Decreased myometrial β-adrenoceptors in women receiving β2-adrenergic tocolytic therapy: Correlation with lymphocyte β-adrenoceptors

Abstract

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