Decrease in myometrial beta-adrenergic receptors with prenatal cocaine use.
OBJECTIVE
To determine if cocaine use during pregnancy is associated with a reduction in the number or affinity of beta-adrenergic receptors in human myometrium.


METHODS
Myometrium was obtained at cesarean delivery of five women who reported using cocaine during pregnancy and from ten controls. Saturation binding assays were performed on the myometrial membrane fractions using [125I]-cyanopindolol to determine beta-adrenergic receptor concentration and affinity. The percentages of beta 1- and beta 2-adrenergic receptors were determined in three cocaine users and four control patients by performing competition binding assays using the beta 2 antagonist ICI 118,551. Results were compared using unpaired Student t tests.


RESULTS
Women who reported using cocaine during pregnancy had a significantly lower mean (+/- standard deviation) concentration of myometrial beta-adrenergic receptors than did controls (22 +/- 8 versus 52 +/- 23 fmol/mg protein, respectively). There was no difference in the receptor affinity constants between cocaine users and controls (16 +/- 2 pmol/L for both groups). The percentages of beta 1- and beta 2-adrenergic receptors in the myometrium of the cocaine-use group and control group were similar: 86 +/- 1% beta 2 in the cocaine-use group and 83 +/- 7% beta 2 in the control group.


CONCLUSIONS
Cocaine use during pregnancy may be associated with a down-regulation of beta-adrenergic receptors in human myometrium. This could result in a decreased capacity for uterine relaxation and, consequently, a predisposition to preterm labor.
Smith
Y R
YR
Department of Obstetrics and Gynecology, University of Michigan Medical Center, Ann Arbor.
Dombrowski
M P
MP
Leach
K C
KC
Hurd
W W
WW
D000319:Adrenergic beta-Antagonists; D001665:Binding Sites; D001667:Binding, Competitive; D016022:Case-Control Studies; D002585:Cesarean Section; D003042:Cocaine; D005260:Female; D006801:Humans; D009215:Myometrium / Q000378:metabolism*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000378:metabolism*; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D019966:Substance-Related Disorders / Q000378:metabolism*
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; D003042:Cocaine