IMMUNOHISTOCHEMICAL LOCALIZATION, MESSENGER-RIBONUCLEIC-ACID ABUNDANCE, AND ACTIVITY OF 15-HYDROXYPROSTAGLANDIN DEHYDROGENASE IN PLACENTA AND FETAL MEMBRANES DURING TERM AND PRETERM LABOR

Type 1 15-hydroxyprostaglandin dehydrogenase (PGDH) is the main enzyme responsible for the metabolism of prostaglandin E(2) (PGE(2)) and PGF (2 alpha). To examine the possibility that a deficiency of PGDH might contribute to preterm labor, we measured localization of immunoreactiv e (IR-) PGDH, PGDH mRNA, and PGDH enzyme activity in chorio-decidua, p lacenta, and amnion in patients after term elective cesarean section ( n = 9), after spontaneous vaginal term delivery (n = 10), and at idiop athic preterm labor (PTL) in the absence of infection (<36 weeks gesta tion; n = 11). Localization of IR-PGDH was determined in additional sp ecimens of membranes after PTL with infection (n = 13) and without (n = 37). IR-PGDH was localized in syncytiotrophoblast and intermediate t rophoblasts in placenta and in the trophoblast layer of extraplacental chorion, but was absent from amnion in all patient groups. In chorion , the number of IR-positive trophoblasts was significantly reduced in the idiopathic PTL group compared to those in the other groups. The re lative abundance of PGDH mRNA in the chorio-decidua, but not the place nta, from spontaneous labor and PTL was significantly less than that a fter cesarean section. PGDH mRNA in chorio-decidua from preterm patien ts correlated with PGDH enzyme activity. Undetectable or low IR-PGDH i n chorionic trophoblasts was also associated with low enzyme activity. These results suggest that there exists a subset of patients that pre sent in PTL because of reduced PGDH expression in chorionic trophoblas ts. We suggest that this relative deficiency would allow PGs synthesiz ed in the amnion or chorion to escape metabolism in the chorion and th ereby contribute to the stimulus to idiopathic PTL.