Pulmonary and placental 15-hydroxyprostaglandin dehydrogenase in rat during pregnancy

15-Hydroxyprostaglandin dehydrogenase (PGDH) in rat lung and placenta during pregnancy was examined using a photometric assay. Pulmonary PGDH activity varied slightly during pregnancy, being significantly higher on days 10 and 19 of gestation than on day 22. Placental PGDH activity changed strikingly according to the day of pregnancy. Activity was relatively high on day 10 of gestation, fell to a low level on day 15, then increased to a maximum on day 22. A rapid fall in pulmonary PGDH activity and a remarkable increase of placental PGDH activity occurred on the day just before parturition. The results suggest that pulmonary and placental PGDH activity may cooperatively contribute to the continuity of pregnancy, and the process of parturition.