for each time interval.
Vol. 56, No.1
KELL Y AND ROBERT
26 100
PARTURITION
MATING
1
1
80
,
~ 60
0'
~
al
I
1
~
1
~40
1
1
1
1
/
0............... ...a
,..; .0 __ ..... _ ..
, Il
1
0 '
20
0
, ,,
/
\
INCIDENCE SEVERITY ULCER I STOMACH
0
4
7
/
/ \
/
II
---
I
\
\
\
,/
/ / /
--0/ \
,,
\ I \/0
,/
,/
--0
/'
LACTATION
NO LACTATION
I
--15
18 DAYS
21
26
32
39
FIG. 2. Effect of pregnancy and lactation on the components of the ulcer index. For each time interval, the degree of inhibition is expressed in percentage when compared to control groups receiving prednisolone but not pregnant; these control groups are represented by the abscissa (that is, 0% inhibition).
marked and averaged 2.5-fold. In a separate experiment, in which the pups were removed at birth, food and water consumption returned to normal 24 hr after parturition.
Discussion These results show that pregnancy and lactation markedly inhibit steroid-induced ulcers in the rat and that these ulcers can be produced again within 1 week after parturition if the mother does not lactate. Such inhibition is reminiscent of the relief from ulcer regularly seen during pregnancy in humans. The present data do not indicate whether steroid-induced ulcers in the rat resemble spontaneous duodenal ulcers in humans, but although the pathogenesis of both kinds of ulcers is likely to be different, it is significant that their development is curtailed by the same condition, namely pregnancy. Clark3 reported from a total of 313 pregnancies that 88% of the women with peptic ulcer became asymptomatic during pregnancy, but that 75 % of them had a recurrence within 6 month postpartum, and almost 100% after 2 years. Kahlson et al. 7 found that in the rat pregnancy prevented acute gastric lesions
produced by an intraperitoneal injection of a mast cell discharger, polymyxin B, and that the protection was most marked during the last 3 days of pregnancy. Our results differ from those of Kahlson and his co-workers in that (a) the type of gastric lesion produced is of a different nature (massive and sudden hemorrhagic necrosis of large segments of the mucosa in the case of polymyxin, as opposed, in our experiments, to localized crater formation appearing after 3 to 4 days of prednisolone treatment); (b) steroidinduced ulcers were inhibited throughout pregnancy, even during the first week, with maximum protection between days 14 and 18, whereas protection against polymyxin lesions was limited to the last 3 days of pregnancy7; (c) lactation protected both types of lesions with this important difference: polymyxin-induced lesions were not prevented beyond the fourth day of lactation whereas steroidinduced ulcers were inhibited at least up to 18 days of lactation (fig. 1). Kahlson et al. 7 also found that during pregnancy the presence of the fetus, although not that of the placenta, was essential for the antiulcer effect (a single fetus sufficed to prevent the gastric lesion). In
January 1969
STEROID-INDUCED ULCERS IN THE RA T
27
FIG. 3. Effect of late pregnancy on steroid-induced ulcers. View of stomach opened along greater curvature. A, control, untreated and nonpregnant. B, prednisolone, nonpregnant. Numerous deep ulcers in the glandular portion. C, prednisolone from days 14 through 17 of pregnancy, animals killed on day 18. Complete prevention of ulcers. TABLE
1. Effect of pseudopregnancy on steroidinduced ulcers· I
III
II
ConControl trol vehicle prednisolone
+
+
IV PseuPregdopregnant nant + I.'redprednisolone mso)one
+
No. of animals .. . .
6
15
21
--17
Ulcers Incidence (% ). Severity (0 to
0
73
76
35
-- - ---
3+) .....
No. per stomach Ulcer index. Change from group II (%).
0
-
--
0.7 2.7
0.7 2.3
0.3 l.1
10.7
10.6
4.9
-1
-54
• Prednisolone (25 mg per kg) started on day 6 of either pseudopregnancy or pregnancy and administered for 4 days.
the case of steroid-induced ulcers, the respective role of the fetus and the placenta was not determined; their presence, however, does not seem necessary, since ulcers were prevented during the first 4 days of pregnancy (that is, before implantation of the blastocyst) as well as during prolonged lactation (that is, after fetus and placenta had been expulsed) . The mechanism by which pregnancy and lactation protect against ulcer formation is unknown. Ovarian hormones may contribute to the antiulcer effect of pregnancy, as suggested by the observation that the preponderance of peptic ulcer in men holds true only during the child bearing age (e.g., when secretion of ovarian hormones is highest) . Before puberty, the incidence is about the same in both sexes and with the onset
KELLY AND ROBERT
28 GRAMS/DAY
50
40
FOOD INTAKE PARTURITION
MATING
1
1
30
t
r~
J.t i
20 /
CONTROLS
10
FLUID INTAKE
MLlOAY
100 MATING
80
1
60
/
CONTROLS
20
o'---5=---!-o----!,--,--~0-~15---;::20~---;2;;-5-~30 DAYS
FIG. 4. Food and water intake during pregnancy and lactation. During pregnancy, from days 0 through 3 for food, and from days 0 through 5 for water, values between both groups are not statistically different. Beyond these days, the difference be· tween both groups are statistically different (P < 0.01), except on day 2 postpartum.
of menopause the incidence in females increases sharply. 1. 3 Fajer and BarracloughS reported that progesterone secretion during pregnancy in the rat reaches a peak on days 13 to 15, and it is at that time (days 14 to 18) that steroid ulcer inhibition was highest (fig. 1). The fact, however, that pseudopregnancy did not reduce steroid ulcer formation in the rat does not support an antiulcer effect mediated by ovarian hormones. Pregnancy may alter gastric secretion in such a way that corticoids cannot induce ulcers easily anymore. However, Lilja and Svensson 9 found a sharp increase in acid secretion during pregnancy and lactation in the rat, both basal and stimulated with histamine or gastrin, from the first week of pregnancy onward,
Vol. 56, No . 1
with a peak in the third week. Therefore, the antiulcer effect of pregnancy in the rat cannot be ascribed to a reduction in acid secretion. In previous studies 4 • 5 on steroid-induced ulcers, the animals were fasted during treatment with prednisolone, whereas in the present experiments they were fed throughout. This change in technique was made because it was feared that fasting for 4 days, in addition to prednisolone administration, might interfere with pregnancy. As a consequence, the ulcers were not so severe as in fasted rats; however, at autopsy the fetuses, removed while the mothers were still breathing, were alive, and the ad libitum feeding permitted us to correlate the amount of daily food intake with ulcer formation. Food intake was increased from the third day of pregnancy and during lactation (fig. 4) . The increased food in the stomach could have acted as a buffer to gastric secretion and thereby prevented erosion of the mucosa. It is unlikely, however, that this factor played a significant role, because the degree of ulcer inhibition was the same (50%) during the first 4 days of pregnancy, at which time food and water intake were not increased significantly, as during the midportion of pregnancy, when the intake was increased. Moreover, if the increase in food and water intake had played a major part in preventing ulcer formation , the greatest protection should have taken place during lactation (which was not the case), since at that time the animals were ingesting up to 2.5 times as much food and water as the controls. Food and water intake was not measured during pseudopregnancy. REFERENCES 1. Sandweiss, D. J. , H. C. Saltztein, and A. A. Farbman. 1939. The relation of sex hormones to peptic ulcer. Amer. J. Dig. Dis. 6: 6-12. 2. Bockus, H. L. 1963. Gastroenterology, Ed. 2, Vol. 1, p. 467. W. B. Saunders Company, Philadelphia. 3. Clark, D. H. 1953. Peptic ulcer in women. Brit. Med . J. 1: 1254-1257. 4. Robert, A., and J. E. Nezamis. 1958. Ulcerogenic
January 1969
STEROID-INDUCED ULCERS IN THE RA T
property of steroids. Proc . Soc. Exp. Biol. Med. 99: 443-447. 5. Robert, A., and J . E . Nezamis. 1964. Histopathology of steroid-induced ulcers. Arch. Path. (Chicago) 77: 407-423. 6. Staples, R. E. 1965. Induction of pseudopregnancy in the rat by vaginal stimulation at various stages of the estrous cycle. Anat. Rec. 152: 499-502. 7. Kahlson, G. , B. Lilja, and S. E. Svensson. 1964.
29
Physiological protection against gastric ulceration during pregnancy and lactation in the rat. Lancet 2: 1269-1272. 8. Fajer, A. B., and C. A. Barraclough . 1967. Ovarian secretion of progesterone and ",-hydroxypregn4-en-3-one during pseudopregnancy and pregnancy in rats. Endocrinology 81: 617-622. 9. Lilja, B., and S. E. Svensson. 1967. Gastric secretion during pregnancy and lactation in the rat. J. Physiol. (London) 190: 261-272.