CORRELATION BETWEEN BETA-ADRENERGIC AND ALPHA-ADRENERGIC RECEPTOR CONCENTRATIONS IN HUMAN PLACENTA

alpha(2)- and beta-adrenergic receptors in human placental membranes h ave been investigated using the radioligands [H-3]-RX 821002 and [H-3] -dihydroalprenolol, respectively. The specific binding of the alpha(2) -adrenoceptor antagonist RX 821002 confirms the presence of an alpha(2 )-adrenoceptor in the human placenta, which has been characterized pre viously with [H-3]-rauwolscine. The major finding presented here is a correlation between the alpha(2)- and beta-adrenergic receptor concent rations (r=0.765) in the human placenta at term. It is suggested that the alpha(2)/beta adrenoceptor balance may play an important role in r egulation of the vascular bed of the placenta. Determination of the al pha(2)/beta ratio may help towards an understanding of the contractili ty of the placental vascular muscles.