β-Adrenoceptor Function of Leukocytes in Pregnant Women Treated with Terbutaline for Preterm Labor

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Abstract
The correlation between cyclic AMP (cAMP) production in myometrial tissue and that in leukocytes was studied in 21 women delivered by cesarean section for obstetrical reasons. After in vitro β-adrenoceptor stimulation, cAMP production in myometrial tissue was found to be closely correlated with that in leukocytes (r = 0.96). Using cAMP production in leukocytes as an indicator of the state of the β receptor function in myometrium, 18 women treated with terbutaline for preterm labor were studied. Repeat analyses of cAMP production were made in leukocytes before, during and after treatment. The results showed a significant reduction in cAMP production 3-5 hours and 1-2 days after terbutaline infusion. The cAMP values remained low during infusion. In women orally treated with terbutaline, a slight reduction in cAMP production was found after the first dose, but there was no significant reduction after 1-14 days of treatment. After cessation of terbutaline treatment, cAMP production remained low during the following 3 days, but after 5-8 days an increase was found in 7 out of 9 patients. It is suggested that a desensiti-zation of the β-adrenoceptor system in leukocytes appears after β-adrenoceptor agonist treatment in high doses and that measurement of cAMP production reflects the state of desensitization of the β-adrenoceptors in myometrial cells too.