Effects of H2-receptor antagonists cimetidine, ranitidine, and ICi 125,211 on histamine-stimulated adenylate cyclase activity in guinea pig gastric mucosa

Cheret, A.M.; Pignal, F.; Lewin, M.J.

Molecular Pharmacology 20(2): 326-330

1981


ISSN/ISBN: 0026-895X
PMID: 6117786
Accession: 068627052

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Abstract
Histamine stimulation of adenylate cyclase activity in broken cells isolated from guinea pig gastric mucosa was competitively inhibited by the thiazole derivative ICI 125,211 of 7.62 (Ki = 2.39 .times. 10-8 M) and pA2 of 6.90 (Ki = 1.25 .times. 10-7 M), respectively, i.e., potencies 19 times and 4 times superior to that of the classical H2-receptor antagonist cimetidine (pA2 = 6.34; Ki = 4.57 .times. 10-7 M). These results are consistent with the reported pharmacological potencies of the antagonists on guinea pig right atrium and on gastric acid secretion in vivo. Thus, the requirement of an imidazole ring in the structure of H2-receptor antagonists can be definitely ruled out.