Spermatozoa stimulate prostaglandin synthesis and secretion in bovine oviductal epithelial cells

The dynamic action of oviductal secretory compounds on spermatozoa function is well documented. In contrast, the effect of spermatozoa on oviductal function remains poorly characterized. Previously, our lab and others have shown that prostaglandin (PG), together with other vasoactive peptides, plays major roles in oviductal contractions and sperm transport. We therefore examined the effect of spermatozoa on the production of PG by cow oviductal epithelial cells (OEC). A bovine spermatozoa-OEC co-culture system was utilized for this purpose. OECs in the second passage were co-cultured for 0, 1, 3, 6, 12, and 24 h with six doses of motile, killed, or truncated spermatozoa heads (control; without spermatozoa, 10(2)-10(6) spermatozoa/ml medium). The levels of PGE(2) and PGF(2alpha) in the medium were measured using enzyme immunoassays. Messenger RNA expression of cyclooxygenase-2, PGF synthase (PGFS), and PGE synthase (PGES) was investigated using real-time RT-PCR. The results indicated that motile spermatozoa increased the secretion of PG by OEC as well as cellular expression of mRNA for cyclooxygenase, PGES, and PGFS in a dose- and time-dependent manner. A maximum three- to fivefold increased secretion of PG was observed with a dose of 10(5) spermatozoa/ml after a 12-h co-incubation. Neither killed spermatozoa nor truncated spermatozoa heads stimulated oviductal biosynthesis and secretion of PG at any dose or time point observed. The results provide the first evidence that live spermatozoa in the oviduct up-regulate the local PG system, and thereby, enhance oviductal contractions. Thus, spermatozoa may bear a role in accelerating their own transport into the fertilization site.