Distribution and characteristics of histamine H1-receptors in guinea-pig airways identified by [3H]mepyramine.
The distribution and characteristics of histamine H1-receptors in various regions of guinea-pig airways have been studied using the antagonist [3H]mepyramine. A similar density of specific [3H]mepyramine sites was found in trachea, bronchi and parenchyma and these sites possessed pharmacological properties expected of a histamine H1-receptor. In addition, there was a large component of [3H]mepyramine binding that did not show stereoselectivity towards the isomers of chlorpheniramine and as such cannot be considered to represent binding to an H1-receptor. This non-specific component accounted for approximately 80% of total [3H]mepyramine binding when assays were performed in Tris-HCl buffer but was considerably reduced by the presence of sodium ions in the incubation buffer. The present results do not confirm previous reports on the heterogeneity of histamine H1-receptors in guinea-pig lung and suggest that this may, in part, be due to difficulties in accurately assessing true receptor specific binding.
D000631:Aminopyridines / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008168:Lung / Q000032:analysis*; D008297:Male; D011738:Pyrilamine / Q000378:metabolism*; D011869:Radioligand Assay; D011968:Receptors, Histamine / Q000032:analysis*; D011969:Receptors, Histamine H1 / Q000032:analysis*; D012964:Sodium / Q000494:pharmacology; D014132:Trachea / Q000032:analysis*; D014316:Tritium
D000631:Aminopyridines; D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D014316:Tritium; D012964:Sodium; D011738:Pyrilamine