Glycosaminoglycans in ewe reproductive tracts and their influence on acrosome reactions in bovine spermatozoa in vitro.

Glycosaminoglycans (GAG) promote acrosome reactions (AR) in bovine and rabbit spermatozoa in vitro. Female bovine reproductive tract secretions contained GAG and the concentrations and composition of those GAG varied with different regions and stages of the estrous cycle. This study was designed to evaluate the types of GAG found in reproductive tract secretions of ewes at different stages of the estrous cycle and the ability of the secretions to promote AR. Ewes (n = 48) were slaughtered at 0, 12, 24, 36, 72 and 144 h following observations of standing estrus. Reproductive tracts were flushed with a modified Tyrode's medium (TALP: 7 ml) not containing calcium. Concentrations and composition of GAG in the tract were determined by high performance liquid chromatography. Concentrations of GAG decreased anterior to the cervix: 2.28 to .74 mg/100 mg protein (P less than .05). Increases in heparin-like GAG during the estrual phase and chondroitin sulfate GAG during the luteal phase were noted. Bovine sperm were incubated in tract flushings standardized to contain 4 micrograms/ml of GAG and supplemented with calcium. Sperm incubated in estrual flushings for 9 h exhibited a higher incidence of AR than those incubated in luteal flushings or control, 50% vs 36% and 29%, respectively (P less than .0001). It is concluded that during the estrous cycle there were changes in concentrations and composition of GAG in ewe reproductive tracts and the potencies of those female secretions causing AR varied.