Decreased myometrial β‐adrenoceptors in women receiving β 2 ‐adrenergic tocolytic therapy: Correlation with lymphocyte β‐adrenoceptors

We have determined simultaneously the density of β‐adrenoceptors in human myometria (by (‐)‐[ 125 I]iodopindolol binding) derived from 36 women undergoing cesarean section and in the corresponding circulating lymphocytes (by (‐)‐[ 125 I]iodocyanopindolol binding). In myometrial membranes about 80% to 85% of the β‐adrenoceptors were of the β 2 ‐subtype. The density of myometrial and lymphocyte β‐adrenoceptors in women treated with the β 2 ‐ adrenoceptors agonist hexoprenaline to prevent preterm labor was about 65% to 70% lower than that in nontreated women. Concomitantly, in hexoprenaline‐treated women the 10 µmol/L isoproterenol‐evoked increase in lymphocyte cyclic adenosine monophosphate content (as index for lymphocyte β‐adrenoceptor responsiveness) was diminished to a similar extent. Combining all data resulted in a significant positive correlation between myometrial and lymphocyte β‐adrenoceptor densities ( r = 0.7303; n = 36; p < 0.001). It is possible that determination of β‐adrenoceptor function in circulating lymphocytes may be a useful model to monitor myometrial β‐adrenoceptor changes during tocolytic therapy. Clinical Pharmacology and Therapeutics (1989) 45, 1–8; doi: 10.1038/clpt.1989.1