Effect of IT-066, a novel histamine H2 receptor antagonist, on human H2 receptors expressed in cho cells

April 1998 up and was perfumed with warmed Tyrode's solution. The basal part of the mucosal microcirculation was observed through a window made by partial removal of the serosa, smooth muscle and submucosa with fluorescence microscope. Fifty % ethanol (1 ml) was placed between the chamber and the gastric mucosa for 3 rain. Results The lucid fragments, which flowed from the collecting venule to the venule down stream, were not stained with acridine orange, suggesting that they may be white thrombi• Exposure of mucosa with 10-50% ethanol caused the mucosal damage in a concentration-dependent manner, in parallel with thrombus formation. Intravenous injection of anti-platelet serum (0.5 ml/rat) markedly reduced the circulating platelet number from 60xl04/mm 3 to 3xl04/mm3. Under this treatment, the reddened area after exposure of 30% ethanol was significantly (p < 0.05) reduced from 32 ± 4% (control serum, n=7) to 19 ± 3% (n=5). OKY-1581, a thromboxane A2 synthase inhibitor (10 mgkg, IV) significantly (p <0.05) reduced the reddened area from 3 4 ± 3 % (vehicle, n=7) to 20±3% (n=7). S-1452, a thromboxane Az antagonist (10 mg/kg. IV) significantly (p < 0.05) reduced the reddened area from 31 ± 2% (vehicle, n=4) to 19 ± 3% (n=4). A marked reduction (p < 0.05) in reddened area from 24 ± 6% (vehicle, n=6) to 3 ± 1% (n=5) was observed with a PGI2 derivative, beraprost sodium (0.3 mg/kg, intraduodenum), which did not cause the hypotensive response. L-NAME (10 mg/kg, IV) significantly (p < 0.01) increased the reddened area from 31 ± 5% (vehicle, n=5) to 60 ± 5% (n=5). Conclusions These results suggested that the platelet aggregation may be relevant to the development of the ethanol-induced gastric mucosal injury. G1012 EFFECT OF IT-066, A NOVEL HISTAMINE H2 RECEPTOR ANTAGONIST, ON HUMAN H2 RECEPTORS EXPRESSED IN CHO CELLS. H. Ohtsuka 1, T. Saitoh ~, M. Fukuyo t, N. Tamal 1, H. Mori 1, Y. Fukushima2, K. Sugano3, S. Ohkawa 1. 1Department of Medicine, Tokyo Women's Medical College, Daini Hospital, ZThird Department of Internal Medicine, 3Health Service Center, University of Tokyo, Tokyo, Japan Histamine H2 receptor antagonists are widely used for the treatment of peptic ulcer disorders. IT-066, a novel H2 receptor antagonist, reduces gastric acid secretion and heals experimental gastric ulcers in rats, dogs and rabbits. However, there are no reports concerning direct interactions of IT-066 with the human histamine H2 receptor. We cloned eDNA of the human histamine H2 receptor and expressed it in Chinese hamster ovary (CHO) ceils. Using this system, we compared the effect of IT-066 with those of other H2 receptor antagonists on histamine-dependent cAMP productions and on [H3]tiotidine bindings. A clone termed CHO-HH2, with an expression level of 280 fmol/10 s cells, was selected. Histamine-dependent cAMP productions and specific bindings of tiotidine were observed in CHO-HH2 ceils but not in control ceils, indicating that no endogenous I-I2 receptors are present in CHO cells. IT-066, ranitidine and famotidine inhibited cAMP production in response to 10-7 M histamine with IC~ovalues of 10.6.8 M, 10-5.6 M and 10.6.4 M, respectively. These agents were also inhibitory to 5 nM [3H]tiotidine bindings with IC~ovalues of 10-s M, 10-6.5 M and 10.7.4 M, respectively. Thus, IT-066 is a potent antagonist to the human histamine H2 receptor and this CHO expression system is useful for evaluating H2 receptor antagonists. G1013 SPONTANEOUSLY ItYPERTENSIVE RATS ARE MORE SUSCEPTIBLE TO ItCL-INDUCED GASTRIC DAMAGE THAN CONTROL STRAIN RATS: IMPLICATION OF GASTROPROTECTIVE ACTION OF ENDOGENOUS DOPAMINE. K, Ohtsuka 1,2, Y. Tatsumi l, T. Kodama l, M. Nishimura2, K. Kashimat, M. Yoshimura2. 1The Third Department of Internal Medicine, 2Department of Clinical and Laboratory Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan. Objective: Spontaneously hypertensive rats (SHR) have been reported to be less susceptible to stress-induced gastric ulcer because gastric sympathetic hyperactivity may prevent ulceration. However, it has not been investigated whether SHR is also less susceptibility to necrotizing agent-induced gastric damage and whether the regional catecholamines in the stomach are responsible against ulceration. We studied whether SHR, compared with Wistar-Kyoto rats (WKY), are resistant against HCl-induced gastric ulceration and estimated the change of gastric catecholamine contents after HC1 administration. Design and Methods: Rats were given 3 ml/kg of IN HCI orally for induction of gastric lesions. Gastric mucosal damage was estimated as the area of mucosal breaks. Endogenous catecholamine contents in the gastric corpus and antrum were measured by method of high-performance liquid chromatography 6, 12, 18 and 24 hours after HCI administartion and compared with the control rats. Results: HCl-induced gastric erosion and ulcer of SHR were more severe than those of WKY. Dopamine contents in the corpus and antrum of SHR decreased significantly after ulceration, while those in corpus of WKY increased significantly after ulceration. Norepinephrine contents in the gastric wall of both SHR and WKY did not increase after gastric ulceration. Conclusions: Our results suggest that the more severe extent of the HCIinduced gastric lesions in SHR than that in WKY may be due to the different response of gastric dopamine after HC1 administration between SHR and WKY, and it may lead to the conclusion that endogenous dopamine plays an important role for gastroprotection.

Esophageal, Gastric, and Duodenal Disorders A247

GI014 EFFECTS OF HELICOBACTER PYLORI ERADICATION ON INSULIN-DEPENDENT DIABETES MELLITUS, V Ojetti, A Gasharrini, D Pitocco, F Franceschi, E Sanz Torre, M Candelli, A De Luca, R Nocente, G Ghirlanda, G Gasbarrini. Internal Medicine and Diabetology, Catholic University of Rome; Ricerca in Medicina, Bologna; Italy. Insulin-dependent diabetes mellitus (IDDM) is the result of the progressive autoimmune destruction of the Islets of Langerhans's ]3 cells. H. pylori has been recently associated to some autoimmune diseases, such as Sjogren syndrome and thyroiditis. Aim of the study was to assess the prevalence of infection and the effects of bacterium eradication on IDDM management. METHODS: 119 patients (pts) (68 males and 51 females, mean age: 35 ± 11 yrs) consecutive affected by IDDM were evaluated• H. pylori infection was determined by t3C-urea breath test; the presence of the cytotoxins CagA and VacA was evaluated through Western Blot analysis. Triple therapy consisting of amoxicillin (500 mg qid), clarithromycin (250 mg tid) and pantoprazole (40 mg bid) was given to patients at the time of diagnosis for 7 days. Control of eradication was assessed by 13C urea breath test after 6 weeks of finishing treatment. Gastrointestinal (GI) symptoms (bloating, pyrosis, epigastric pain, belching, alitosis, nausea) and daily dosage of insulin were assessed at enrollment and after 12 weeks from eradication. RESULTS: H. pylori infection resulted in 35% of the IDDM pts (42 out of 119). Mean age resulted significantly higher in infected pts (40 ± 12 vs 33 ± 10 yrs; p < 0.01). CagA and VacA cytotoxins were found in 70 and 44% of infected pts, respectively. Infection rate increased significantly with age and duration of IDDM. H. pylori positive pts showed a significantly higher prevalence of bloating (71 vs 46%; p < 0.009), pyrosis (47 vs 29%; p < 0.05) and epigastric pain (38 vs 20%; p < 0.04) when compared to negative pts. No differences were found between infected and uninfected patients as regards to the other GI symptoms evaluated and the dally dosage of insulin (43 ± 20 vs 40 ± 18 IU/die, respectively). 26% (11/42) of infected patients did not complete the eradication treatment and were considered as drop out; only 65% (20/31) of the patients which completed therapy were eradicated. Epigastric pain, pyrosis, belching and alitosis resulted significantly reduced after eradication; conversely, none of those were reduced in treated but non eradicated pts. Dally dosage of insulin was not affected by H. pylori eradication. CONCLUSIONS: H. pylori infection does not appear to be linked to IDDM pathogenesis. Interestingly, infected pts presented a low eradication rate and a higher prevalence of only some of the GI symptoms evaluated. • G1015

H. PYLORI (HP) SEROLOGY IS UNHELPFUL IN THE MANAGEMENT OF AFRICAN PATIENTS WITH DYSPEPSIA. SJD O'Keefe, J Nainkin, B Salvador, S Majiki, H Stevens, A Atherstone. Dept.sMedicine, Surgery, Pathology, Cecelia Makiwane Hospital, Mdantsane, Eastern Cape, S. Africa. Empiric treatment of dyspepsia based on HP serology(HPser) testing has been claimed to be cost-effective in the USA. This approach would be attractive in rural Africa, where resources are limited. However, the discriminant value of HPser may be reduced in countries such as South Africa where the prevalence of chronic HP infection in the community is over 80%. Consequently, we examined the association between HPser and endoscopic findings in dyspeptic African patients in 4 rural regions of the Ciskei and Transkei. After outpatient assessment, 108 individuals with dyspepsia (45M, 63F, median age 54, range 14-90yrs) were selected for endoscopy following blood sampling for HPser (CobasCore Kit: lgG E1A, > 95.5% sans, > 97.7% spec, Roche, UK. Titre > 100units -- positive). number (%)

HPab (units)

HP% pos.

NUD normal gastritis

39 (36) 23 (21)

634 ± 127 565 ± 253

82 83

PUD duodenal ulcer gastric ulcer

10 (9) 8 (7)

961 ± 338 469 ± 172

90 87

CANCER esophageal gastric duodenal ESOPHAGITIS TOTAL

12 (11) 4 (4) 1 (1) 10 (9) 108 (100)

356 ± 120 907 ± 440 3333 308 ± 118 629 ± 87

67 50 100 70 80

In comparison to dyspeptics in the West, more Africans were HP+ and had neoplastic disease, principally because of endemic sq. Ca. esophagus. Neither HP status, nor HPab levels helped predict the presence of serious disease. Patients with alarm signs (568 ± 139units) and with esophageal cancer (356 ± 120) had, if anything, lower antibody levels than patients with simple dyspepsia (685 ± 130). In conclusion, the poor predictive value of HPser for the presence of serious underlying disease in Africans argues strongly for a) the use of early endoscopy rather than empiric treatment of dyspeptics, and b) supports the view that chronic HP infection is a "normal" finding in rural Africans.