Phospholipase A activity in human and ovine uterine tissues.

Phospholipase A was assayed in crude lysosomal fractions of human decidua, amnion, chorion and myometrium. Activity was present in all the tissues and was highest in decidua and amnion which contained enzymes with pH optima of 6.5-8.0 and 7.2 respectively. Comparison of the activities in tissues obtained before labor with others obtained during labor showed no differences. In sheep, the fetal membranes contained a greater activity of phospholipase A than placenta and myometrium. Stimulation of the fetal adrenals with corticotrophin caused a marked increase in activity in both amnion and chorioallantois. It is concluded that the human amnion and the ovine amnion and chorioallantois could participate in the biosynthesis of prostaglandins by releasing stored arachidonic acid.