Reduced expression of immunoreactive beta2-adrenergic receptor protein in human myometrium with labor.
A considerable body of evidence exists suggesting that the beta(2)-adrenergic receptor (beta(2)-AR) mediates uterine relaxation. However, little information exists on the localization, distribution, or expression of beta(2)-ARs in the human myometrium during the nonpregnant to labor transition. We have used immunochemical methods to investigate beta(2)-AR localization and expression in the nonpregnant, term pregnant, and term parturient uterus. Myometrial biopsies were obtained from 1) nonpregnant, menstruating women undergoing hysterectomy; 2) singleton term pregnant women undergoing elective cesarean section before the onset of labor; or 3) singleton term pregnant women undergoing emergency cesarean section after spontaneous labor. Tissues were processed for immunohistochemistry, immunofluorescence, and Western blotting and a primary polyclonal antibody specific to the human beta(2)-AR to identify immunoreactive myometrial beta(2)-AR. Protein levels were subsequently quantified by densitometry relative to rat brain protein. Immunohistochemistry and immunofluorescence demonstrated the presence of beta(2)-AR predominantly at the plasma membrane and also in the cytosol of myometrial cells. A 2-fold decrease in protein levels of the beta(2)-AR was apparent in the myometrium of labor compared with that of nonpregnant and pregnant nonlaboring women (P < 0.05). These results demonstrate that down-regulation of beta(2)-AR protein with labor may constitute a contributory mechanism by which uterine quiescence is removed at term.
Chanrachakul
Boonsri
B
Academic Division of Obstetrics and Gynecology, Derby City General Hospital, University of Nottingham, Derby, United Kingdom DE22 3NE.
Matharoo-Ball
Balwir
B
Turner
Anita
A
Robinson
Graham
G
Broughton-Pipkin
Fiona
F
Arulkumaran
Sabaratnam
S
Khan
Raheela N
RN
D000906:Antibodies; D015153:Blotting, Western; D015536:Down-Regulation / Q000502:physiology; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D007743:Labor, Obstetric / Q000378:metabolism*; D009215:Myometrium / Q000378:metabolism*; D011247:Pregnancy; D018343:Receptors, Adrenergic, beta-2 / Q000032:analysis / Q000276:immunology / Q000378:metabolism*
D000906:Antibodies; D018343:Receptors, Adrenergic, beta-2