ESTIMATION OF pKB VALUES FOR HISTAMINE H2‐RECEPTOR ANTAGONISTS USING AN in vitro ACID SECRETION ASSAY

Abstract

Histamine H2‐receptor antagonism by burimamide, metiamide and cimetidine was analysed under apparent equilibrium conditions in the lumen‐perfused isolated stomach preparation of the mouse. The behaviour of these compounds was not incompatible with simple competitive antagonism but the estimated pKB values (−log KB) were all significantly lower, by about 1 log unit, than reference values reported for guinea‐pig atrium or rat uterus. There seems no need to propose that the parietal cell receptors are somehow different from the others; metiamide continually appears in the gastric juice so that a steady‐state but not equilibrium can presumably be reached with respect to the bath concentration an..