somatostatin stimulates prostaglandin production by rat gastric epithelial cellsin vitro, but is not...

Digestive Diseases and Sciences, Vol. 33, No. 11 (November 1988), pp. 1435-1440

Somatostatin Stimulates Prostaglandin Production by Rat Gastric Epithelial Cells

in Vitro, but Is Not Cytoprotective MARCO ROMANO, MD, MAHNAZ RAZANDI, MS, and KEVIN J. IVEY, MD

Whether somatostatin stimulates prostaglandin synthesis by gastric cells is controversial. Also, it is unknown whether somatostatin protects gastric cells against exogenous injury in conditions independent o f systemic factors and of inhibition of gastric acid secretion. The present study was undertaken (1) to evaluate the effect o f somatostatin on prostaglandin production by rat gastric epithelial cells in monolayer culture and (2) to assess whether somatostatin protects gastric cells against taurocholate- and indomethacin- induced damage in vitro. Somatostatin at concentrations o f 10 -5 M and 10 -4 M significantly stimulated PGE2 and 6-keto-PGFj, production by rat gastric epithelial cells but was not able to prevent damage induced by sodium taurocholate and indomethacin to rat gastric cells in monolayer culture. These results suggest that: (1) somatostatin stimulates prostaglandin synthesis by cultured rat gastric epithelial cells, but (2) is not directly protective to rat gastric epithelial cell monolayers against drug-induced damage in vitro.

KEY WORDS: somatostatin; prostaglandin E2; prostacyclin; cytoprotection; taurocholate; indomethacin.

Somatostatin (SS) is a potent inhibitor of gastric acid secretion in several species (1-3). Whether this effect is partially mediated by prostaglandin E2 (PGE2), which is an inhibitor of gastric secretion (4, 5), is controversial (6-9). Prostacyclin (PGI2) also inhibits gastric secretion (5, 10). The effect of somatostatin on production of 6-keto-prostaglandin

Manuscript received August 12, 1987; revised manuscript received February 26, 1988; accepted March 10, 1988.

From the Veterans Administration Medical Center Long Beach, California; and University of California, Irvine, Califor- nia.

This work was supported by the Medical Research Service of the Veterans Administration.

Dr. Romano is a visiting scientist from the Istituto di Medicina Generale e Metodologia Clinica, 1st School of Medicine, Uni- versity of Naples, Italy.

Address for reprint requests: Dr. Kevin J. Ivey, 151 Medical Research, VA Medical Center, 5901 E. 7 Street, Long Beach, California 90822.

F~ (6-keto-PGFl~, the stable metabolite of PGIz) by gastric cells has not been evaluated.

Somatostatin has been reported to be antiulcerogenic (11, 12). Further, somatostatin protects rat gastric mucosa against stress-related damage (13) and prevents hemorrhagic gastric erosions induced by ethanol in rats in vivo (14). The mechanism of the protection by somatostatin is not clear. In particular it is unclear (1) if it is due to the peptide's antisecretory effect, (2) if vascular or systemic factors are needed for this protection to occur, or (3) if it is partially contributed to by a direct effect on gastric cells. Furthermore, it is unknown whether somatostatin can provide protection against damage induced by sodium taurocholate (NAT) or indomethacin (Ind).

Aims of the present study were: (1) to evaluate the effect of somatostatin on PGEz and 6-keto-

Digestive Diseases and Sciences, Vol. 33, No. 11 (November 1988) 0163-2116./88/1100-1435506.00/0 �9 1988 Plenum Publishing Corporation

1435

PGFI~ production by rat gastric epithelial cells in vitro, and (2) to evaluate the effect of somatostatin on damage induced by sodium taurocholate and indomethacin to rat gastric epithelial cell monolayers (a preparation which completely excludes the influence of vascular and systemic factors). As our model is predominantly constituted of mucus-producing cells (15), the antisecretory effect of somatostatin in any protection is also excluded.

MATERIALS AND METHODS

Materials. The animals used in the present study were 7- to 9-day-old rats (Sprague-Dawley, Charles River, Wilmington, Massachusetts). Medium I consisted of Coon's modified Ham's F-12 medium (KC Biological Inc., Lenexa, Kansas) containing 0.1% collagenase (120 units/mg, GIBCO, Grand Island, New York) and 0.05% hyaluronidase (type I-S, 270 units/mg, Sigma Chemical Co., St. Louis, Missouri), 100 unit/ml penicillin, 100 Ixg/ml streptomycin, and 25 i~g/ml fungizone. These antibiotics and the antimycotic were purchased from Irvine Scientific Co., Santa Ana, California. Medium II consisted of F-12 medium supplemented with heat-inacti- vated (at 57~ for 30 min) 10% fetal bovine serum (GIBCO), 15 mM HEPES buffer (Sigma), fibronectin 2 ixg/ml (Sigma), and 1% antibiotic-antimycotic solution described above. Sodium taurocholate, indomethacin, and somatostatin were purchased from Sigma. Sodium taurocholate and somatostatin were dissolved in F-12 medium and used immediately. A stock solution of indomethacin 25 mM was obtained by dissolving the drug in Na2CO3 0.2 M; pH was adjusted to 7.4 by adding NaH2- PO4 5 M. Desired concentration (2.5 mM) was obtained by diluting stock solution with F-12 medium. Chromium 51 (sodium chromate 200-900 Ci/g chromium) was purchased from ICN Biomedicals, Irvine, California. [125I]Prostaglandin E2 and 6-keto-prostaglandin F~ were purchased from New England Nuclear, Boston, Massa- chusetts.

Cell Culture. The method has been described in detail previously (15). In brief, the fundic area was excised from rat stomach and minced into 2- to 3-mm 3 pieces. The minced tissues were gassed with 02 and incubated in medium I at 37 ~ C for 60 min in a shaking water bath. The tissues were then pipetted several times and filtered through a nylon mesh (Nytex, Tetko Inc., Elmsford, New York). The filtrate was washed by centrifugation at 600 rpm for 5 min at 4 ~ C in F-12 medium. The cell pellet was resuspended in medium II and inoculated onto 35 x 10-ram tissue culture plates (Corning Glass, Corning, New York). The cultures were maintained in a Steri-cult incubator (Forma Scientific, Marietta, Ohio) at 37 ~ C in a humidified atmosphere of 5% COz in air. Confluent monolayers (3-day-old cultures) were studied.

Chromium-51 Release Assay. The method for chromium-51 release assay was as described elsewhere (16, 17). The media were discarded and the monolayers were washed three times with 1 ml of F-12 medium (37 ~ C) to remove floating cells. The cells were then incubated in

ROMANO ET AL

F-12 medium containing 5 ixCi/ml of 51Cr for 60 min in the culture condition. The labeled cells were washed five times with F-12 medium to remove excess isotope and then 1 ml of F-12 medium containing test drugs as described under "Experimental Studies" was added to the monolayers. After incubation for the experimental period in the culture condition, medium A was collected and the monolayers were washed with medium B. Media A and B were combined and centrifuged at 2000 rpm for 15 rain at 4 ~ C. The pellets were combined with the corresponding monolayers and dissolved in NaOH 1 N for 24 hr. 51Cr radioactivity of the cells and of the supernatants was counted with an automatic gamma counter (Beckman 7000, Beckman Instruments Inc., Ful- lerton, California). The percentage of 51Cr released per sample was expressed as:

Release (%) = cpm supernatant x 100 cpm supernatant + cpm cells

or as specific 51Cr release (%) (ie, release caused by drug action) = release (%) in the presence of test drug - spontaneous release (%) (ie, 51Cr release from control monolayers incubated with medium only). In 51Cr release assay experiments, F-12 medium was not supplemented with fetal bovine serum and was free of antibiotics and antimycotics.

Prostaglandin Assay. To measure production of PGE2 and 6-keto-PGF~ (the stable metabolite of PGI2) by cultured cells, the culture medium was aspirated and the monolayers were rinsed three times with 1 ml of F-12 medium. After rinsing, F-12 medium alone or with somatostatin at the concentration indicated under "Experimen- tal Studies" was layered on each monolayer. The monolayers were then incubated for 60 min. The medium was collected and centrifuged for 5 min at 2000 rpm and 4 ~ C. The supernatant was collected, gassed with N2, and stored at -70~ until assayed. The pellets were combined with corresponding monolayers and protein was determined with the dye-binding test according to Brad- ford (18). PGE2 and 6-keto-PGFl~ were measured directly in duplicate with highly sensitive 1251 radioimmunoassay kits. Standards in the range of 0.2-50 pg/0.1 ml PGE2 and 2.0-50 pg/0.1 ml 6-keto-PGFl~ were treated in the same way as the samples and the curve calculated on semilog- arithmic paper after counting in a Beckman 7000 gamma counter. The limits of detection were 0.2 pg PGE2 and 2.0 pg 6-keto-PGFl~ in 0.1 ml volume per assay tube. For PGE2, cross-reactivity with prostaglandin E1 was 3.7% and with all other prostaglandins less than 0.4%. For 6-keto-PGFl~, cross-reactivity with prostaglandin F2~ was 2.6% and with all other prostaglandins less than 2%. Cross-reactivity between drugs and antisera to prostaglandins was evaluated in each assay experiment. In prostaglandin assay experiments, F-12 medium was used (ie, medium not supplemented with fetal bovine serum and antibiotic- and antimycotic-free).

Experimental Studies. To study the effect of somatostatin on prostaglandin production by cultured cells, monolayers were incubated with medium containing 10-8_10 4 M somatostatin or medium only (control) for 60 min. Cell-free supernatant was collected and assayed for PGE2 and 6-keto-PGFl~.

1436 Digestive Diseases and Sciences, Vol. 33, No. 11 (November 1988)

SOMATOSTATIN AND PROSTAGLANDIN PRODUCTION IN VITRO

20

. c

c �9 ~ 15

0 =. o.

E

g 5 o O.

* * p = : 0 . 0 1 v s C o n t r o l * * * p ~ 0 . 0 0 1 v s C o n t r o l

C o n t r o l 8

I

~ n=~

7 6 5

n=8

-,oQ Essl. M

Fig 1. Effect of somatostatin (SS) on PGEz production by cultured cells. Mean -+ SE of n cultures.

To study the effect of somatostatin on indomethacin- induced inhibition of prostaglandin production, monolayers were incubated with indomethacin 10 -4 M for 15 min, washed, and incubated with indomethacin 10 -4 M with and without somatostatin 10 -4 M for 60 min. Cell-free supernatant was then collected and PGE2 and 6-keto- PGFt~ determined.

To study the effect of somatostatin on taurocholate- induced damage, monolayers were incubated with somatostatin 10-6-10 -4 M or medium only (control) for 60 min. After 60 min of incubation, sodium taurocholate was added to reach the final concentration of 10 mM, and cells were incubated for 30 min more.

To study the effect of somatostatin on indomethacin- induced damage, monolayers were incubated with somatostatin 10-6-10 -4 M or medium only (control) for 60 min. After 60 min of incubation with somatostatin alone, indomethacin was added to reach the final concentration of 2.5 mM, and cells were incubated for 180 min more.

Statistical Analysis. Data are expressed as mean +-- standard error (SE). Significance was assessed by analysis of variance and, when the F value was significant, by Duncan's new multiple-range test (19). Differences were considered significant if P was <0.05.

RESULTS

Tissue Culture. Cells were initially plated in isolated clumps and then spread out to form a confluent monolayer of polygonal-shaped cells. More than 90% of the cultured cells were identified as mucus- producing cells by periodic acid-Schiff staining and ultrastructural studies (15).

Effect of Somatostatin on Prostaglandin Ez Produc- tion by Cultured Cells. Cultured cells produced PGE2 in the amount of 7.8 -+ 0.8 ng/mg protein/hr (Figure 1). Somatosta t in 10 -5 M and 10 -4 M increased PGEe product ion to 13.3 -+ 1.0 ng/mg

"d .c .-.E 4 * * p - : : 0 . 0 1 vs C o n t r o l

* * * p ~ 0 . 0 0 1 v s C o n t r o l * * *

o. 3

E

o a. 1 O

co C o n t r o l 8 7 6 5 4

I i -,oQ [SS~.M

Fig 2. Effect of somatostatin (SS) on 6-keto-PGFl,~ production by cultured cells. Mean -+ SE of n cultures.

protein/hr (P < 0.01 vs control) and to 15.7 --- 2.0 ng/mg protein/hr (P < 0.001 vs control), respectively (Figure 1).

Effect of Somatostatin on 6-Keto-Prostaglandin FI~ Production by Cultured Cells. Cultured cells produced 6-keto-PGFl~ in the amount of 1.3 --- 0.1 ng/mg protein/hr (Figure 2). Somatos ta t in 10 -5 M and 10 -4 M increased 6 - k e t o - P G F ~ product ion to 2.5 - 0.2 ng/mg protein/hr (P < 0.01 vs control) and to 3.1 - 0.4 ng/mg protein/hr (P < 0.001 vs control), respect ively (Figure 2).

Effect of Somatostatin on Indomethacin-Induced Inhibition of Prostaglandin Synthesis. Table 1 shows that indomethacin 10 - 4 M almost comple te ly sup- pressed PGE2 and 6-keto-PGFl~ synthesis by cultured cells. Somatosta t in 10 - 4 M did not p revent the inhibition of prostaglandin synthesis due to indomethacin.

Effect of Somatostatin on Taurocholate-Induced Damage to Cultured Cells. Somatos ta t in by itself did not cause cell damage as assessed quanti tat ively by 5~Cr release assay (Figure 3). Somatos ta t in 10 -6 - 10 -4 M did not afford significant protec t ion against

TABLE 1. Effect of Somatostatin (SS) on Indomethacin (Ind)-Induced Inhibition of Prostaglandin Production by

Cultured Cells (Mean -+ SE of 6 CULTURES) PGE2 6-keto-PGFl~

(ng/mg protein/hr) (ng/mg protein/hr)

Control 7.1 -+ 1.4 1.3 -+ 0.3 Ind l0 4 M 0.4 -+ 0.1* 0.2 -+ 0.1* Ind l0 -4 M + 0.8 -+ 0.1* 0.3 -+ 0.1*

SS 10 4 M ns t n s t

*P < 0.001 vs control. tns: not significant vs Ind 10 -4 M.

Digestive Diseases and Sciences, Vol. 33, No. 11 (November 1988) 1437

ROMANO ET AL

50

40 v @ to

a0

~3 g 2o .2

~ 10- o.

n = 5

n = 8 i--3s

Control SS

n 8 =

n . s .

[ vs I NaT 10raM

= = n = 8 n = 8 n = 8

NaT SS SS SS SS SS 10-4M tOmM tO-6M 5x10-6M 10-5M 5x10-SM 10-4M

+ + + + +

NaT NaT NaT NaT NaT l O m M lOmM 10mM 10mM lOmM

Fig 3. Effect of somatos ta t in (SS) on sodium taurocholate (NAT) - induced damage to rat gastric epithelial cells in t issue culture. Mean -+ SE o f n cul tures; n.s. : not statistically significant vs NaT 10 mM.

damage brought about by sodium taurocholate 10 mM (Figure 3).

Effect o f S o m a t o s t a t i n on I n d o m e t h a c i n - I n d u c e d D a m a g e to Cultured Cells. Figure 4 shows that somatostatin over the range of concentration used did not protect cultured cells against damage induced by indomethacin 2.5 mM.

DISCUSSION

The present study demonstrates that somatostatin significantly stimulates PGEz and 6-keto- PGF]~ production by cultured rat gastric epithelial cells. Somatostatin, at concentrations which stimulate prostaglandin production, does not exert any protective effect against damage induced by sodium

50

4 0

t~

3 0 - 0:

~3 ~' 20 o

o | o. 1 0

I n=5

n=8

Control SS Ind SS

n.s, vs

Ind 2.5 mM i

SS SS SS SS 10-4M 2.5mM 10-6M 5x10-6M 10-5M 5x10-SM 10-4M

+ + + + + Ind Ind Ind Ind Ind

2,5ram 2.5rnM 2,SmM 2,5rnM 2,5 rnM

Fig 4. Effect of somatos ta t in (SS) on indomethacin (Ind) - induced damage to rat gastric epithelial cell monolayers . Mean - SE of n cul tures; n.s . : not statistically significant vs Ind 2.5 mM.

taurocholate and indomethacin. The increase in prostaglandin synthesis induced by somatostatin is not enough to reach the minimum dose of prostaglandin E2 which, exogenously administered, is able to protect rat gastric cells against taurocholate- induced damage.

Somatostatin has antiulcerogenic effects (11, 12) and protects rat gastric mucosa in vivo against ethanol- and stress-induced damage (13, 14). The protective effect of somatostatin has been attributed to its antisecretory effect and to stimulation of gastric mucus production (20). Furthermore, Szabo and Usadel have hypothesized that protection by somatostatin is related to the peptide's sulfhydryl groups and that vascular endothelium of the stomach is the target site (14). We evaluated whether somatostatin is directly protective to gastric cells in tissue culture, an experimental model which completely excludes the influence of vascular as well as systemic factors. As our model is predominantly constituted of mucous cells, the acid-inhibitory effect of somatostatin in any protection is negligible. In these experimental conditions, somatostatin did not protect against damage induced by an agent which interferes with prostaglandin synthesis (indomethacin) and one which does not (taurocholate) (21). This is not surprising, since we have previously reported (17) that the lowest concentration of exogenously administered 16,16-dimethyl-PGE2 able to protect rat gastric cells against taurocholate- induced injury is 0.01 IxM.

The concentration of PGE2 in the medium after 1 hr incubation with somatostatin 10 -4 M in the present study is 0.005 ~zM, considerably lower than the minimum amount of the more potent 16,16- dimethyl-PGE2 necessary to protect cells against exogenous injury (17). Furthermore, arachidonic acid, in a concentration that stimulates PGE2 production in a similar manner to somatostatin, does not protect cultured rat gastric mucosal cells against taurocholate-induced damage (22). These findings indicate that somatostatin does not stimulate prostaglandin synthesis by gastric mucous cells suffi- ciently to protect these cells. It is possible that while mucous cells are unable to synthesize enough prostaglandin to protect themselves, other gastric cell types might produce sufficient protective prostaglandins in vivo. Recently, Chen et al (23) have reported that macrophages and endothelial cells are the major source of prostaglandins in canine fundic gastric mucosa. Alternatively, it can be speculated that the protection of gastric mucosa afforded by


S O M A T O S T A T I N A N D P R O S T A G L A N D I N P R O D U C T I O N I N V I T R O

somatostatin in vivo is mediated by vascular factors and by inhibition of gastric acid secretion and is not due to a significant direct effect on gastric cells.

The effect of somatostatin on prostaglandin production by gastric mucosa is still controversial (6-8). Ligumski et al demonstrated that somatostatin potentiates carbamylcholine-induced synthesis of PGE2 from isolated perfused rat stomach and that the ability of somatostatin to inhibit acid secretion was blocked by the prostaglandin synthesis inhibitor indomethacin (6). On the other hand, Mogard et al have shown that prostaglandin synthesis inhibition by indomethacin does not affect somatostatin-induced inhibition of bethanechol-stimulated acid secretion in rats (8). Furthermore, Mogard et al have demonstrated that somatostatin does not stimulate PGEz release from the isolated perfused rat stomach nor does it increase the amount of PGEz released by carbamylcholine (24). The doses of somatostatin used in this study were 10-~~ -8 M, and the authors did not exclude the possibility that higher concentrations of the peptide could stimulate gastric PGE2 release. In our in vitro experimental model (monolayers of rat gastric epithelial cells), we found that somatostatin 10 -5 M and 10 -4 M increased by 70% (P < 0.01) and 100% (P < 0.001), respectively, the PGE2 production by cultured cells. However, somatostatin was not able to prevent the inhibition of prostaglandin synthesis induced by indomethacin. The different experimental model and the higher concentration of the peptide may account for the difference between our results and those of Mogard et al (24). We did not, however, find any increase in PGE2 production with the higher concentration of somatostatin (!0 -8 M) used by Mogard et al (24). Our study also shows that somatostatin significantly increases the amount of 6-keto-PGFl~ (the metabolite of PGI2) produced by rat gastric cells.

We have previously shown that prostaglandin, cimetidine, and omeprazole, which are inhibitors of gastric acid secretion, are also cytoprotective in vitro, in conditions independent of their antisecretory effect (17, 25, 26). No stimulation of endogenous prostaglandin synthesis by these agents was found, however. Somatostatin, therefore, differs from these antisecretory agents in as much as it is not cytoprotective in vitro but does stimulate prostaglandin production. The amount of prostaglandin produced by mucous cells however, is insufficient to cause protection.

In conclusion, these results suggest that somato-

statin (i) stimulates prostaglandin production by rat gastric epithelial cells grown in tissue culture, but (2) is not directly protective against drug-induced damage to rat gastric mucosal cells in vitro, in conditions independent of systemic factors and of inhibition of gastric acid secretion.

REFERENCES

1. Bloom SR, Mortimer CH, Thorner MO, Besser GM, Hall R, Gomez-Pan R, Roy VM, Russel RCG, Coy DH, Kastin AJ, Schally AV: Inhibition of gastrin and gastric acid secretion by growth hormone release-inhibiting hormone. Lancet 2: 1106-1109, 1974

2. Konturek S J, Tasler J, Cjeszkowski M, Coy DH, Schally AV: Effect of growth hormone release-inhibiting hormone on gastric secretion, mucosal blood flow, and serum gastrin. Gastroenterology 70:737-741, 1976

3. Creutzfeldt W, Arnold R: Somatostatin and the stomach: Exocrine and endocrine aspects. Metabolism 27(Suppl 1): 1309-1315, 1978

4. Robert A, Nezamis JE, Phillips JR: Inhibition of gastric secretion by prostaglandins. Am J Dig Dis 12:1973-1976, 1967

5. Soil AH: Specific inhibition by prostaglandin Ez and Iz of histamine stimulated [14C]aminopyrine accumulation and cyclic adenosine monophosphate generation by isolated canine parietal cells. J Clin Invest 65:1222-1229, 1980

6. Ligumski M, Goto Y, Debas H, Yamada T: Prostaglandins mediate inhibition of gastric acid secretion by somatostatin in the rat. Science 219:301-303, 1983

7. Alino SF, Marti-Bonmati E, Torregrosa A, Callaghan R, Morcillo E, Garcia D, Gallego J, Esplugues J: Prostaglandin synthesis inhibition reverses the gastric antisecretory activ- ity of somatostatin in anaesthetized rats. Horm Metab Res 17:123-126. 1985

8. Mogard MH. Kauffman GL Jr. Pehlevanian M. Golanska E. Elashoff JD. Walsh JH: Prostaglandins may not mediate inhibition of gastric acid secretion by somatostatin in the rat. Regul Peptides 10:231-236. 1985

9. Mogard MH. Maxwell V. Kovacs T. Van Deventer G. Elashoff JD. Yamada T. Kauffman GL Jr. Walsh JH: Soma- tostatin inhibits gastric acid secretion after gastric mucosal prostaglandin synthesis inhibition by indomethacin in man. Gut 26:1189-1191. 1985

10. Konturek SJ. Robert A. Hanchar AJ. Nezamis JE: Compar- ison of prostacyclin and prostaglandin E2 on gastric secretion. gastrin release, and mucosal blood flow in dogs. Dig Dis Sci 25:673-679. 1980

11. Mattes P. Raptis S. Heil Th. Rasche H. Scheck R: Extended somatostatin treatment of a patient with bleeding ulcer. Horm Metab Res 7:508-511. 1975

12. Kayasseh L. Gyr K. Keller U. Stalder GA. Wall M: Soma- tostatin and cimetidine in peptic-ulcer haemorrhage. A ran- domized controlled trial. Lancet 1:844-846. 1980

13 Zierend E. Hengst K. Wagner H. Gerlak M: Inhibition of stress ulcer formation with somatostatin in rats. Res Exp Med 168:199-204. 1976

14. Szaho S. Usadel KH: Cytoprotection-organoprotection by somatostatin: Gastric and hepatic lesions. Experientia 38: 254-256. 1982

Digestive Diseases" and Sciences, Vol. 33, No. 11 (November 1988) 1439

ROMAN0 ET AL

15. Terano A, Ivey KJ, Stachura J, Sekhon S, Hosojima H, McKenzie WN Jr, Krause W J, Wyche JH: Cell culture of rat gastric fundic muCosa. Gastroenterology 83:1280-1291, 1982

16. Wigzell H: Quantitative titrations of mouse H-2 antibodies using 51Cr labelled target cells. Transplantation 3:423-431, 1975

17. Terano A, Ota S, Mach T, Hiraishi H, Stachura J, Tarnawski A, Ivey KJ: Prostagiandin protects against taurocholate- induced damage to rat gastric mucosal cell culture. Gastro- enterology 92:669-677, 1987

18. Bradford MM: A rapid and sensitive method for the quanti- tation of microgram quantities of protein utilizing the prin- ciple of protein-dye binding. Anal Biochem 72:248-254, 1976

19. Duncan DB: Multiple range and multiple F tests. Biometrics i1:1-42, 1955

20. Johansson C, Aly A: Stimulation of gastric mucus output by somatostatln in man. Eur J Clin Invest 12:37-39, 1982

21. Konturek SJ, Brzozowski T, Radecki T, Dobrzanska M: Generation of endogenous prostaglandins and thromboxanes in taurocholate-induced gastric mucosal lesions. Scand J Gastroenterol 19:91-96, 1984

22. ota s, Razandi M, Terano A, Hiraishi H, Ivey KJ: Arachi- donic acid does not protect against sodium taurocholate damage to rat gastric epithelial cell cultures. Gastroenterol Jpn 22:285-291, 1987

23. Chen M, Sanders M, Thomas L, Amirian D, Kauffman G, S0il AH: Prostaglandin production in canine fundic gastric mucosa: Identification of major cell sources. Gastroenterol- ogy 90:1361, 1986(abstract)

24. Mogard MH, Kauffman GL Jr, Pehlevanian M, Reddy TJ, Elashoff JD, Walsh JH: Carbamylcholine, but not somatostatin or neurotensin, stimulates prostaglandin E2 release from the isolated perfused rat stomach. Regul Peptides i5:71-76, 1986

25. Terano A, Mach T, Stachura J, Tarnawski A, Ivey KJ: Effect of 16,16-dimethyl prostaglandin E2 on aspirin induced damage to rat gastric epithelial cells in tissue culture. Gut 25:19-25, 1984

26. Romano M, Razandi M, Ivey KJ: Cimetidine and omeprazole directly protect human gastric epithelial cells in

vitro. Gastroenterology 92:1599, 1987(abstract)


somatostatin stimulates prostaglandin production by rat gastric epithelial cellsin vitro, but is not...

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