Tissue-specific ontogenic expression of prostaglandin H synthase 2 in the ovine myometrium, endometrium, and placenta during late gestation and at spontaneous term labor.
OBJECTIVE
The purposes of this study were to determine (1) whether uterine tissues as well as the fetal placenta are involved in the development of prostaglandin-synthesizing capacity associated with impending labor in pregnant sheep and (2) whether the key enzyme of prostaglandin synthesis, prostaglandin H synthase 2, is differentially expressed in the different intrauterine tissues during late gestation and in association with labor.


METHODS
Myometrium, endometrium, and fetal placenta were removed from ewes at 95 days' gestation, (n = 3), 101 to 110 days' gestation (n = 3), 111 to 120 days' gestation (n = 3), 121 to 130 days' gestation (n = 3), 131 to 140 days' gestation (n = 3), and 141 to 145 days' gestation (n = 4) and from ewes in spontaneous term labor at 143 to 147 days' gestation (n = 4). Expressions of prostaglandin H synthase 2 messenger ribonucleic acid and protein were determined by Northern blot and Western blot analyses. Prostaglandin H synthase 2 was localized in the fetal placenta by immunohistochemical means.


RESULTS
Levels of both prostaglandin H synthase 2 messenger ribonucleic acid and protein increased gradually from 115 days' gestation in the fetal placenta and from 131 days' gestation in the endometrium. A further and more significant increase in prostaglandin H synthase 2 concentration occurred in the placenta and endometrium during spontaneous term labor. In contrast, myometrial concentrations of prostaglandin H synthase 2 messenger ribonucleic acid and protein remained at steady basal levels during the course of pregnancy and increased only during labor. Prostaglandin H synthase 2 was localized in the trophoblast cells of the fetal placenta.


CONCLUSIONS
Tissue-specific ontogenic expression of prostaglandin H synthase 2 was observed in myometrium, endometrium, and placenta during late ovine gestation and spontaneous term labor. Fetal placenta and endometrium showed increased expression of prostaglandin H synthase 2 messenger ribonucleic acid and protein during late ovine gestation, whereas myometrial prostaglandin H synthase 2 concentration remained low throughout late gestation. Prostaglandin H synthase 2 concentrations in the myometrium, endometrium, and placenta are all upwardly regulated during labor.
Wu
W X
WX
Laboratory of Pregnancy and Newborn Research, Physiology Department, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA.
Ma
X H
XH
Nathanielsz
P W
PW
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D004717:Endometrium / Q000201:enzymology*; D005260:Female; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D007743:Labor, Obstetric; D009215:Myometrium / Q000201:enzymology*; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000302:isolation & purification; D012756:Sheep
D012333:RNA, Messenger; D011451:Prostaglandin-Endoperoxide Synthases