Correlation Between Beta- and Alpha-Adrenergic Receptor Concentrations in Human Placenta

Abstract

α₂- and β-adrenergic receptors in human placental membranes have been investigated using the radioligands [³H]-RX 821002 and [³H]-dihydroalprenolol, respectively. The specific binding of the α₂-adrenoceptor antagonist RX 821002 confirms the presence of an α₂-adrenoceptor in the human placenta, which has been characterized previously with [³H]-rauwolscine. The major finding presented here is a correlation between the α₂- and β-adrenergic receptor concentrations (r=0.765) in the human placenta at term. It is suggested that the α₂/β adrenoceptor balance may play an important role in regulation of the vascular bed of the placenta. Determination of the α₂/β ratio may help towards an understanding of the contractility of the placental vascular muscles.