Inhibition of the ATP-induced reactivation of demembranated hamster spermatozoa by the action of free ATP4- and MgATP2-.

Abstract

Hamster spermatozoa collected from the caput and cauda epididymidis were washed, diluted in a medium containing Triton X-100 to dissolve the cell membrane and reactivated with various concentrations of MgSO4 and ATP. Stepwise increase in the concentrations of free ATP4- from 0.08 to 1.1 mM at constant concentrations of MgATP2- caused a dose-dependent delay of reactivation but the maximal percentage of motile spermatozoa was inhibited only at 1.1 mM. The inhibitory effect on caput spermatozoa was greater than that on cauda spermatozoa. When concentrations of ATP4- were fixed at 0.2 mM, 2.9 mM-MgATP2- suppressed the reactivation of cauda spermatozoa. When compared to 0.9 mM-MgATP2-, reactivation of caput spermatozoa was delayed at 1.9 mM and almost completely blocked by 2.9 mM-MgATP2-. Inhibition of cauda sperm reactivation by ATP4- and MgATP2- were both prevented by the presence of trypsin (50 ng/ml). Incubation of cauda spermatozoa in the reactivation medium for 1 and 2 min before the addition of ATP progressively reduced the inhibitory effect of ATP4-; inhibition by MgATP2- was reduced to a lesser extent. Addition of 100 microM-cyclic AMP to the medium abolished the delay of reactivation by ATP4- but not that by MgATP2-. Before reactivation occurred, inhibitory concentrations of ATP4- and MgATP2- both induced large-angle coiling of sperm tails but in opposite direction to each other with reference to the asymmetric sperm head. The results suggest that free-ATP4- and superoptimal concentrations of MgATP2- inhibit flagellar movement by different mechanisms.