title: Oxytocin and bovine parturition: a steep rise in endometrial oxytocin receptors precedes onset of labor.
abstract: Oxytocin receptors were measured in myometrium and intercaruncular endometrium of cows during pregnancy and parturition. Concentrations of estradiol-17 beta, estrone, and progesterone in peripheral blood were also measured. Receptor concentrations in the endometrium rose almost 200-fold from Day 20 to term (p < 0.0001, ANOVA), from 40 +/- 11 to 7300 +/- 1430 fmol/mg protein. Myometrial receptor concentrations increased 10-fold from 180 +/- 36 fmol/mg on Day 20 to 1850 +/- 360 fmol/mg protein at term (p < 0.0001, ANOVA). During labor, endometrial receptors (6600 +/- 1300 fmol/mg) remained at prelabor values, whereas myometrial receptor concentrations had decreased to 1190 +/- 316 fmol/mg (not significant) and declined further postpartum. Plasma concentrations of progesterone declined from 4-5 ng/ml to about 2 ng/ml between Days 250 and 282 and dropped to < 0.2 ng/ml shortly before delivery. Plasma concentrations of estrone and estradiol-17 beta were below 10-20 pg/ml until Day 230. Estrone concentrations were significantly (p < 0.05) increased by Day 250 and estradiol-17 beta by Day 270, and then both rose rapidly. During labor, plasma estrone was 1135 +/- 245 pg/ml and plasma estradiol-17 beta was 226 +/- 131 pg/ml. The molar ratio of estrone and estradiol-17 beta to progesterone rose from less than 0.01 to 4.4 during labor, and was correlated with oxytocin receptor concentrations in endometrium (r = 0.5160, p < 0.001), but not those in myometrium (r = 0.0122). The regulation of oxytocin receptors by ovarian hormones in the two tissues may therefore differ.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Obstetrics and Gynecology, Cornell University Medical College, New York, New York 10021.
authors.forename: A R
authors.initials: AR
authors.lastname: Fuchs
authors.forename: H
authors.initials: H
authors.lastname: Helmer
authors.forename: O
authors.initials: O
authors.lastname: Behrens
authors.forename: H C
authors.initials: HC
authors.lastname: Liu
authors.forename: L
authors.initials: L
authors.lastname: Antonian
authors.forename: S M
authors.initials: SM
authors.lastname: Chang
authors.forename: M J
authors.initials: MJ
authors.lastname: Fields
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D004717:Endometrium / Q000378:metabolism*; D004958:Estradiol / Q000097:blood; D004970:Estrone / Q000097:blood; D005260:Female; D005865:Gestational Age; D007743:Labor, Obstetric / Q000378:metabolism*; D009215:Myometrium / Q000378:metabolism; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D011374:Progesterone / Q000097:blood; D011945:Receptors, Angiotensin / Q000096:biosynthesis*; D018045:Receptors, Oxytocin; D014599:Uterus / Q000378:metabolism
chemical_list: D011945:Receptors, Angiotensin; D018045:Receptors, Oxytocin; D004970:Estrone; D011374:Progesterone; D004958:Estradiol