Biochemical and pharmacological properties of a newly synthesized proton pump (H+/K(+)-ATPase) inhibitor, TY-11345 in experimental animals

Anti-ulcerogenic properties of endothelin receptor antagonists in the rat

BACKGROUND

Endothelins have been implicated in gastric mucosal damage in a variety of animal models. Exogenous ET-1 and ET-3 are causally associated with experimental gastric ulcers. Furthermore, clinical reports also show elevated plasma and gastric mucosal endothelin-1 levels in patients suffering from peptic ulcers.

AIM

To study the possibility that endothelin receptor antagonists may have beneficial effects and prevent the development of gastric ulcers. We have tested in rats the orally-active endothelin antagonist bosentan (Ro 47-0203) and Ro 48-5695, which is 10-30 times more potent than bosentan on endothelin receptors.

METHODS

Water immersion restrained stress (WIRS) and indomethacin were used to provoke gastric mucosal damage. Endothelin receptor antagonists were administered orally prior to the induction of gastric damage. The gastric lesion index (mm), assessed macroscopically, and myeloperoxidase (MPO) activity were used as markers of the extent of mucosal injury.

RESULTS

Bosentan at 100 and 30 mg/kg administered orally caused attenuation of gastric damage in the WIRS model by 58% and 42%, respectively. Bosentan also caused complete reduction of MPO activity. In indomethacin-induced gastric damage, 100 mg/kg bosentan attenuated gastric damage by 45% and 61% as measured by the gastric lesion index and MPO activity respectively. Ro 48-5695 was at least 30 times more potent than bosentan in reducing indomethacin-induced mucosal damage and at 3 mg/kg, caused a decrease of 49% in the gastric lesion index and a reduction in MPO activity of 41%. Bosentan and Ro 48-5695 possess weak antisecretory properties as tested in the mouse gastric gland assay, than cannot, alone, account for their anti-ulcer properties.

CONCLUSIONS

Both endothelin receptor antagonists prevented the development of gastric mucosal injury in the rat. Disturbances in the gastric microcirculation are responsible for the development of experimental gastric ulcers. The anti-ulcer properties of these two endothelin antagonists suggest possible new therapeutic approaches to controlling gastric inflammation.

Tachykinin receptors on motoneurons in the spinal cords of neonatal rats, gerbils and hamsters

As a step to clarify the profiles of tachykinin receptors in the mammalian central nervous system, we examined the effects of various tachykinin receptor agonists and antagonists on motoneurons in isolated spinal cord preparations from rats, gerbils and hamsters. After treatment with tetrodotoxin, potential changes were recorded extracellularly from lumbar ventral roots at 27 degrees C. Bath-application of tachykinin NK1, NK3 receptor agonists produced depolarizing responses of ventral roots. In contrast, selective NK2 agonists exerted no or only marginal depolarizing action. Neurokinin A (NKA), however, exerted a distinct depolarizing action on motoneurons. Tachykinin NK1 receptor antagonists antagonized the actions of SPOMe and NKA in a competitive manner. The present results suggest that tachykinin NK1 and NK3 receptors are present on spinal motoneurons of newborn rats, gerbils and hamsters, and that NKA acts on the NK1 receptors.

Gastroprotective activity of the novel proton pump inhibitor lansoprazole in the rat

1. The protective activity of lansoprazole was evaluated on gastric mucosal lesions induced by intragastric 25% NaCl (1 ml/rat for 1 hr) and by indomethacin (20 mg/kg for 6 hr) in the rat and compared with that of omeprazole. 2. Lansoprazole (3, 10 and 10 mumol/kg i.g.) dose-dependently prevented the formation of indomethacin-induced lesions, the inhibition being 99% at the highest dose. Omeprazole, 10 mumol/kg i.g., enhanced the damage by indomethacin while higher doses caused a reduction, lesion index being reduced by 98% at 100 mumol/kg. 3. Histologically in lansoprazole- as well as in omeprazole-pretreated rats, indomethacin-induced necrosis of the mucosa was absent, luminal epithelium being intact. 4. Lansoprazole (30, 100 and 300 mumol/kg) and omeprazole (30, 100 and 300 mumol/kg) dose-dependently reduced the formation of lesions by hypertonic saline. 5. Present results indicated that lansoprazole and omeprazole protect the gastric mucosa in different experimental models of gastric ulceration.

Pharmacokinetic properties of a novel gastric proton pump inhibitor, (+/-)-2-[(4-methoxy-6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridin-9- yl)sulfinyl]-1H-benzimidazole sodium salt, in healthy subjects

The pharmacokinetics and safety of TY-11345 [(+/-)-2-[(4-methoxy-6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridin-9- yl)sulfinyl]-1H-benzimidazole sodium salt], a novel gastric proton pump inhibitor, were studied in healthy male volunteers after single (20, 40, and 80 mg) and repeated oral doses (60 mg, once daily for 7 days) as enteric-coated tablet. At the single doses of 20 and 40 mg, intragastric pH was continuously monitored in each of two subjects. No abnormal findings definitely attributable to the test drug were observed throughout the study. In the single-dose study, the maximum plasma concentration (Cmax) and area under the plasma concentration-time curve of TY-11345 increased in a dose-proportional manner. The time to reach Cmax was about 3 h after dosing and plasma concentrations declined thereafter with a half-life of about 1 h irrespective of dose. The effect of food intake on the pharmacokinetic parameters of TY-11345, which was evaluated at the dose of 40 mg in a cross-over design, was not significant. TY-11345 was not detected in urine unchanged, while a main metabolite and its conjugate were identified in urine as 32-38% of the dose. An intragastric pH value over 4 was obtained about 3 h after the administration of 40 mg and maintained for more than 5 h, despite the fall of plasma concentration. This effect was less obvious at a dose of 20 mg. In the multiple-dose study, the pharmacokinetics exhibited no substantial difference between the first and last doses.(ABSTRACT TRUNCATED AT 250 WORDS)