Prostaglandin E(2)-activated housekeeping Cl(-) channels in the basolateral membrane of rat gastric parietal cells

Gastroprotective potential of hydro-alcoholic extract of Pattanga (Caesalpinia sappan Linn.)

ETHNO-PHARMACOLOGICAL RELEVANCE

Pattanga is botanically equated as Caesalpinia sappan Linn. (Family: Caesalpiniaceae) and is used in Ayurveda system of medicine since ages. According to Ayurveda, useful part is Heartwood, which is bitter, astringent and acrid and is useful in vitiated conditions of vata and pitta, burning sensation, wounds, ulcers, leprosy, skin diseases, menorrhagia, leucorrhea, and diabetes. It is used as a major ingredient in Ayurvedic formulations and preparations like Patrangasava, Chandanadya Thalia, and Karpuradyarka.

AIM OF THE STUDY

The present study is planned to evaluate the gastroprotective activity of the selected Ayurvedic drug using three different in vivo gastric ulcer models, so as to provide scientific evidence for the Ayurvedic claims.

MATERIALS AND METHODS

For this study, Wistar albino rats fasted overnight were selected. The hydroalcoholic extract of Caesalpinia sappan heartwood at the dose level 250 and 500mg/kg body weight was selected and administered orally before necrotizing agents. Antioxidant and antiulcer parameters were evaluated and the stomach samples were subjected for histopathological studies. In addition, PGE2 estimation and protein expressions of COX-1, COX-2 and iNOS were analyzed by Western blot. The plant extract was subjected to LCMS/MS analysis. In addition, Cytoprotective effect in isolated gastric mucosal cells, TUNEL Assay, Acid neutralizing capacity assay, H⁺/K⁺ ATPase inhibitory assay were performed.

RESULTS

The ulcer protection was found to be 92%, 86% and 64% against ethanol, NSAID and pylorus ligation induced ulcer respectively. The hydro-alcoholic extract of C. sappan heartwood exhibited cytoprotective effect with 76.82% reduction against indomethacin-induced cytotoxicity at the concentration of 25µg/ml. C. sappan showed 63.91% inhibition in H⁺/K⁺ ATPase inhibitory assay at the concentration 500µg/ml.

CONCLUSIONS

Our results depict that Caesalpinia sappan heartwood possesses gastroprotective activity, possibly mediated through cytoprotection and antioxidant mechanisms. The data obtained in the present study provides scientific support for the traditional use of Caesalpinia sappan in the management of peptic ulcer.

Serotonin and histamine mediate gastroprotective effect of fluoxetine against experimentally-induced ulcers in rats

Research in the treatment of gastric ulcer has involved the investigation of new alternatives, such as anti-depressant drugs. The present study was designed to investigate the gastroprotective effects of fluoxetine against indomethacin and alcohol induced gastric ulcers in rats and the potential mechanisms of that effect. Fluoxetine (20 mg/kg) was administered IP for 14 days. For comparative purposes, other rats were treated with ranitidine (30 mg/kg). Thereafter, after 24 h of fasting, INDO (100 mg/kg) or absolute alcohol (5 ml/kg) was administered to all rats (saline was administered to naïve controls) and rats in each group were sacrificed 5 h (for INDO rats) or 1 h (for alcohol rats) later. Macroscopic examination revealed that both fluoxetine and ranitidine decreased ulcer scores in variable ratios, which was supported by microscopic histopathological examination. Biochemical analysis of fluoxetine- or ranitidine-pre-treated host tissues demonstrated reductions in tumor necrosis factor (TNF)-α and myeloperoxidase (MPO) levels and concomitant increases in gastric pH, nitric oxide (NO) and reduced glutathione (GSH) contents. Fluoxetine, more than ranitidine, also resulted in serotonin and histamine levels nearest to control values. Moreover, immuno-histochemical analysis showed that fluoxetine markedly enhanced expression of cyclo-oxygenases COX-1 and COX-2 in both models; in comparison, ranitidine did not affect COX-1 expression in either ulcer model but caused moderate increases in COX-2 expression in INDO-induced hosts and high expression in alcohol-induced hosts. The results here indicated fluoxetine exhibited better gastroprotective effects than ranitidine and this could be due to anti-secretory, anti-oxidant, anti-inflammatory and anti-histaminic effects of the drug, as well as a stabilization of gastric serotonin levels.

Efficacy and safety of parecoxib/phloroglucinol combination therapy versus parecoxib monotherapy for acute renal colic: a randomized, double-blind clinical trial

To investigate whether the addition of phloroglucinol to parecoxib could improve the efficacy in patients with acute renal colic. Patients of acute renal colic were randomly allocated to receive intravenous Parecoxib 40 mg plus placebo or Parecoxib 40 mg plus phloroglucinol 80 mg, respectively. Pain intensity was recorded using a visual analog scale (VAS) before drug administration and 5, 15, 30, 60, and 120 min after treatment start. The primary outcome was the mean pain intensity difference (PID) at each checkpoint and the effectiveness of drugs (≥ 50 % decrease in VAS score at the end checkpoint). The need for rescue analgesics and the incidence of adverse effects were considered as secondary outcome of the study. Among 236 patients enrolled in the study, 119 patients received intravenous parecoxib plus placebo and 114 patients received intravenous parecoxib plus phloroglucinol, the remaining 3 patients given up treatment. Baseline demographics were similar between two groups. There are significant differences in the PID at 15 and 30 min between two groups (P15 min = 0.011, P30 min = 0.013). Rescue analgesics were required by 17 patients (14.3 %) receiving parecoxib, 7 patients (6.1 %) receiving parecoxib plus phloroglucinol (P = 0.041). There were no differences in PID at other checkpoints between two groups, as well as in the incidence of adverse events and the drug effectiveness. Parecoxib in combination with phloroglucinol for acute renal colic has a faster action, also reduces the demand of rescue analgesics.

Ca2+ activated K+ channel Kca3.1 as a determinant of gastric acid secretion

The Ca(2+) activated K(+) channel K(ca)3.1 is expressed in a variety of tissues. In the gastric gland it is expressed in the basolateral cell membrane. To determine the functional significance of K(ca)3.1 activity for gastric acid secretion, gastric acid secretion was determined in isolated glands from gene targeted mice lacking functional K(ca)3.1 (K(ca)3.1(-/-)) and from their wild type littermates (K(ca)3.1(+/+)). According to BCECF-fluorescence cytosolic pH in isolated gastric glands was similar in K(ca)3.1(-/-) and K(ca)3.1(+/+) mice. Na(ca)-independent pH recovery (ΔpH/min) following an ammonium pulse, a measure of H(ca)/K(ca) ATPase activity, was, however, significantly faster in K(ca)3.1(-/-) than in K(ca)3.1(+/+) mice. Accordingly, the luminal pH was significantly lower and the acid content significantly higher in K(ca)3.1(-/-) than in K(ca)3.1(+/+) mice. The abundance of mRNA encoding H(ca)/K(ca) ATPase and KCNQ1 was similar in both genotypes. Increase of extracellular K(ca) concentrations to 35 mM (replacing Na(ca)/NMDG) and treatment with histamine (100 μM) significantly increased ΔpH/min to a larger extent in K(ca)3.1(+/+) than in K(ca)3.1(-/-) mice and dissipated the differences between the genotypes. Carbachol (100 μM) increased ΔpH/min in both genotypes but did not abolish the difference between K(ca)3.1(-/-) and K(ca)3.1(+/+) mice. In K(ca)3.1(+/+) mice the K(ca)3.1 opener DCEBIO (100 μM) did not significantly alter basal ΔpH/min but significantly blunted ΔpH/min in the presence of carbachol. In conclusion, K(ca)3.1 activity suppresses carbachol stimulated gastric acid secretion.

Nitric oxide involved in the IL-1β-induced inhibition of fructose intestinal transport

Interleukin-1β (IL-1β) is a pleiotropic cytokine produced by cells of the immune system and a large variety of other cell types including endothelial cells. It is released during inflammatory and infectious diseases, and possesses a wide spectrum of autocrine, paracrine and endocrine activities. The aim of this work was to examine the IL-1β effect on D-fructose transport across rabbit jejunum and try to identify the mediators implicated in this process. A sepsis condition was induced for 90 min after intravenous (iv) administration of IL-1β and body temperature was recorded. Studies on cellular intestinal integrity have not shown modifications of the epithelium and the basement membrane. D-fructose intestinal transport was studied in rabbit jejunum from control and treated animals and it was reduced in the latter ones. This cytokine decreased both the mucosal to serosal transepithelial flux and the transport across brush-border membrane vesicles of D-fructose. The inhibition was reversed by L-NAME (nitric oxide [NO] synthase inhibitor), but not by indomethacin (cyclooxygenase 1 and 2 inhibitor). Both inhibitors were administered iv 15 min before the IL-1β. The protein levels of GLUT5 were not changed in all animal groups and those of mRNA were even increased. In summary, these findings indicate that IL-1β, at the time assayed, induced a significant reduction in the relative intrinsic activity of GLUT5 and in this decrease are involved NO signalling pathways. In this way, blockage of D-fructose intestinal uptake by IL-1β may be playing an essential role in the pathophysiology of septic shock.

Roles of COX inhibition in pathogenesis of NSAID-induced small intestinal damage

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin decrease mucosal PGE(2) content by inhibiting cyclooxygenase (COX) activity and produce damage in the small intestine. The development of intestinal lesions induced by indomethacin was accompanied by increases in intestinal motility, enterobacterial invasion, and myeloperoxidase (MPO) as well as inducible nitric oxide synthase (iNOS) activity, together with the up-regulation of COX-2 and iNOS mRNA expression. Neither SC-560, a selective COX-1 inhibitor, nor rofecoxib, a selective COX-2 inhibitor, alone caused intestinal damage, but their combined administration provoked lesions in the small intestine. SC-560, but not rofecoxib, caused intestinal hypermotility, bacterial invasion and the expression of COX-2 as well as iNOS mRNA, yet the iNOS and MPO activity was increased only when rofecoxib was administered together with SC-560. Although SC-560 inhibited PG production, the level of PGE(2) recovered in a rofecoxib-dependent manner. The intestinal hypermotility in response to indomethacin was prevented by both 16,16-dimethyl PGE(2) and atropine but not by ampicillin, yet all these agents inhibited not only the bacterial invasion but also the expression of COX-2 as well as the iNOS activity in the intestinal mucosa following indomethacin treatment, thereby preventing the intestinal damage. These results suggest that inhibition of COX-1, despite causing intestinal hypermotility, bacterial invasion and iNOS expression, up-regulates the expression of COX-2, and the PGE(2) derived from COX-2 counteracts the deleterious events caused by COX-1 inhibition and maintains mucosal integrity. These sequences of events explain why intestinal damage occurs when both COX-1 and COX-2 are inhibited.

Effects of a non-selective COX inhibitor and selective COX-2 inhibitors on contractility of human and porcine ureters in vitro and in vivo

BACKGROUND AND PURPOSE

Anti-inflammatory drugs are used in the treatment of acute renal colic. The aim of this study was to investigate the effects of selective COX-2 inhibitors and the non-selective COX inhibitor diclofenac on contractility of human and porcine ureters in vitro and in vivo, respectively. COX-1 and COX-2 receptors were identified in human ureter and kidney.

EXPERIMENTAL APPROACH

Human ureter samples were used alongside an in vivo pig model with or without partial ureteral obstruction. COX-1 and COX-2 receptors were located in human ureters by immunohistochemistry.

KEY RESULTS

Diclofenac and valdecoxib significantly decreased the amplitude of electrically-stimulated contractions in human ureters in vitro, the maximal effect (Vmax) being 120 and 14%, respectively. Valdecoxib was more potent in proximal specimens of human ureter (EC50=7.3 x 10(-11) M) than in distal specimens (EC50=7.4 x 10(-10) M), and the Vmax was more marked in distal specimens (22.5%) than in proximal specimens (8.0%) in vitro. In the in vivo pig model, parecoxib, when compared to the effect of its solvent, significantly decreased the maximal amplitude of contractions (Amax) in non-obstructed ureters but not in obstructed ureters. Diclofenac had no effect on spontaneous contractions of porcine ureter in vivo. COX-1 and COX-2 receptors were found to be expressed in proximal and distal human ureter and in tubulus epithelia of the kidney.

CONCLUSIONS AND IMPLICATIONS

Selective COX-2 inhibitors decrease the contractility of non-obstructed, but not obstructed, ureters of the pig in vivo, but have a minimal effect on electrically-induced contractions of human ureters in vitro.

New Insights into Fatty Acid Modulation of Pancreatic β‐Cell Function

Insulin resistance states as found in type 2 diabetes and obesity are frequently associated with hyperlipidemia. Both stimulatory and detrimental effects of free fatty acids (FFA) on pancreatic beta cells have long been recognized. Acute exposure of the pancreatic beta cell to both high glucose concentrations and saturated FFA results in a substantial increase of insulin release, whereas a chronic exposure results in desensitization and suppression of secretion. Reduction of plasma FFA levels in fasted rats or humans severely impairs glucose-induced insulin release but palmitate can augment insulin release in the presence of nonstimulatory concentrations of glucose. These results imply that changes in physiological plasma levels of FFA are important for regulation of beta-cell function. Although it is widely accepted that fatty acid (FA) metabolism (notably FA synthesis and/or formation of LC-acyl-CoA) is necessary for stimulation of insulin secretion, the key regulatory molecular mechanisms controlling the interplay between glucose and fatty acid metabolism and thus insulin secretion are not well understood but are now described in detail in this review. Indeed the correct control of switching between FA synthesis or oxidation may have critical implications for beta-cell function and integrity both in vivo and in vitro. LC-acyl-CoA (formed from either endogenously synthesized or exogenous FA) controls several aspects of beta-cell function including activation of certain types of PKC, modulation of ion channels, protein acylation, ceramide- and/or NO-mediated apoptosis, and binding to and activating nuclear transcriptional factors. The present review also describes the possible effects of FAs on insulin signaling. We have previously reported that acute exposure of islets to palmitate up-regulates some key components of the intracellular insulin signaling pathway in pancreatic islets. Another aspect considered in this review is the potential source of fatty acids for pancreatic islets in addition to supply in the blood. Lipids can be transferred from leukocytes (macrophages) to pancreatic islets in coculture. This latter process may provide an additional source of FAs that may play a significant role in the regulation of insulin secretion.

Inhibition of small-conductance Cl- channels by the interleukin-1beta-stimulated production of superoxide in rabbit gastric parietal cells

We have shown previously that the G protein-coupled production of superoxide anion (O2-) leads to closure of small-conductance Cl- channels (0.3-0.4 pS) in the basolateral membrane of rabbit parietal cells. In the present study, effects of interleukin-1beta (IL-1beta) on the Cl- channel were investigated. In the whole-cell patch-clamp recording, IL-1beta (0.3-10 ng ml-1) inhibited the whole-cell Cl- current recorded from a parietal cell within isolated rabbit gastric glands. Variance noise analysis of the whole-cell Cl- current showed that the single channel conductance of the Cl- channel that is sensitive to IL-1beta is 0.37 pS. The IL-1beta (1 ng ml-1)-induced decrease of the Cl- current was abolished by anti-IL-1beta antibody (2 microg ml-1), recombinant IL-1 receptor antagonist (500 ng ml-1), GDPbetaS (500 microM) and superoxide dismutase (100 units ml-1), a scavenger of O2-. Northern blot analysis showed that the mRNA of the IL-1 receptor was selectively expressed in rabbit gastric parietal cells. In the dihydrofluorescein diacetate-loaded single parietal cells in gastric glands, IL-1beta (0.3-10 ng ml-1) stimulated the production of oxygen radicals. Y-27632 (1-10 microM), a specific Rho-kinase inhibitor, and fluvastatin (10 microM), an indirect inhibitor for Rho proteins, significantly inhibited the IL-1beta-induced effects on the channel activity and production of oxygen radicals. IL-1beta (0.3-10 ng ml-1) activated Rho in the parietal cells. These results indicate that IL-1beta binds to the IL-1 receptor of gastric parietal cells and inhibits the small-conductance Cl- channel via the G protein-mediated Rho/Rho-kinase-dependent production of O2-.

Prostaglandin E2 protects gastric mucosal cells from apoptosis via EP2 and EP4 receptor activation

Prostaglandin E(2) (PGE(2)) has a strong protective effect on the gastric mucosa in vivo; however, the molecular mechanism of a direct cytoprotective effect of PGE(2) on gastric mucosal cells has yet to be elucidated. Although we reported previously that PGE(2) inhibited gastric irritant-induced apoptotic DNA fragmentation in primary cultures of guinea pig gastric mucosal cells, we show here that PGE(2) inhibits the ethanol-dependent release of cytochrome c from mitochondria. Of the four main subtypes of PGE(2) receptors, we also demonstrated, using subtype-specific agonists, that EP(2) and EP(4) receptors are involved in the PGE(2)-mediated protection of gastric mucosal cells from ethanol-induced apoptosis. Activation of EP(2) and EP(4) receptors is coupled with an increase in cAMP, for which a cAMP analogue was found here to inhibit the ethanol-induced apoptosis. The increase in cAMP is known to activate both protein kinase A (PKA) and phosphatidylinositol 3-kinase pathways. An inhibitor of PKA but not of phosphatidylinositol 3-kinase blocked the PGE(2)-mediated protection of cells from ethanol-induced apoptosis, suggesting that a PKA pathway is mainly responsible for the PGE(2)-mediated inhibition of apoptosis. Based on these results, we considered that PGE(2) inhibited gastric irritant-induced apoptosis in gastric mucosal cells via induction of an increase in cAMP and activation of PKA, and that this effect was involved in the PGE(2)-mediated protection of the gastric mucosa from gastric irritants in vivo.

Pleiotropic effects of fatty acids on pancreatic beta-cells

Hyperlipidemia is frequently associated with insulin resistance states as found in type 2 diabetes and obesity. Effects of free fatty acids (FFA) on pancreatic beta-cells have long been recognized. Acute exposure of the pancreatic beta-cell to FFA results in an increase of insulin release, whereas a chronic exposure results in desensitization and suppression of secretion. We recently showed that palmitate augments insulin release in the presence of non-stimulatory concentrations of glucose. Reduction of plasma FFA levels in fasted rats or humans severely impairs glucose-induced insulin release. These results imply that physiological plasma levels of FFA are important for beta-cell function. Although, it has been accepted that fatty acid oxidation is necessary for its stimulation of insulin secretion, the possible mechanisms by which fatty acids (FA) affect insulin secretion are discussed in this review. Long-chain acyl-CoA (LC-CoA) controls several aspects of the beta-cell function including activation of certain types of protein kinase C (PKC), modulation of ion channels, protein acylation, ceramide- and/or nitric oxide (NO)-mediated apoptosis, and binding to nuclear transcriptional factors. The present review also describes the possible effects of FA on insulin signaling. We showed for the first time that acute exposure of islets to palmitate upregulates the intracellular insulin-signaling pathway in pancreatic islets. Another aspect considered in this review is the source of FA for pancreatic islets. In addition to be exported to the medium, lipids can be transferred from leukocytes (macrophages) to pancreatic islets in co-culture. This process consists an additional source of FA that may plays a significant role to regulate insulin secretion.

Up-regulation of COX-2 by inhibition of COX-1 in the rat: a key to NSAID-induced gastric injury

BACKGROUND

A recent study demonstrated that inhibition of both cyclooxygenase (COX)-1 and COX-2 is required for the development of nonsteroidal anti-inflammatory drug (NSAID)-induced gastric lesions. However, the role of COX-1 or COX-2 inhibition in the pathogenisis of these lesions remains unclear.

AIM

To examine the gastric ulcerogenic properties of selective COX-1 and COX-2 inhibitors in rats and to investigate further the relationship of COX inhibition to various events involved in the process of NSAID-induced gastric lesions.

METHODS

Animals were given various COX inhibitors p.o., either alone or in combination, and killed 8 h later. Under the treatment, gastric damage, prostaglandin (PG) E2 content, mucosal permeability, myeloperoxidase (MPO) activity as well as gastric motility were examined.

RESULTS

The nonselective COX inhibitor indomethacin inhibited PGE2 production, enhanced gastric motility, and provoked severe lesions in the stomach, with an increase in mucosal permeability and MPO activity. In contrast, the selective COX-2 inhibitor rofecoxib did not induce any damage in the stomach and had no effect on mucosal PGE2 content. Similarly, the selective COX-1 inhibitor SC-560 also caused no gastric damage, despite inhibiting PGE2 production. The combined administration of SC-560 and rofecoxib, however, provoked gross damage in the gastric mucosa, in a dose-dependent manner for each drug. SC-560, but not rofecoxib, caused marked gastric hypermotility and an increase in mucosal permeability, although an increase in MPO activity was observed only when rofecoxib was coadministered. The normal gastric mucosa expressed COX-1 mRNA and not COX-2 mRNA, but COX-2 mRNA was expressed in the stomach after administration of SC-560 as well as indomethacin but not rofecoxib.

CONCLUSION

These results suggest that the gastric ulcerogenic properties of NSAIDs are not accounted for solely by COX-1 inhibition, but require the inhibition of both COX-1 and COX-2. The inhibition of COX-1 up- regulates COX-2 expression, and COX-2/PGs may, in turn, counteract the deleterious affects of gastric hypermotility due to COX-1 inhibition.

Up-regulation of cyclooxygenase-2 by inhibition of cyclooxygenase-1: a key to nonsteroidal anti-inflammatory drug-induced intestinal damage

Nonsteroidal anti-inflammatory drugs (NSAIDs) induce gastrointestinal ulceration as the adverse reaction. This effect of NSAIDs is attributable to endogenous prostaglandin (PG) deficiency caused by inhibition of cyclooxygenase (COX), yet the relation between COX inhibition and the gastrointestinal ulcerogenic property of NSAIDs remains controversial. Using selective COX inhibitors, we examined whether inhibition of COX-1 or COX-2 alone is sufficient for induction of intestinal damage in rats. Various COX inhibitors were administered p.o. in rats, and the animals were killed 24 h later. Mucosal PGE2 levels were determined by enzyme immunoassay, whereas the gene expression of COX isozymes was examined by reverse transcription-polymerase chain reaction. Nonselective COX inhibitors such as indomethacin inhibited PGE2 production and caused damage in the small intestine. Selective COX-2 inhibitors (rofecoxib or celecoxib) had no effect on the generation of PG, resulting in no damage. A selective COX-1 inhibitor (SC-560) did not cause damage, despite reducing PGE2 content. However, the combined administration of COX-1 and COX-2 inhibitors provoked intestinal damage with an incidence of 100%. COX-2 was up-regulated in the small intestine after administration of SC-560, and the PGE2 content was restored 6 h later, in a rofecoxib-dependent manner. The intestinal lesions induced by SC-560 plus rofecoxib were significantly prevented by later administration of 16,16-dimethyl PGE2. These results suggest that the intestinal ulcerogenic property of NSAID is not accounted for solely by inhibition of COX-1 and requires inhibition of COX-2 as well. The inhibition of COX-1 up-regulates COX-2 expression, and this may be a key to NSAID-induced intestinal damage.

Is rabbit CLCA1 related to the basolateral Ca2+ -dependent Cl- channel of gastric parietal cells?

An expression of mRNA coding the calcium-activated Cl- channel-1 (CLCA1) in rabbit gastric parietal cells was examined to verify the possibility that the CLCA1 mediates housekeeping Cl- channels in the basolateral membrane. In whole-cell voltage-clamp experiments of rabbit parietal cells, A23187 (2 microM), a Ca2+ ionophore, activated the basolateral Cl- channels. The partial cDNA fragment of rabbit CLCA1 could be amplified from the total RNA of tracheal epithelium. A Northern blot analysis showed that rabbit CLCA1 mRNA of 3.4 kb is highly expressed in the tracheal epithelium, but not in the gastric parietal cells. Even in a more sensitive detection of rabbit CLCA1 mRNA by RT-PCR, no signal could be observed in the gastric parietal cells. These results suggest that the CLCA1 protein may not be a subunit of the housekeeping Ca2+ -dependent Cl- channel in the basolateral membrane of rabbit gastric parietal cells.

Inhibition of both COX-1 and COX-2 is required for development of gastric damage in response to nonsteroidal antiinflammatory drugs

We examined the gastric ulcerogenic property of selective COX-1 and/or COX-2 inhibitors in rats, and investigated whether COX-1 inhibition is by itself sufficient for induction of gastric damage. Animals fasted for 18 h were given various COX inhibitors p.o., either alone or in combination, and they were killed 8 h later. The nonselective COX inhibitors such as indomethacin, naproxen and dicrofenac inhibited PG production, increased gastric motility, and provoked severe gastric lesions. In contrast, the selective COX-2 inhibitor rofecoxib did not induce any damage in the stomach, with no effect on the mucosal PGE(2) contents and gastric motility. Likewise, the selective COX-1 inhibitor SC-560 also did not cause gastric damage, despite causing a significant decrease in PGE(2) contents. The combined administration of SC-560 and rofecoxib, however, provoked gross damage in the gastric mucosa, in a dose-dependent manner. SC-560 also caused a marked gastric hypermotility, whereas rofecoxib had no effect on basal gastric motor activity. On the other hand, the COX-2 mRNA was expressed in the stomach after administration of SC-560, while the normal gastric mucosa expressed only COX-1 mRNA but not COX-2 mRNA. These results suggest that the gastric ulcerogenic property of conventional NSAIDs is not accounted for solely by COX-1 inhibition and requires the inhibition of both COX-1 and COX-2. The inhibition of COX-1 up-regulates the COX-2 expression, and this may counteract the deleterious influences, such as gastric hypermotility and the subsequent events, due to a PG deficiency caused by COX-1 inhibition.