title: Irreversible antagonism of histamine H2 receptors in guinea-pig myocardium.
abstract: Dissociation constants and receptor reserves for histamine acting at H2 receptors in guinea-pig right atria and papillary muscles were measured using the irreversible H2 receptor antagonist L-643,441. Histamine alone was less potent in papillary muscles than in right atria, and maximum responses of papillary muscles to histamine were more susceptible to depression by L-643,441 than were maximum responses of right atria. However, dissociation constants (-log KA values) for histamine calculated using 3 different doses of L-643,441 were 0.5 log unit greater in papillary muscles than in right atria. A more marked difference was found in the estimates of receptor reserve for histamine, which appeared to be much greater in right atria than papillary muscles.
authors.forename: K M
authors.initials: KM
authors.lastname: MacLeod
authors.forename: D
authors.initials: D
authors.lastname: Wenkstern
authors.forename: J H
authors.initials: JH
authors.lastname: McNeill
mesh_terms: D000818:Animals; D005260:Female; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D010210:Papillary Muscles / Q000378:metabolism; D011968:Receptors, Histamine / Q000187:drug effects*; D011970:Receptors, Histamine H2 / Q000187:drug effects*; D013830:Thiadiazoles / Q000494:pharmacology*
chemical_list: D006635:Histamine H2 Antagonists; D011968:Receptors, Histamine; D011970:Receptors, Histamine H2; D013830:Thiadiazoles; C037400:L 643441; D006632:Histamine