Short communication Pre-treatment of cattle sperm and/or oocyte with antibody to lipocalin type prostaglandin D synthase inhibits in vitro fertilization and increases sperm-oocyte binding

The present study was conducted to determine the affect of pre-treating of oocytes and/or sperm with a rabbit polyclonal antibody against recombinant cattle lipocalin type prostaglandin D synthase ( L-PGDS) on in vitro sperm–oocyte binding and fertilization. In vitro matured cattle oocytes were incubated (39 ◦ C, 5% CO2 in air) for 1 h in the following treatments either 500L of fertilization medium (FM) or FM with L-PGDS (1:2000). Frozen–thawed spermatozoa were washed by a 45/90% layered Percoll gradient centrifugation and incubated for 1 h either FM or FM with L-PGDS. This study utilized five different treatments: (1) no antibody (control); (2) a rabbit IgG against a non-bovine antigen, bacterial histidase (hist); (3) L-PGDS at fertilization time (with fertilization medium); (4) L-PGDS-treated oocytes; or (5) L-PGDS-treated sperm. Pre-treated oocytes were incubated with 10 × 10 4 washed spermatozoa per 25 oocytes. Oocytes used to assess sperm binding were stained with Hoescht 33342, and the number of sperm bound per zonae pellucidae counted. The remaining oocytes were fixed in acid alcohol, stained with 1% acetate-orcein and observed to determine the presence of pronuclei. More sperm bound to the zonae pellucidae when oocytes and/or sperm were pre-treated with L-PGDS: (1) 26.4 ± 3.0; (2) 25.6 ± 3.0; (3) 59.7 ± 3.0; (4) 56.4 ± 3.0; and (5) 57.1 ± 3.0. Addition of L-PGDS with sperm, oocytes, or both, decreased fertilization (P < 0.05) compared with the control: (1) 89.2 ± 2.0%; (2) 87.5 ± 2.0%; (3) 19.4 ± 2.0%; (4) 27.2 ± 3.1%; and (5) 14.1 ± 3.4%. The L-PGDS reacts with both oocytes and spermatozoa, resulting in