A mode of action of hypertonic saline in inducing abortion

Human decidua and uterine contractility

Physiological saline solution injected into the uterus by the extraamniotic route was found to damage the decidua and rupture its lysosomes. The mechanism by which this procedure provokes abortion may be through the release of lysosomal phospholipase A2 (EC 3.1.1.4), an enzyme thought to regulate the formation of polyunsaturated fatty acids utilized for prostaglandin synthesis. A similar sequence of events may be involved in the initiation of spontaneous labour, since decidual cells obtained at elective Caesarean section at term exhibited degenerative changes and signs of release of a lysosomal marker enzyme. The cause of this release is unknown.

The mechanism of midtrimester abortion induced by intra-amniotic instillation of hypertonic saline: a modification of Gustavii's lysosomal hypothesis

This modification of Gustavii's hypothesis recognizes the central role of saline-induced decidual cell necrosis and secondary prostaglandin release in the initiation of myometrial activity. In the absence of significant necrosis in the decidua basalis, passive stretching of the subplacental myometrium is considered to activate this region leading to secondary intervillous stasis and the reduction in progesterone delivery to the myometrium and systemic circulation. This drop in progesterone further sensitizes the myometrium to PGF2alpha stimulation and helps the self-sustaining process of myometrial activity culminating in clinical abortion. A third hypothetical contributing factor may be the loss of some myometrial inhibitor normally present in the amniotic fluid.