title: [2 different populations of adrenergic alpha receptors in the splenic capsule in rats].
abstract: Using the contraction of the smooth muscle of rat spleen capsula, studies of the character of the alpha-adrenergic receptors involved in this reaction where performed in vitro. By computer analysis, the flat dose-response curve of noradrenaline shows the presence of two different subpopulations of alpha-receptors, each being responsible for approximately 50% of the maximal overall contraction. The two subpopulations differ roughly one hundred times by their apparent affinity for noradrenaline (pD2 cca 8 and pD2 cca 6). Solely the high-affinity component is competitively antagonized by the alpha 1-blocker prazosin, needs necessarily extracellular Ca2+ for evoking the contraction and is desensitized by previous contact with a high concentration of noradrenaline. Neither of the two components is influenced in its action by calcium-channel blockers nifedipine and verapamil. The needed exogenous calcium thus enters the cell by different routes than by those affected by the mentioned blockers.
authors.affiliation: Farmakologický ústav Lékarské fakulty Univerzity Karlovy, Praha.
authors.forename: R
authors.initials: R
authors.lastname: Foglar
authors.forename: S
authors.initials: S
authors.lastname: Hynie
authors.forename: M
authors.initials: M
authors.lastname: Wenke
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000378:metabolism* / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013154:Spleen / Q000378:metabolism* / Q000502:physiology
chemical_list: D002121:Calcium Channel Blockers; D011942:Receptors, Adrenergic, alpha; D002118:Calcium; D009638:Norepinephrine; D011224:Prazosin
vernacular_title: Dvĕ rozdílné populace adrenergních alpha-receptorů v capsula linenalis krysy.