Partial purification and characterisation of two compounds from amniotic fluid which inhibit phospholipase activity in human endometrial cells.

Two inhibitors of PGF synthesis in human endometrial cells were found in amniotic fluid from term non-labouring patients. Both inhibitors at 10(-9)M reduced the amount of arachidonic acid released from the cells but had no effect on PGF synthesis stimulated by arachidonic acid. The molecular weights were 150-165,000 and 70-80,000 daltons as estimated from gel filtration in two systems. Both compounds precipitated with ammonium sulfate, appeared thermostable and lost activity with trypsin digestion. Both inhibited phospholipase activity and had identical retention times with HPLC. We conclude that the compounds are novel endogenous proteins which inhibit endometrial cell phospholipase.