Release of Lysosomal Acid Phosphatase Into the Cytoplasm of Decidual Cells Before the Onset of Labour in Humans

Summary In order to elucidate the mechanism triggering the onset of spontaneous labour, decidual cells obtained at elective Caesarean section at term were studied histologically and cytochemically. Although some of the cells were well preserved, many of them showed degenerative changes and signs of release of the lysosomal marker enzyme acid phosphatase into the cytoplasm indicating lysosomal labilization. Since human decidua contains Iysosomal phospholipase A, an enzyme which specifically removes prostaglandin precursor acids from tissue phospholipids and thereby provides substrate for prostaglandin synthesis, the lysosomal labilization might be of significance in the initiation of labour. It is suggested that this labilization is induced by altered levels of sex steroids.