[Effects of cadmium on protein tyrosine phosphorylation of mouse spermatozoa and the protective role of EGTA].

In this study, we explored the effects of cadmium (Cd) on mouse sperm motility parame-ters, protein tyrosine phosphorylation and the location of tyrosine-phosphorylated targets using computer-assisted sperm analysis (CASA), western blot (WB) and immunofluorescence technique coupled to sperm in vitro culture method, respectively. The results showed sperm motility was inhibi-ted by Cd in a dose-dependent manner and when Cd increased to 1.0 μmol·L-1, sperm motility was inhibited significantly (P<0.05). Simultaneously, protein tyrosine phosphorylation was enhanced by Cd and in particular, the tyrosine phosphorylation of ～55 kDa proteins was greatly promoted when Cd concentrations were greater or equal to 1.0 μmol·L-1 (P<0.05). Importantly, these tyrosine-phosphorylated proteins were mainly localized in the middle piece of mouse sperm. However, when sperm was incubated with 30 μmol·L-1 ethylene glycol tetraacetic acid (EGTA) and 10 μmol·L-1 Cd concurrently, both the tyrosine phosphorylation of ～55 kDa proteins and sperm motility were not changed obviously (P>0.05). These results suggested that Cd may inhibit sperm motility by inducing the tyrosine phosphorylation of ～55 kDa proteins in the middle piece and EGTA could chelate Cd ions to relieve its toxicity. This study demonstrated that Cd induced the tyrosine phosphorylation of a specific subset of proteins and thus decreased sperm motility. Interes-tingly, EGTA acted as an inhibitor to block Cd from entering the sperm, which provided a novel research method for revealing the molecular mechanisms of reproductive toxicity caused by Cd.