Adjunct antibiotic combination therapy for steroid-refractory or -dependent ulcerative colitis: an open-label multicentre study.

BACKGROUND: We previously demonstrated that antibiotic combination therapy is effective for induction and maintenance of ulcerative colitis (UC) remission. AIM: To assess whether antibiotic combination therapy is effective for active UC refractory to or dependent on steroids in a multicentre, open-label trial. METHODS: We enrolled 30 patients with steroid-refractory and 64 with steroid-dependent active UC. These patients received three-times-daily by mouth amoxicillin 500 mg, tetracycline 500 mg and metronidazole 250 mg, for two weeks, as well as conventional treatment. Symptom assessment and colonoscopic evaluation were performed before enrolment and at 3 and 12 months after treatment completion. Clinical response was defined as a Lichtiger symptom score decrease in ≥3 points and clinical remission as a score ≤4. RESULTS: Nineteen of the 30 steroid-refractory (63.3%) and 47 of the 64 steroid-dependent (73.4%) patients showed a clinical response within 2 weeks. At 3 and 12 months, 60% and 66.6% of steroid-refractory patients, and 56.3% and 51.6% of steroid-dependent patients, respectively, achieved clinical remission. In the steroid-dependent group, 39 of the 64 patients (60.9%) were able to stop steroid therapy and remained in remission for 3 months. Three (10%) steroid-refractory and four (6.3%) steroid-dependent patients underwent colectomy. CONCLUSIONS: This multicentre, long-term follow-up study suggests 2 week antibiotic combination therapy to be effective and safe in patients with active UC refractory to or dependent on steroids.

Role of the nrf-2 gene in protection and repair of gastric mucosa against oxidative stress.

Helicobacter pylori infection, as well as NSAIDs induce oxidative stress on gastric mucosa, thereby causing mucosal damage and retarding mucosal repair. Cells can survive against chronic oxidative stress by enhancing activities of anti-oxidant enzymes, thereby protecting cells from DNA damage. Recent studies have clearly shown that the gene encoding Nrf-2 (NF-E2 p45-related factor-2) plays an important role in the induction of antioxidant enzymes against oxidative stress. In this paper, we will describe the cellular mechanisms by which the nrf-2 gene stimulates anti-oxidant enzyme activities during exposure to oxidative stress. Secondly, we will also mention the beneficial effects of sulforaphane, an isothiocyanate family which is abundantly included in broccoli sprouts, on gastric mucosa. Sulforaphane stimulates nrf-2 gene-dependent anti-oxidant enzyme activities, thereby protecting cells from oxidative injury. Finally, we will state our perspective on the efficacy of sulforaphane in protection and repair of gastric mucosa against oxidative stress during H. pylori infection.

Autofluorescence in indomethacin-induced gastric mucosal lesions in rats.

Autofluorescence observations enable scientists to sensitively identify various lesions. Non-steroidal anti-inflammatory drugs such as aspirin and indomethacin are well known to induce gastric mucosal injuries. Our purpose was to clarify whether the observation of mucosal autofluorescence could help us to recognize indomethacin-induced gastric lesion formation. Gastric mucosal fluorescence intensity and gastric lesion scores were time-sequentially measured after indomethacin treatment in rats. To identify the localization of autofluorescent substances, stomach cryosections were observed with an epifluorescence microscope. Fluorescent substances from damaged tissue were also analyzed by high-performance liquid chromatography. In addition, to elucidate whether oxidative stress directly generates fluorescent substances from heme, we investigated the reaction between hydrogen peroxide and hemoglobin in a cell-free system. Treatment with indomethacin induced gastric lesions by tissue peroxidation, with mucosal fluorescence intensity increasing time-dependently. The fluorescence products were mesoporphyrin and protoporphyrin, and they were localized in disrupted mucosal tissue. In the cell-free system, porphyrins were directly generated by hydrogen peroxide from hemoglobin. These findings indicate that indomethacin treatment increased the intensity of porphyrin fluorescence. Gastric mucosal lesion formation can be sensitively detected with fluorescence observations.

Luminal ammonia retards restitution of guinea pig injured gastric mucosa in vitro.

The present study was conducted to elucidate the mechanisms by which Helicobacter pylori (HP)-derived ammonia causes gastric mucosal injury. Intact sheets of guinea pig gastric fundic mucosae were incubated in Ussing chambers. Both the luminal and the serosal pH were kept at 7.4. Transmucosal potential difference (PD) and electrical resistance (R) were monitored as indices of mucosal integrity. Restitution was evaluated by recovery of PD, R, and transmucosal [(3)H]mannitol flux after Triton X-100-induced mucosal injury. The effects of luminal or serosal NH(4)Cl on function and morphology of uninjured or injured mucosae were examined. In uninjured mucosae, serosal NH(4)Cl induced more profound decreases in PD and R and more prominent vacuolation in gastric epithelial cells than did luminal NH(4)Cl. In contrast, luminal NH(4)Cl markedly inhibited restitution in injured mucosae and caused an extensive vacuolation in gastric epithelial cells, as did serosal NH(4)Cl. Transmucosal ammonia flux was greater in the injured than in the uninjured mucosae. These results suggest that 1) basolateral membrane of gastric epithelial cells is more permeable to ammonia than apical membrane and 2) luminal ammonia, at concentrations detected in HP-infected gastric lumen, retards restitution in injured mucosae.

[Effects of Helicobacter pylori(Hp) eradication on gastric mucosal pathophysiology in Hp-positive, NSAIDs-induced gastric ulcer].

It has been suggested that the mechanisms of NSAIDs-induced peptic ulcer disease are totally different from those induced by Hp. Although a number of studies have examined the effects of Hp eradication on pathophysiology of NSAIDs-induced ulcer diseases, the results have been controversial. At present, therefore, we do not know whether Hp should be eradicated in Hp-positive NSAIDs-induced ulcer patients. Recent studies have shown that both Hp eradication and NSAIDs treatment increases gastric acid secretion, and often causes mucosal lesions in upper GI tract. Based on this back ground, we have decided to review pathophysiology of the Hp-dependent ulcer, and the NSAIDs-induced ulcer. We also discussed the merit and demerit of Hp eradication on gastric mucosal pathophysiology in Hp-positive, NSAIDs-induced ulcer.

Steroid-refractory severe ulcerative colitis responding to cyclosporine and long-term follow-up.

We report a case of steroid-refractory ulcerative colitis, treated with cyclosporine, in a 38-year-old woman with a 13-year history of ulcerative colitis. No remission was achieved with treatments that included intravenous hyperalimentation, sulfasalazine, and intensive parenteral prednisolone therapy for 4 weeks. Intravenous infusion of cyclosporine was performed because the patient refused to undergo surgery. Her condition improved dramatically and colectomy was avoided. She has been maintained on oral cyclosporine and azathioprine since steroids were discontinued, and she has remained in clinical and endoscopic remission for 2 years. The side effects were not significant, but mild paresthesia in both hands and mild hypertension, which was controlled by anti-hypertensives. Cyclosporine seems to be an effective treatment for patients with steroid-refractory severe active ulcerative colitis in whom colectomy seems inevitable. We believe further clinical trials of the treatment are warranted.

Miconazole gel increases the cure rate of Helicobacter pylori infection when added to lansoprazole and amoxicillin in a randomized trial.

BACKGROUND: Miconazole is an antimycotic agent with bacteriocidal activity against Helicobacter pylori in vitro. Its role in the clinical eradication of H. pylori has not been studied. The objective of this study was to investigate the efficacy and side effect profile of miconazole for the treatment of H. pylori. MATERIALS AND METHODS: We studied 65 patients with gastritis or peptic ulcer disease in whom H. pylori infection was confirmed by a rapid urease test and microbiologic assessment. In vitro miconazole sensitivity was assessed for the H. pylori strains isolated from the enrolled patients. All patients were randomized to receive either dual therapy consisting of lansoprazole 30 mg daily and amoxicillin 500 mg three times a day for 14 days (LA, n = 33) or triple therapy using the LA regimen plus miconazole gel 100 mg three times a day for 14 days (LAM, n = 32). At least 8 weeks after the treatment, successful therapy was validated by the histological and microbiologic assessment. Adverse effects and drug adherence were monitored by direct questioning. RESULTS: The minimum inhibitory concentrations of miconazole ranged from 3.13 to 6.25 mg/L. H. pylori was eradicated in 16 of 33 patients (48%, 95% CI = 31% to 67%) after LA therapy, and 24 of 32 patients (75%, 95% CI = 59% to 91%) after LAM therapy (p < .03). There was no significant difference in the occurrence of adverse events between the two groups. CONCLUSIONS: The addition of miconazole gel to the LA regimen significantly improved the cure rate of H. pylori without an increase in adverse effects.

Role of transforming growth factor-beta in the restitution of injured guinea pig gastric mucosa in vitro.

The role of transforming growth factor-beta (TGF-beta) in restitution was examined in intact sheets of injured guinea pig gastric mucosa in which the epithelial cell-collagen interaction can be quantitatively evaluated. The luminal surface of intact sheets of in vitro guinea pig gastric mucosa was injured by exposure to 1.25 mol/l NaCl for 10 min. Restitution was evaluated by measurement of transmucosal electrical resistance and [3H]mannitol flux before and after injury. Recovery of electrical resistance and [3H]mannitol flux was retarded by inhibition of endogenous TGF-beta with either aprotinin or anti-TGF-beta antibody; effects were restored by human recombinant TGF-beta1. During inhibition of endogenous TGF-beta, type IV collagen accelerated the recovery. Inhibition of reconstruction of the basement membrane by simultaneous addition of cis-4-OH-L-proline and anti-type IV collagen completely abolished the enhancement of the recovery by TGF-beta 1. These results suggest that endogenous TGF-beta is required for restitution to occur in guinea pig gastric mucosa and that type IV collagen plays an important role in TGF-beta-abetted restitution.

Role of nitric oxide in restitution of injured guinea pig gastric mucosa in vitro.

The role of nitric oxide (NO) in restitution was examined in intact sheets of in vitro guinea pig gastric mucosae after mucosal injury induced by exposure of the luminal surface to 1.25 M NaCl for 10 min. The recovery of transmucosal electrical resistance and [3H]mannitol flux after the injury were significantly greater at luminal pH (pH1) 7.0 than 3.0. The recovery was abolished by pretreatment with 1 mM NG-nitro-L-arginine methyl ester (L-NAME), only at pHL 3.0, an effect reversed by 1 mM L-arginine. Enhancement of the recovery by L-arginine at pHL 3.0 was abolished by 50 microM methylene blue (MB), an effect restored by 1 mM N6,2'-O-dibutyryl guanosine 3',5'-cyclic monophosphate (DBcGMP). In L-arginine- but not L-NAME-treated tissues, recovery was enhanced further by an increase in serosal [HCO3-] and was inhibited by 5% N-acetyl-L-cysteine in the luminal solution or by the removal of serosal HCO3-. Morphological examination showed the formation of a thick "mucoid cap" in L-arginine-but not L-NAME-treated tissues. These results suggest that, in the presence of luminal acid, endogenous NO contributes to restitution in injured gastric mucosa at least in part by facilitating the formation of the mucoid cap.

Localization of brush border cytoskeletal proteins in gastric oxynticopeptic cells from the bullfrog Rana catesbeiana.

The contribution of brush border cytoskeletal proteins (actin, villin, fimbrin, and brush border myosin-1) to organization of the cytoskeletal network underlying apical plications of oxynticopeptic cells was examined by immunohistochemical techniques in frozen sections of gastric mucosa from the bullfrog, Rana catesbeiana. Apical localization of F-actin with phalloidin in oxynticopeptic cells inhibited with cimetidine revealed small, punctate domains within the apical cytoplasm that were consistent with the presence of short microvilli revealed by electron microscopy. Localization of F-actin in cells stimulated with forskolin was limited to a wide continuous band of cytoplasm corresponding to the location of numerous long surface folds. Inhibition of protein synthesis with cycloheximide did not prevent acid secretion or formation of actin filaments within surface folds in stimulated oxynticopeptic cells, suggesting that the formation of filaments does not require actin synthesis. Staining of gastric mucosae with fluorescent DNase-1 demonstrated that oxynticopeptic cells possess an unusually large pool of non-filamentous actin. Taken together, these results suggest that actin-filament formation in stimulated cells occurs by polymerization of an existing pool of non-filamentous actin. Localization of antibodies specific for villin and fimbrin revealed that these proteins were present within intestinal absorptive cells and gastric surface and neck cells but were not present within inhibited or stimulated oxynticopeptic cells. Brush border myosin-1, present in intestinal absorptive cells, was not present in gastric epithelium. Thus, we propose that actin-containing projections in oxynticopeptic cells are not organized like intestinal microvilli and that filament formation occurs after stimulation by modulating intracellular pools of filamentous and non-filamentous actin.

Effects of ammonium ion and ammonia on function and morphology of in vitro frog gastric mucosa.

The effects of ammonium ion (NH+4) and ammonia (NH3) on function and morphology of gastric epithelial cells were studied in intact sheets of in vitro frog (Rana catesbeiana) gastric mucosa. Luminal 115 mM NH4Cl at luminal pH 8.0 (calculated [NH3] 2.7 mM), but not at 5.0 (calculated [NH3] 3 microM) induced 1) an increase in intracellular pH (pHi) in oxynticopeptic cells (OPC) and decreases in transmucosal potential difference (PD) and electrical resistance (R) in resting tissues, 2) a decrease in histamine-stimulated H+ secretion and an increase in H+ backdiffusion after removal of luminal NH4Cl, and 3) augmented acidification of OPC during luminal acidification. Serosal 30 mM NH4Cl at serosal pH 7.2 (calculated [NH3] 0.47 mM) induced 1) an increase in pHi in OPC and inhibition of the alkalinization of OPC after removal of ambient Cl-, 2) a decrease in PD associated with the increase in R and decrease in short-circuit current, effects attenuated by serosal 15 mM K+, accentuated by 0.2 mM Ba2+, and abolished by removal of ambient Cl-, 3) a sudden drop of PD in resting, but not in stimulated tissues, effects prevented by high serosal pH (7.8), serosal HCO3-, or removal of luminal Cl-, 4) a decrease in histamine-stimulated H+ secretion and an increase in H+ backdiffusion after removal of NH4Cl, and 5) augmented acidification of OPC during luminal acidification. These results suggest that 1) luminal NH3, but not NH+4, increases backdiffusion of H+ from the lumen to the mucosa, 2) serosal NH3 and/or NH+4 induces depolarization of OPC and decreases electrogenic Cl- transport, thereby attenuating the activity of the basolateral Cl(-)-HCO3- exchanger in OPC, and 3) both of these effects contribute to the augmented acidification of OPC during exposure to high luminal [H+].

Cell survival in rabbit gastric glands: effect of extracellular pH, osmolarity, and anoxia.

Although backdiffusion of luminal acid is regarded as a common mechanism of gastric injury, the extracellular pH (pHo) at which cells are irreversibly injured is not well defined. Exclusion of the fluorescent dye propidium iodide was used to estimate cell survival in rabbit gastric glands incubated in buffers of pHo 8.0-2.0. Mean survival (+/- SE) for n = 6 experiments at 2 h in a HEPES buffer of 300 mosM at pHo 8.0, 7.0, 6.0, 4.0, and 2.0 was 80 +/- 3, 91 +/- 2, 90 +/- 2, 71 +/- 2, and 17 +/- 4%, respectively. Survival at acidic pHo was improved in a high KCl buffer: 78 +/- 3 and 38 +/- 7% at pHo 4.0 and 2.0, respectively. Survival in HCO3- buffers was 73 +/- 3, 88 +/- 2, and 92 +/- 3% at pHo 8.0, 7.4, and 6.0. Brief (5 min) exposure to pHo 4.0 followed by reexposure to pHo 7.4 had no effect on acid secretion as estimated by [14C]aminopyrine uptake or cellular viability over 4 h. The influence on cell survival of changes in pHo under conditions of chemical anoxia and in buffers of different osmolarity was investigated. Chemical anoxia was induced using 2.5 mM KCN and 2.0 mM iodoacetic acid (IAA) to inhibit oxidative phosphorylation and anaerobic glycolysis. Survival in glands exposed to KCN and IAA in HEPES buffer was 54 +/- 5, 82 +/- 3, and 87 +/- 2% at pHo 8.0, 7.0, and 6.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of hypoxia on function and morphology of in vitro frog gastric mucosa.

The effects of gaseous hypoxia and reoxygenation on oxynticopeptic (OPC) and surface mucous cells (SMC) were examined in in vitro bullfrog gastric fundic mucosae mounted in Ussing chambers. Forskolin-stimulated H+ secretion, transmucosal potential difference (PD), and electrical resistance (R) were monitored in tissues incubated in HCO3(-)-free or HCO3(-)-containing buffer. At serosal pH (pHs) 7.2, 1 h of hypoxia with 100% N2 resulted in a decrease in PD, increase in R, and complete inhibition of H+ secretion. After 30 min of hypoxia, the morphology of OPC changed from the secretory to the nonsecretory state without recognizable cytopathology. Destructive changes in OPC increased progressively at pHs 7.2 as the hypoxic period was prolonged from 4 to 24 h. After 4 h of reoxygenation following 12-24 h of hypoxia, OPC remained necrotic and H+ secretion showed no recovery, whereas in some areas where SMC were exfoliated adjacent SMC showed epithelial restitution. The recovery of H+ secretion and PD during 2 h of reoxygenation after 4 h of hypoxia at pHs 6.0 and 6.8 was less than that at 7.2 and 8.0 and was greater in the presence of serosal HCO3- than its absence at pHs 7.2. These results suggest that, in in vitro frog gastric mucosa, 1) OPC are more vulnerable to hypoxia than SMC, 2) basolateral acidosis exaggerates hypoxic injury of OPC, and 3) serosal HCO3- protects OPC from hypoxic injury.

Prostaglandin stimulates Cl(-)-HCO3- exchange in amphibian oxynticopeptic cells.

Prostaglandins, shown to stimulate Cl- transport in epithelial cells of several different tissues, protect gastric mucosa against physiological injury induced by luminal acid. To clarify the relationship between the stimulation of Cl(-)-transport and the protection of gastric mucosa, the effect of prostaglandin on Cl(-)-HCO3- exchange in oxynticopeptic cells (OPC) was examined in intact sheets of in vitro frog gastric mucosa, in which OPC were selectively loaded with the pH-sensitive fluorescent dye 2',7'-bis(carboxyethyl)-5(6')-carboxyfluorescein (BCECF). In omeprazole (0.3 mM)-pretreated frog fundic mucosae, in which H+ secretion was totally inhibited, 16,16-dimethyl prostaglandin E2 (dmPGE2) induced a significant decrease in intracellular pH (pHi) in OPC simultaneously with a significant increase in pHi in adjacent muscularis mucosae, an effect abolished by removal of ambient Cl- or addition of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) (0.5 mM). dmPGE2 accentuated the rates of alkalinization of OPC after either removal of ambient Cl- or addition of serosal H2DIDS. During exposure to luminal or serosal acid, dmPGE2 significantly attenuated acidification of OPC induced by the exogenous H+, effects abolished either by removal of ambient Cl- or by addition of H2DIDS (0.5 mM). These results suggest that 1) dmPGE2 stimulates extrusion of HCO3- through the basolateral Cl(-)-HCO3- exchanger in resting OPC (H+ secretion inhibited) and that 2) relatively high extracellular [HCO3-] on the basolateral surface afforded by dmPGE2 protects OPC from acidification during exposure to luminal or serosal acid.

H(+)-K(+)-ATPase contributes to regulation of pHi in frog oxynticopeptic cells.

The effect of intracellular acidosis on luminal H+ secretion and the role of H(+)-K(+)-ATPase in regulation of intracellular pH (pHi) in oxynticopeptic cells (OPC) (measured with a pH-sensitive fluorescent dye) were examined in intact sheets of in vitro frog (Rana catesbeiana) gastric mucosa. Intracellular acidosis of OPC induced by decreasing pH in the serosal solution (pHs) from 7.2 to 6.0 reversibly increased forskolin-stimulated H+ secretion without increasing endogenous histamine release. The observed increase in H+ secretion was unaffected by either 1 mM cimetidine or 1 mM histamine, but was accentuated by 1 mM amiloride, an effect abolished by 0.3 mM omeprazole. Steady-state pHi values in stimulated or resting OPC at pHs 7.2 were not significantly different. However, pHi in OPC was significantly higher in stimulated than in resting tissues at pHs 6.9, a difference accentuated by decreasing pHs to 6.4 or by 1 mM amiloride. Amiloride completely prevented recovery from intracellular acidosis induced by pHs 6.4 or 6.9 in omeprazole-treated tissues, but only partially mitigated recovery in cimetidine- or forskolin-treated tissues. At pHs 6.4, high luminal [K+] (100 mM) increased H+ secretion and hastened recovery of pHi in cimetidine-treated tissues in the presence of amiloride. These results suggest that, in intact sheets of in vitro frog gastric mucosa, 1) intracellular acidosis stimulates luminal H+ secretion via histamine-independent mechanisms and 2) H(+)-K(+)-ATPase contributes to the recovery of OPC from intracellular acidosis.

Impaired neutralizing capacity of duodenal mucosa following luminal acidification in recurrent duodenal ulcer.

To investigate the role of the mucus-bicarbonate barrier in the prevention of duodenal ulcer recurrence, duodenal mucosal neutralizing capacity and mucosal prostaglandin (PG) synthesis were examined in 5 normal controls (NC) and 12 duodenal ulcer (DU) patients. DU patients were divided into non-recurrent (NR,7) and recurrent (R,5) groups based on endoscopic follow-up study. The recovery time (RT) was significantly longer and the mucosal PGE2 synthesis was significantly lower in R than in NC and NR groups. There was a proportional correlation between mucosal PG synthesis and RT in DU These results indicate that impaired neutralizing capacity caused by reduced endogenous PG synthesis in duodenal mucosa may contribute to recurrence of DU.

Effect of luminal acid on intracellular pH in oxynticopeptic cells in intact frog gastric mucosa.

The effect of changes in luminal [H+] on intracellular pH in oxynticopeptic cells was examined using intact sheets of frog (Rana catesbeiana) gastric mucosa in which oxynticopeptic cells were selectively loaded with the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The serosal solution was buffered with either HCO3- or N-2-hydroxymethylpiperazine-N'-2-ethanesulfonic acid (HEPES). Luminal pH was decreased from 7.2 to 1.5 and changed back to 7.2. In stimulated (forskolin-treated) tissues, intracellular pH decreased at luminal pH 1.5 only in HEPES, with complete recovery at 7.2. In resting (omeprazole-treated) tissues, intracellular pH began to decrease at luminal pH 2.0 in HEPES and at 1.5 in HCO3-, with complete recovery at 7.2 in both. In resting tissues bathed in Cl(-)-free HEPES, the recovery of intracellular pH at luminal pH 7.2 was completely prevented by serosal amiloride (1 mmol/L) but was not affected by serosal 4,4'-diisothiocyanatodihydrostilbene-2-2'-disulfonic acid (H2-DIDS; 0.5 mmol/L). In resting tissues bathed in Cl(-)-free HCO3-, the recovery of intracellular pH at luminal pH 7.2 was not affected by amiloride but was prevented partially by H2-DIDS and completely by combination of H2-DIDS and amiloride or by removal of ambient Na+. These results suggest that during exposure to high luminal [H+]: (a) stimulated oxynticopeptic cells maintain a steady intracellular pH more readily than resting cells; (b) serosal HCO3- protects oxynticopeptic cells from intracellular acidosis; and (c) both Na+/H+ exchange and Na(+)-HCO3- cotransport are involved in the recovery from intracellular acidosis in resting oxynticopeptic cells.

Effect of basolateral acidification on the frog oxynticopeptic cell.

The effects of intracellular acidosis induced by acidification of the basolateral (nutrient) perfusate on the structure and function of the oxynticopeptic cell were studied in in vitro frog gastric mucosa. Changing the pH of the unbuffered nutrient perfusate (UNB) from 7.2 to 3.5 acidified the oxynticopeptic cell with no change in potential difference (PD) or resistance (R). Intracellular pH (pHi), PD, and R were 7.05 +/- 0.01, 16 +/- 1 mV, 165 +/- 7 omega.cm2 before and 6.44 +/- 0.01, 16 +/- 2 mV, 170 +/- 9 omega.cm2 after nutrient acidification. Acid secretion (H+) increased from 0.86 +/- 0.07 to 1.88 +/- 0.18 mu eq.cm-2.h-1. Addition of forskolin to tissues perfused with nutrient pH (pHn) 3.5 decreased PD to 2 +/- 2 mV and further increased H+ to 3.07 +/- 0.19 mu eq.cm-2.h-1. By light and electron microscopy oxynticopeptic cells perfused with UNB, pHn 3.5, appeared normal. Oxynticopeptic cells in tissues pretreated with omeprazole and then exposed to UNB, pHn 3.5, had extensive morphological damage. On increasing the pH of the nutrient perfusate from 3.5 to 7.2 there was prompt recovery of pHi in untreated and forskolin-stimulated mucosae (pHi 6.87 +/- 0.06 and 6.85 +/- 0.04) but no recovery of pHi in tissues pretreated with omeprazole or cimetidine (pHi 6.26 +/- 0.04 and 6.44 +/- 0.06, n = 6, 30 min after reexposure to UNB, pHn 7.2). We conclude that in a secreting mucosa intracellular acidification of the oxynticopeptic cell to pHi 6.4 is associated with normal morphology, PD, R, and increased H+, and that intracellular acidosis is not de facto deleterious.

Influence of Cl- on pH(i) in oxynticopeptic cells of in vitro frog gastric mucosa.

The effect of Cl- on intracellular pH (pH(i)) was studied using sheets of frog (Rana catesbeiana) fundic mucosa in which oxynticopeptic cells were selectively loaded with the acetomethoxy ester form of the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF/AM). Before the measurement of pH(i), tissues were exposed to either 10(-5) M forskolin in the serosal solution (stimulated tissues) or 3 x 10(-4) omeprazole in the serosal solution (inhibited tissues). In HCO3- and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffers, pH(i) increased significantly after removal of Cl- from serosal and luminal solution, both in stimulated and inhibited tissues. The presence of Cl- in the luminal solution prevented this rise in pHi, an effect abolished by serosal 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS, 3 x 10(-4) M) but not by serosal amiloride (10(-3)M). In the presence of serosal Cl-, pH(i) increased after exposure to serosal DIDS, more prominently in the stimulated than in the inhibited tissues. These results confirm the presence of a Cl(-)-HCO3-exchanger in the basolateral membrane of oxynticopeptic cells in intact sheets of mucosa and suggest that luminal Cl- contributes to the regulation of pH(i) in oxynticopeptic cells.