Platelet activating factor increases ciliary activity in the hamster oviduct through epithelial production of prostaglandin E₂

Abstract.

We investigated the signal transduction mechanisms associated with an increase in ciliary beat frequency (CBF) produced by platelet activating factor (PAF) in oviductal ciliated cell cultures. In the range of concentrations similar to that produced by preimplantation embryos, PAF increased the CBF in a dose-dependent manner. The addition of PAF and prostaglandin E₂ (PGE₂) to the cultures produced a synergic increase of ciliary beating, suggesting that PAF and PGE₂ signal transduction pathways may be associated. To demonstrate this hypothesis, cyclooxygenase-2 (COX-2) was selectively blocked by a specific inhibitor, NS-398, and the PAF-induced CBF increase was abolished. Moreover, a phospholipase A2 (PLA₂) inhibitor, AACOCF3, blocks the PAF-induced CBF increase. PGE₂ production by oviductal epithelial cells is stimulated by PAF, and WEB-2086, a PAF-receptor blocker, specifically blocks the PAF-induced PGE₂ production. Using the fluorescent indicator fura-2, we measured the effect of PAF on intracellular Ca²⁺ concentration ([Ca²⁺]_i) in individual ciliated cells. PAF induced a transient increase of [Ca²⁺]_i that was blocked by WEB-2086 or by removal of extracellular Ca²⁺. We propose a mechanism for PAF-mediated signal transduction in the ciliated cells of the oviductal epithelium. Minimal doses of PAF trigger Ca²⁺ mobilization in tandem with increased PLA₂ activity and a COX-2-mediated increase in PGE₂. Local PGE₂ production by the oviductal mucosa suggests the presence of an autocrine loop controlling ciliary activity.