Heparin and dermatan sulphate induced capacitation of frozen-thawed bull spermatozoa measured by merocyanine-540

Glycosaminoglycans (GAGs) are present in the oviduct in which the major part of sperm capacitation occurs. In this study we have tested how capacitation of frozen-thawed bull spermatozoa is effected by exposure to different GAGs detectable or possibly present in oviductal fluid; i.e. heparin, hyaluronan, heparan sulphate, dermatan sulphate and chondroitin sulphate. Following exposure of different duration, the spermatozoa were stained with either Chlortetracycline (CTC) or merocyanine-540 and evaluated with epifluorescent light microscopy or flow cytometry, respectively. Heparin elicited a significant increase in the number of alive, capacitated spermatozoa, either expressed as higher merocyanine-540 fluorescence (p < 0.0001) or as B-pattern (p = 0.0021) in the CTC assay, during 4 h of incubation. When comparing the different GAG treatments one by one to the negative control in the flow cytometric study, only heparin and dermatan sulphate were significant (p < 0.0001) higher than the control at 0-30 min of incubation. Duration of incubation did not affect the proportion of capacitated spermatozoa when measured as merocyanine-540 fluorescence or CTC B-pattern, but the length of the incubation did affect the number of dead (Yo-PRO 1 positive) spermatozoa (p < 0.0001). Exposure to zona pellucida proteins significantly increased the proportion of acrosome reacted spermatozoa (p = 0.016). Both heparin and dermatan sulphate induce capacitation of frozen-thawed bull spermatozoa in vitro.