CHANGES IN ESTROGEN-RECEPTOR MESSENGER-RIBONUCLEIC-ACID IN SHEEP FETAL AND MATERNAL TISSUES DURING LATE-GESTATION AND LABOR

OBJECTIVE: Our purpose was to investigate whether there is an increase in messenger ribonucleic acid for estrogen receptor in critical maternal or fetal tissues in the last third of pregnancy and during labor in sheep. STUDY DESIGN: Estrogen receptor messenger ribonucleic acid was measured by Northern hybridization analysis in fetal-placental and maternal uterine tissues during the last third of pregnancy and during spontaneous or cortisol-induced labor in sheep. Statistical differences were assessed with two-way analysis of variance. RESULTS: No estrogen receptor messenger ribonucleic acid was observed in amnion or chorion in any animal studied. There were no gestational age related changes in estrogen receptor messenger ribonucleic acid in any tissues between 100 and 145 days' gestation. During spontaneous and cortisol-induced labor estrogen receptor messenger ribonucleic acid increased significantly (p < 0.05) in myometrium, endometrium, and cervix. No increase was observed in the fetal placental cotyledon and mesometrium. Estrogen receptor messenger ribonucleic acid was markedly decreased (p < 0.05) in myometrium and endometrium after fetal adrenalectomy. CONCLUSION: An increase in estrogen receptor messenger ribonucleic acid in association with labor may contribute part of the mechanism by which estrogens exert their influence on the process of parturition.