title: A dual action of histamine on isolated human pulmonary arteries.
abstract: Isometric tension changes in 22 isolated segmental human pulmonary arteries obtained from 17 patients at thoracic surgery were studied after histamine challenge. Cumulative dose-response contraction curves were constructed. A slight potentiation could be found with the H2 antagonist cimetidine, whereas the H1 blocker mepyramine moved the log dose-response curve for histamine to the right indicating competitive antagonism at specific receptors. When mepyramine was added after maximal contraction with histamine, a relaxation occurred that could be blocked by adding cimetidine prior to mepyramine. The in vitro tests reveal a dual action of histamine with a dominating H1 receptor mediated contraction, but with the possibility of relaxation via specific H2 receptors in human pulmonary arteries.
mesh_terms: D002927:Cimetidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006632:Histamine / Q000494:pharmacology*; D006633:Histamine Antagonists; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009129:Muscle Tonus / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D011651:Pulmonary Artery / Q000502:physiology*; D011738:Pyrilamine / Q000494:pharmacology; D011969:Receptors, Histamine H1 / Q000502:physiology; D011970:Receptors, Histamine H2 / Q000502:physiology
chemical_list: D006633:Histamine Antagonists; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D002927:Cimetidine; D006632:Histamine; D011738:Pyrilamine