Amniotic membrane production of prostaglandin F2 alpha is reduced in dysfunctional human labor: results of in vivo and in vitro studies.

Mobilization of arachidonic acid from glycerophospholipids and prostaglandin (PG) release from fetal membranes were studied in women with dysfunctional labor in the absence of cephalopelvic disproportion or fetal malposition. Using superfusion of intact amnion and chorion, we found a slight decrease in PGE and a more significant decrease in PGF release by the amniotic side of the fetal membrane obtained from women with dysfunctional labor compared to that in women with normal labor (PGE: normal labor, 2992 pg/cm2.h; dysfunctional labor, 1846 pg/cm2.h; P less than 0.05; PGF: normal labor, 662 pg/cm2.h; dysfunctional labor, 204 pg/cm2.h; P less than 0.02). Release of both prostanoids was significantly greater from the amniotic side in tissues obtained after labor compared to that in prelabor tissue. Analysis of arachidonic acid (by gas liquid chromatography) and phospholipid content (by two-dimensional thin layer chromatography) confirmed metabolic disposal of arachidonic acid from the amnion after the onset of labor. However, no difference in either phospholipid or phospholipase A2-releasable arachidonic acid of individual phospholipid classes was found in amnion tissue from women with normal and dysfunctional labor, suggesting similar activities of phospholipase A2 in these two groups. The finding of decreased free and phospholipase A2-releasable arachidonic acid of the total lipid extract of the amnion of women with dysfunctional labor could suggest further metabolic exhaustion of the substrate or failure of liberation of this fatty acid from glycerophospholipids by enzymes other than phospholipase A2, such as phospholipase C or diacyl and monoacylglycerolipases.