[3H]heparin binding in boar spermatozoa: characterization and correlation with routine semen quality parameters

A simple technique has been established for the purpose of characterizing heparin binding to boar sperm. Binding experiments were performed using [3H]heparin and extended boar semen. [3H]Heparin binding to boar sperm was effectively displaced by increasing concentrations of heparin. [3H]Heparin binding was linear at least between 50,000 and 10(6) spermatozoa and was stable for at least 120 min. Binding was sensitive to fucoidan, chondroitin sulfate B, chondroitin sulfate C, and chondroitin sulfate A, while keratan sulfate had only a marginal effect on binding. The [3H]heparin binding was saturable. Assuming a 13,000 M(r) for the [3H]heparin used, binding to boar spermatozoa showed an apparent equilibrium dissociation constant (Kd) of 23.6 +/- 2.5 nM and a maximum binding capacity (Bmax) of 6.0 +/- 1.1 pmol/10(6) spermatozoa (average values from 6 boars, means +/- SEM). Interejaculate variations in binding parameters were dependent on the male. Thus, with respect to Bmax variation, 4 of 6 boars studied exhibited an interejaculate coefficient of variation of less than 0.33 (0.09, 0.11, 0.11, and 0.29, respectively, for 3 consecutive ejaculates), while in the case of Kd interejaculate variation, only 2 of the 6 boars studied showed acceptable variation coefficients (0.16 and 0.28). No seasonal effect was observed in either of the binding parameters, with the variations following boar-specific patterns. Kd and Bmax intermean differences for different boars during the course of the study period (April-June) were not significant (p > 0.05). Correlations of mean boar binding parameters (Kd and Bmax) with conventional semen quality parameters showed a correlation between Bmax values and those of the osmotic resistance test (r = 0.8990, p < 0.01), normal acrosomes (r = 0.7946, p < 0.05), and bended tails (r = -0.8632, p < 0.02). Kd values were correlated with cytoplasmic distal droplet (r = -0.7992, p < 0.05). The glycosaminoglycans and polysulfated boar sperm binding sites reported in the present work should be regarded as binding sites until further studies elucidate their physiological role. The results obtained suggest that this technique be given a role as a research tool.