Decidual prolactin (PRL)-releasing factor stimulates the synthesis of PRL from human decidual cells.
Previous studies from our laboratory demonstrated that the acute release of PRL from human decidual tissue is stimulated by a 23.5 kilodalton placental protein which we designated decidual PRL-releasing factor (PRL-RF). To determine whether PRL-RF may also affect the synthesis of PRL and/or cause a secondary increase in PRL release, we have examined the effects of purified PRL-RF on the synthesis and release of PRL over a 96-h period. Exposure of dispersed decidual cells to PRL-RF (0.5 microgram/ml) stimulated a biphasic increase in PRL release with acute transient stimulation during the first 0.5 h and a delayed and sustained stimulation beginning about 8 h after exposure which persisted for the duration of the 96 h. The amounts of PRL released from PRL-RF-exposed cells after 0.5, 8, 12, 24, and 96 h were 321.2 +/- 36.2 (mean +/- SEM, n = 3), 110.2 +/- 5.3, 138.2 +/- 7.2, 194.5 +/- 11.2, and 201.5 +/- 14.2% that of control cells. Studies of the de novo synthesis of [35S]methionyl PRL indicated that the increase in PRL release after the first few hours of exposure to PRL-RF was secondary to an increase in PRL synthesis. Somatostatin (100 nM) inhibited the acute stimulatory effect of PRL-RF, but had no effect on the delayed stimulation of PRL release. On the other hand, cycloheximide (20 microM) completely inhibited the secondary increase in PRL release in response to PRL-RF but had no effect on the acute release. These results demonstrate that PRL-RF stimulates both the synthesis and release of decidual PRL.
D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003656:Decidua / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D007700:Kinetics; D011247:Pregnancy; D011388:Prolactin / Q000096:biosynthesis / Q000378:metabolism*; D014176:Protein Biosynthesis; D012016:Reference Values; D013004:Somatostatin / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000502:physiology*
D013004:Somatostatin; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D003513:Cycloheximide