Sulphated glycosaminoglycans (S-GAGs) and syndecans in the bovine oviduct

In vivo, bull sperm capacitation seems to occur mainly in the oviduct. Capacitation of bull spermatozoa can be triggered in vitro by exposure to heparin, a heavily sulphated glycosaminoglycan (S-GAG). We determined the concentration of S-GAGs in oviductal fluid from dairy heifers, collected over the course of several oestrous cycles via surgically implanted intraluminal catheters. We also investigated the presence of syndecans, i.e. heparan sulphate proteoglycans, in the bovine oviductal epithelium of Swedish dairy cattle during standing oestrus and the luteal phase of the oestrous cycle, using immunohistochemistry for three different polyclonal antibodies raised against human syndecan-2 and rat syndecan-1 and syndecan-2, respectively. The concentration of S-GAGs in oviductal fluid obtained from the ampullar segment of the oviduct was significantly higher (P = 0.0026) than it was in fluid from the isthmic segment during the functional period, i.e. from prooestrus to metaoestrus (73.5 ± 10.49 mg/L in ampullar ODF, compared to 43.2 ± 10.74 mg/L in isthmic ODF); least square mean (L.S.M.) ± standard error of the mean (S.E.M.). There was also a significantly higher concentration of S-GAGs in the fluid from the oviduct ipsilateral to the ovulation side 73.5 ± 10.54 mg/L on the ovulation side, compared to 43.1 ± 10.71 mg/L in the oviduct on the contralateral side (L.S.M. ± S.E.M., P = 0.0026) during this period. Both syndecan-1 and syndecan-2 were present in the epithelial cells lining all studied segments of the bovine oviduct, i.e. the UTJ, isthmus and ampulla, during both standing oestrus and dioestrus. The syndecans and S-GAGs found may influence the gametes, while they reside in the oviduct; the amounts of S-GAGs found in the bovine oviduct seem sufficient to act as capacitating factors in vivo.