Expression of two alpha 2-adrenergic receptor subtypes in human placenta: evidence from direct binding studies.
Adrenergic receptors may play an important role for mediating a variety of metabolic and haemodynamic effects of catecholamines including placental blood flow. The alpha-adrenergic receptors of the human placenta were characterized in vitro by the use of [3H]rauwolscine and [3H]prazosin as radioligands. Saturation experiments would suggest that the alpha-adrenoceptors in the human placenta are alpha 2. Comparative binding studies were performed, using recently synthesized compounds (Beecham Pharmaceuticals, UK) selective for alpha 2A (BRL-44408) and alpha 2B (BRL-41992) subtypes. The results indicate that human placenta contains at least two pharmacologically distinct alpha 2-adrenoceptor subtypes with approximately 60 per cent alpha 2A and 40 per cent alpha 2B receptors. In contrast with the pattern of increasing beta-adrenoceptor density, the concentration of alpha 2-adrenoceptors in term placentae is significantly lower than in placentae from the first trimester.
Falkay
G
G
Department of Obstetrics and Gynecology, A. Szent-Györgyi Medical University, Szeged, Hungary.
Kovács
L
L
D000328:Adult; D001667:Binding, Competitive; D003984:Dibenzazepines / Q000378:metabolism; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000378:metabolism; D007211:Indoles / Q000378:metabolism; D054833:Isoindoles; D010920:Placenta / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D011224:Prazosin / Q000378:metabolism; D011247:Pregnancy; D018341:Receptors, Adrenergic, alpha-2 / Q000032:analysis* / Q000145:classification* / Q000378:metabolism; D014316:Tritium; D015016:Yohimbine / Q000378:metabolism
D003984:Dibenzazepines; D007093:Imidazoles; D007211:Indoles; D054833:Isoindoles; D018341:Receptors, Adrenergic, alpha-2; D014316:Tritium; C072126:BRL 41992; D015016:Yohimbine; D011224:Prazosin; C072125:BRL 44408