The influence of the cryopreserving process on rubidium uptake by human spermatozoa

The effect of cryopreservation and its phases on the netto-Rb+ uptake (analogous to the K+ uptake) of washed human spermatozoa was investigated under different conditions. The Rb+ uptake reached a steady state after almost 50-min incubation both before and after the cryopreserving process. The Rb+ uptake could be reduced to about 30% by ouabain and to about 80% by monoiodoacetate. The cryoprotective agents glycerol (G), ethylene glycol (EG), and particularly dimethylsulfoxide (DMSO) reduced the Rb+ uptake by a factor dependent on its concentration. The comparative cryopreservation with G, EG, DMSO,and dimethylformamide (DMFA) as cryoprotective agents caused an inhibition especially of the ouabain-sensitive netto-Rb+ uptake. This inhibitory effect became stronger from G to EG and from DMSO to DMFA. Within the course of cryopreservation especially the process of pelletation, Rb+ uptake was reduced, whereas the prolongation of the equilibration time up to 180 min moderated the effect of the cryopreservation on the Rb+ uptake. Beside the reduction of the absolute Rb+ uptake, the cryopreservation altered the dependence of the netto-Rb+ uptake on the extracellular Rb+ concentration in a sigmoid manner.