Such antagonist compounds may be selected from a class of diacid-containing benzimidazole compounds, that is, compounds having an acidic group attached at the benzimidazole 2-ring position and having an acid group attached at one of the benzimidazole 4-, 5-, 6- or 7-ring positions, as defined by Formula I: ##STR2## wherein each of A and B is a moiety independently selected from carboxylic acid, te