To evaluate the biosynthesis of prostaglandins in the oviducts, phospholipase A2 (EC 3.1.1.4) activities were first measured in the epithelial cells obtained from rabbit oviducts. At least four kinds of phospholipase A2 (PLA2) activities with respect to calcium dependency and pH requirement were observed. There were two calcium-dependent, pH optima of 7.5 and 8.5 activities, and two calcium-independent, pH optima of 4.0 and 8.0 activities. One of those activities, a calcium-dependent and alkaline active PLA2 activity of the epithelial cells was then compared between the ampullary portion and the isthmic portion of the oviducts. The activity was significantly higher in the ampullary epithelium than in the isthmic epithelium (223.2 +/- 57.2 or 103.8 +/- 32.3 pmol/min/mg, p < 0.05). These results support the idea that the production of prostaglandins, which is dependent upon the activity of the arachidonate cascades, was higher in the ampullary portion of oviduct than that in the isthmic portion. The PLA2 activity of the ampullary epithelium may thus play an important role in the regulation of smooth muscle contractility and ciliary movement.