Biochemical and pharmacological characteristics of a newly synthesized H⁺-K⁺ ATPase inhibitor, YJA20379-1, 2-amino-4,5-dihydro-8-phenylimidazole [2,1-<i>b</i>]thiazolo[5,4-<i>g</i>]benzothiazole

Abstract

The biochemical and pharmacological characteristics of a newly synthesized H+-K+ ATPase inhibitor, 2-amino-4,5-dihydro-8-phenylimidazole[2,1-b]thiazolo[5,4-g]benzothiazole (YJA20379-1), were investigated. In the pig gastric microsomes, YJA20379-1 inhibited the gastric H+-K+ ATPase regardless of pH condition, IC50 values being 21 and 24 microM at pH 6.4 and 7.4, respectively. The inhibitory activity of YJA20379-1 was antagonized by dithiothreitol treatment but could not be reversed by dilution and washing of the enzyme preparation. In Sprague-Dawley rats, YJA20379-1, administered i.d., p.o, i.v., or s.c., significantly inhibited basal gastric acid secretion, with ED50 values of 4.7, 20.2, 6.3, and 13.4 mg/kg, respectively. The antisecretory action of YJA20379-1 was short lasting (less than 7 h at an oral dosing of 30 mg/kg). Oral administration of YJA20379-1 also prevented the formation of ethanol, indomethacin, and water immersion stress induced gastric lesions and mepirizole-induced duodenal ulcers in rats. Furthermore, YJA20379-1 accelerated the healing of acetic acid induced chronic gastric ulcers in rats. In conclusion, these results suggest that YJA20379-1 has a potent inhibitory activity on the gastric H+-K+ ATPase but much shorter duration of antisecretory action than omeprazole, thereby exerting its anti-ulcer effects partly with cytoprotective activity.