Induction of c-Jun mRNA without changes of estrogen and progesterone receptor expression in myometrium during human labor

To elucidate the endocrine mechanism of human parturition, the expression o f 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) an d in oxytocin-resistant postterm pregnancy (n=3), c-Fos mRNA was detected i n only one myometrial tissue from a woman in labor. The distribution and in tensity of immunostaining for ER and PR were semiquantitatively scored. Dur ing the late pregnancies, no significant difference was seen in the recepto r scores for myometrial ER and PR between the patients who experienced labo r and those who did not. Receptor scores for ER and PR were significantly l ower 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 ass ociated 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.