EFFECT OF MACROMOLECULES FROM OVIDUCTAL CONDITIONED MEDIUM ON BOVINE SPERM MOTION AND CAPACITATION

The effect of macromolecules from oviductal conditioned medium (CM) on sperm motility and capacitation was studied. Sperm peeled from three bulls was incubated in either luteal isthmic CM, luteal ampullary CM, estrual isthmic CM, estrual ampullary CM, or control medium (no CM) fo r 4 h. Sperm capacitation and motility were assessed at 10 min and 4 h . Estrual isthmic CM capacitated significantly more spermatozoa at 4 h than estrual ampullary CM or control medium. CM also affected lateral head movement (ALH) and beat cross-frequency (BCF) of sperm. In a sec ond experiment, the glycosaminoglycan (GAG) content of the different t ypes of oviductal CM was quantified. Estrual isthmic CM contained more GAG than estrual ampullary CM. Among luteal samples, no difference in GAG concentration between the isthmic and ampullary CM was found. Hea t treatment (100 degrees C) of oviductal CM before coincubation with s perm significantly reduced, but did not eliminate, the capacitating ab ility. Because heat treatment denatures proteins and decreases the cap acitating ability of certain GAG, we concluded that the capacitating e ffect of estrual isthmic CM may be associated with proteins, GAG, and proteoglycans in the CM. Isthmic secretions may play a major role duri ng in vivo sperm capacitation, given that bovine spermatozoa may resid e in the oviduct isthmus for up to 18 h before fertilization.