Directional secretion of prostaglandin F(2alpha) by polarized luminal epithelial cells from pig endometrium

In swine, endometrial prostaglandin F(2alpha) (PGF(2alpha)) is the luteolysin. The capacity of luminal epithelial cells isolated from the endometrium of day 16 cyclic pigs, to secrete PGF(2alpha)500 Omega/cm(2)), they were treated on the apical, basal or both surfaces with 0 or 100 nM oxytocin (OT) in Experiment 1 or phorbol 12-myristate 13-acetate (PMA) in Experiment 2. In the absence of OT or PMA, PGF(2alpha) secretion occurred primarily from the basal surface and was approximately 12-fold greater (P < 0.001) than from the apical surface. Treatment with OT did not stimulate PGF(2alpha) secretion from either surface regardless of which surface was treated. In contrast, PMA increased PGF(2alpha) secretion from both surfaces. Treatment of the apical surface or both surfaces with PMA increased (P < 0.001) PGF(2alpha) secretion similarly from both surfaces. Treatment of only the basal surface with PMA increased (P < 0.01) PGF(2alpha) secretion from both surfaces, but tended (P = 0. 06) to increase its secretion from the basal surface more than from the apical surface. These results indicated that PGF(2alpha) secretion by luminal epithelial cells obtained from cyclic pigs occurs primarily toward a basal direction and is not stimulated by oxytocin. Activation of protein kinase C stimulates directional secretion of PGF(2alpha) from both surfaces of the epithelial cells.