CHORIONIC PROSTAGLANDIN CATABOLISM IS DECREASED IN THE LOWER UTERINE SEGMENT WITH TERM LABOR

We have examined the hypothesis that regional differences in 15-hydrox yprostaglandin dehydrogenase (PGDH) activities occur within the human fetal membranes. Further, we reasoned that a specific reduction in PGD H in the fetal membranes at the lower uterine segment might occur with labour, providing a potential mechanism for local generation of prima ry prostaglandins (PG) that could contribute to cervical ripening. Ful l-thickness membranes were obtained from patients at caesarean section in the presence or absence of labour. Membranes were sampled from thr ee regions: close to the site of placental attachment, in the region o f the internal cervical os, and from a 'middle' area between these two . PGDH activities (sum of PGF(2 alpha) to 15-keto PGF(2 alpha) and 13, 14-dihydro 15-keto PGF(2 alpha) conversion) and immunoreactivity vari ed appreciably between the three regions. PGDH activity was highest in chorion in the cervical region of patients not in labour, but was sig nificantly lower in the chorion from membranes taken closest to the in ternal os of patients in labour. Loss of PGDH activity was not attribu table to a diminution in the number of trophoblast cells in this area. We conclude that regional loss of PGDH in the fetal membranes (chorio n) at the lower uterine segment occurs with labour. Reduced PG catabol ism could facilitate local generation of bioactive PG at this site for cervical effacement. (C) 1997 W. B. Saunders Company Ltd.