Abstract
To elucidate the endocrine mechanism of human parturition, the expression of
c-Jun and c-Fos mRNA were examined in relation to estrogen receptor (ER) and
progesterone receptor (PR) in human myometrium. c-Jun mRNA was detected in all
myometrial tissues (n=5) during labor but not before labor (n=5) and in
oxytocin-resistant postterm pregnancy (n=3). c-Fos mRNA was detected in only one
myometrial tissue from a woman in labor. The distribution and intensity of
immunostaining for ER and PR were semiquantitatively scored. During the late
pregnancies, no significant difference was seen in the receptor scores for
myometrial ER and PR between the patients who experienced labor and those who
did not. Receptor scores for ER and PR were significantly lower in postterm
pregnancy than in late pregnancy, regardless of the labor status. These data
suggest that there are no changes in ER and PR in human myometrium during
parturition. On the other hand, postterm pregnancy is associated with low ER and
PR. c-Jun, induced during labor without changes in ER and PR, may play a role as
a signaling mechanism in human myometrium.