Is the attenuation of β-adrenergic agonist efficacy during labor caused by elevated prostaglandin E levels?, , ,

Objective: Our purpose was to investigate whether attenuation of β-adrenergic agonist efficacy during labor is due to elevated prostaglandin E levels. Study Design: β-Receptor function (response to β-agonist or forskolin) was tested in mononuclear leukocytes collected from women at term before or during labor. β-Receptor function was also tested in mononuclear leukocytes of nonlaboring patients after in vitro incubation with oxytocin (1 μmol/L), prostaglandin E2 (10 μmol/L), prostaglandin F2α (10 μmol/L), or buffer alone. Results: Mononuclear leukocytes from women in active labor exhibited a significant attenuation of β-adrenergic receptor function as a result of reduced adenylyl cyclase activity. This effect could be induced in mononuclear leukocytes from nonlaboring women by preincubation with prostaglandin E but not oxytocin or prostaglandin F. Conclusions: Prostaglandin E induces heterologous desensitization of the β-adrenergic receptor system in mononuclear leukocytes, comparable to that seen during labor. We speculate that during labor the elevated levels of prostaglandin E may induce similar effects on the myometrium, thereby decreasing the efficacy of β-agonists as tocolytics. (Am J Obstet Gynecol 1998;179:1168-74.)