Do Receptors Get Pregnant Too? Adrenergic Receptor Alterations in Human Pregnancy

Abstract

In this review we discuss adrenergic receptor number and function during pregnancy, with emphasis on evidence that pregnancy results in specific receptor alterations from the nonpregnant state. Changes in adrenergic receptor function or distribution in vascular smooth muscle may be in part responsible for the decreased vascular responsiveness seen in human pregnancy, and the lack of the normal alterations may be a part of the syndromes of gestational hypertension, including preeclampsia-eclampsia. The onset of labor may be influenced by adrenergic modulation, and receptor or postreceptor level molecular alterations may trigger or facilitate normal or preterm labor. Human studies are emphasized when possible to assess the role of adrenergic signal transduction regulation in the physiology and pathophysiology of normal and complicated human pregnancy. o 1996 WtIcy-Liss, IIK.

Evidence of dysfunctional β2‐adrenoceptor signal system in pre‐eclampsia

“…Lack of the normal changes in adrenergic receptor function may be part of the pathophysiology of pregnancy‐induced hypertension and pre‐eclampsia 1 . This idea fits with the present observations that showed a reduced total number of β 2 ‐adrenoceptors, but an unchanged fraction of receptors able to bind isoprenaline with high affinity, resulting in a significant reduction in the number of functional receptors.…”

“…Human mononuclear leukocytes have served as an important model for regulation of β 2 ‐adrenoceptors in less accessible tissues 2 , including blood vessels 13 . Thus, the present observation of elevated mononuclear leukocyte receptor densities implies an increased β‐adrenergic sensitivity in smooth vascular muscles and thereby contribute to the reduction in peripheral vascular resistance in normal pregnancy 1 .…”

“…It is possible therefore that the decreased vascular resistance seen in normal human pregnancies is mediated through a progesterone‐dependent increase of β 2 ‐adrenegic tissue sensitivity. On the other hand, failure in the physiological regulation of signal systems, including β 2 ‐adrenoceptor function, may be associated with pregnancy‐induced hypertension and pre‐eclampsia 1 . The present study was performed to determine if functional β 2 ‐adrenoceptors were altered in normal pregnancy and in pregnancies complicated by pre‐eclampsia.…”

“…The mechanisms explaining the vasodilatation of normal pregnancy and the significant vasoconstriction observed in pre‐eclampsia are complex and only partly understood. Many factors are involved, one of which is β 2 ‐adrenoceptor function 1 . Human mononuclear leukocytes were early established as a model for β 2 ‐adrenoceptor studies in clinical investigations 2 .…”

Maternal and Preterm Fetal Sheep Responses to Dexmedetomidine

“…Nonetheless, a number of dexmedetomidine's actions could be of potential benefit to fetuses of parturients requiring heavy sedation, anesthesia, and/or analgesia during pregnancy. 23 One intriguing aspect is the potential for decreased dexmedetomidine-mediated cardiovascular depression in the mother and fetus because of the pregnancy-related decline in systemic maternal α 2 AR sensitivity 24 even as the fetus has increasing numbers of α 2 AR both systemically 25 and centrally. 26 Another intriguing aspect is the possibility that dexmedetomidine can protect the developing brain from excitotoxic injury.…”