[Closer characterization of alpha-receptor subpopulations in the smooth muscle of the splenic capsule in rats].
Two different subpopulations of adrenergic alpha-receptors -- "high-affinity" (pD2 less than 8) and "low-affinity" (pD2 less than 6) ones -- are involved in alpha-adrenergic contractions of the rat spleen muscle evoked by noradrenaline in vitro. Only the "high-affinity" subpopulation is agonistically influenced by the alpha 1-mimetic phenylephrine (pD2 cca 6, pKA cca 4.8), antagonistically influenced by prazosin (pA2 cca 9); it has a substantial receptor reserve for noradrenaline and a somewhat lower reserve for phenylephrine, it can be desensitized by these mimetics and it requires the presence of exogenous Ca2+ in the medium for evoking the contraction. -- Only the "low-affinity" subpopulation is agonistically influenced by the alpha 2-mimetic UK-14304. Both subpopulations are activated by noradrenaline and competitively blocked by yohimbine. The effect of neither subpopulation is influenced by nifedipine. According to the new classification (11) the "high-affinity" receptors can be described as alpha 1A, the "low-affinity" ones as alpha 2A. Contrarily to current data, the peculiar feature of this second subpopulation is a low affinity for yohimbine (pA2 less than 7) and a certain extent of blockability by phenoxybenzamine.
Foglar
R
R
Farmakologický ústav Lékarské fakulty Univerzity Karlovy, Praha.
Hynie
S
S
Lincová
D
D
Wenke
M
M
D000818:Animals; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000378:metabolism* / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D013154:Spleen / Q000378:metabolism*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D010643:Phenoxybenzamine; D010656:Phenylephrine; D015016:Yohimbine; D009543:Nifedipine; D009638:Norepinephrine
Pokus o blizsí charakteristiku alpha-receptorových supopulací v hladkém svalu krysí capsula lienalis.