SIGNIFICANT DECREASE IN PARATHYROID HORMONE-RELATED PROTEIN CONCENTRATIONS IN AMNIOTIC-FLUID WITH LABOR AT TERM BUT NOT PRETERM

It has been determined whether amniotic fluid concentrations of parath yroid hormone-related protein (PTHrP) change with labour. An evaluatio n of which cells from intrauterine tissues might produce PTHrP has als o been conducted. Amniotic fluid was obtained by amniocentesis from wo men: (1) at term, not in labour; (2) in normal term labour; (3) in pre term labour, undelivered within one week; (4) in preterm labour, deliv ered within one week; (5) in preterm labour associated with clinical c horioamnionitis; and (6) who were gestation-matched controls for chori oamnionitis patients-women in this group were similar to those in Grou p 4 but were different patients. Amnion, chorion, and decidual cells w ere grown by standard techniques and incubated with interleukin-1 beta (IL-1 beta). PTHrP was assayed in duplicate samples of amniotic fluid or tissue culture media using an immunoradiometric assay. There was a significant reduction in amniotic fluid concentrations of PTHrP durin g labour at term. Preterm labour was not associated with significant c hanges in amniotic fluid concentrations of PTHrP although a trend for reduced concentrations was observed. Amnion and chorion produced measu rable quantities of PTHrP and rates of production were increased by tr eatment with IL-1 beta. Decidual cells did not produce detectable amou nts of PTHrP. Hence, labour at term is associated with a decrease in a mniotic fluid PTHrP concentrations that may reflect reduced amnion pro duction, which in turn may play a permissive or active role in the mec hanism(s) of parturition. These data support the view that the mechani sms that control term and preterm labour may be regulated differently.