S. Gyomorey et al., Fetal-to-maternal progression of prostaglandin H-2 synthase-2 expression in ovine intrauterine tissues during the course of labor, BIOL REPROD, 62(3), 2000, pp. 797-805
We examined whether spontaneous parturition in sheep was associated with ti
ssue-specific changes in prostaglandin H-2 synthase-2 (PGHS-2) expression a
nd/or with altered expression of myometrial EP and FP receptors, Placental
and uterine tissues were collected from three groups of chronically cathete
rized sheep in relation to term spontaneous labor: late pregnancy, not in l
abor; early labor; and active labor. Expression of PGHS-2 mRNA and protein
was determined by in situ hybridization, Western blotting, and immunohistoc
hemistry. Semiquantitative reverse transcription-polymerase chain reaction
was used to assess the presence of and changes in prostaglandin (PG) recept
or subtypes. In placenta, PGHS-2 mRNA and protein localized to trophoblast
uninucleate cells and tended to increase with early labor. PGHS-2 mRNA and
protein localized to endometrial epithelium and to myometrium, where PGHS-2
protein levels rose in active labor tissues, Concentrations of PGE(2) in f
etal plasma rose progressively with labor, whereas 13,14-dihydro-15-keto-PG
F(2 alpha) in maternal plasma increased significantly only in active labor.
Messenger RNA encoding four EP receptor subtypes and FP receptor were pres
ent: in myometrium, but levels did not change with labor, We suggest that s
pontaneous labor in sheep is associated with a progressive increase in PGHS
-2 expression in a temporal and tissue-specific manner from trophoblast to
maternal tissues, rather than alteration in PG receptor gene expression.