Monosaccharide transport across membranes of human spermatozoa. II. Basic properties of D-fructose and D-glucose uptake.

D-glucose uptake by human spermatozoa shows like D-fructose uptake a hyperbolic kinetic. The affinities to the transport system are similar, but the maximal capacity of D-glucose transport is greater than the D-fructose transport. Both transport processes are inhibited by monoiodoacetate. Therefore these transports can be regarded as carrier-mediated active transports. The D-glucose transport moreover is inhibitable by ouabain and is influenced by extracellular Na+. These differences could be the expression that for both monosaccharides different transport systems exist. But the dependence of D-glucose and D-fructose uptake on the extracellular D-fructose-D-glucose-relation permits the conclusion that both systems interact with another.