A new concept of the significance of regional distribution of prostaglandin H synthase 2 throughout the uterus during late pregnancy: Investigations in a baboon model
Wx. Wu et al., A new concept of the significance of regional distribution of prostaglandin H synthase 2 throughout the uterus during late pregnancy: Investigations in a baboon model, AM J OBST G, 183(5), 2000, pp. 1287-1295
OBJECTIVE: We sought to identify regional differences in prostaglandin H sy
nthase 2 messenger ribonucleic acid expressions in various intrauterine tis
sues in the pregnant baboon as an indicator of prostaglandin production cap
ability to explain the various interactive roles of different intrauterine
tissues in the processes that precede, promote, and complete labor.
STUDY DESIGN: Prostaglandin H synthase 2 messenger ribonucleic acid express
ion was measured by reverse transcriptase-polymerase chain reaction or Nort
hern blot analysis in the uterine fundus, lower uterine segment, cervix, am
nion, chorion, and placenta during late pregnancy and spontaneous term labo
r in the pregnant baboon. Myometrial electromyography enabled clear relatio
n of the findings to uterine contractile activity.
RESULTS: There were dramatic increases of prostaglandin H synthase 2 messen
ger ribonucleic acid expressions during late gestation and during labor in
the lower uterine segment, cervix, and decidua. The amniotic prostaglandin
H synthase 2 messenger ribonucleic acid expression increased during labor.
In contrast, the prostaglandin H synthase 2 messenger ribonucleic acid expr
essions in the uterine fundus, chorion, and placenta did not change during
late gestation and labor.
CONCLUSION: Demonstrated increased lower uterine segment and cervical prost
aglandin H synthase 2 abundances would promote lower uterine segment elonga
tion and cervical effacement. Engagement of the fetal presenting part would
stimulate local prostaglandin H synthase 2 expression and obstruct diffusi
on of high forebag prostaglandin to the rest of the uterus, as reported pre
viously in human pregnancy. These data support a new conceptual mechanistic
framework for preparatory changes in the lower uterine segment and cervix
preceding labor as precisely related to myometrial contractility changes.