MODULATION OF POSTTHAW MOTILITY, SURVIVAL, CALCIUM-UPTAKE, AND FERTILITY OF BOVINE SPERM BY MAGNESIUM AND MANGANESE

Because Mg2+ and Mn2+ are potent stimulators of motility through the s timulation of adenylate cyclase activity, the current study was undert aken to modulate the fertilizing ability of bovine semen by incorporat ion of various concentrations of those two salts in extenders before f reezing. Motility analysis at 6 h in vitro showed a positive effect of MgCl2 in a dose-dependent manner from 0.5 to 5 mM (31 to 50%). Mangan ese at the concentration of 0.1 mM also supported good sperm motility (53%) compared with that of the control (28%). Although survival was i ncreased, no detrimental effects were seen on the number of sperm that penetrated mucus of cows in estrus. The intracellular Ca2+ concentrat ion of sperm was very different across treatments after thawing; sperm atozoa that were extended with 2 mM MgCl2 and 0.5 mM MnCl2 possessed t he highest concentrations at thawing. Four hours later, in the presenc e of Ca, spermatozoa that were extended in 0.1 mM MnCl2 showed the hig hest uptake. In the presence of Ca and heparin, spermatozoa that were extended in different amounts of Mg showed Ca2+ concentrations that in creased in a dose-dependent manner. This effect was negated by glucose . Functional fertilizing capacity was also evaluated by in vitro ferti lization, and the different treatments did not show any detrimental ef fects. In summary, 5 mM MgCl2 and 0.1 mM MnCl2 both have beneficial ef fects for the maintenance of sperm motility without detrimental effect s on mucus penetration and fertilizing ability. Furthermore, these tre atments do not prevent subsequent Ca2+ uptake in response to heparin. These in vitro studies are potentially a good sorting system to predic t the benefits of extender modifications.