Metabolism of Round Spermatids: A Possible Regulation of Hexose Transport

Round spermatids (steps 1–8) were isolated from rat testes and glucose transport into the cells was examined. The exposure of spermatids to glucose resulted in an extremely low level of ATP. In contrast, the level of ATP remained constant in the presence of pyruvate. Transport of a glucose analogue, 2‐deoxy‐D‐[ 3 H]glucose ([ 3 H]dGlc) into spermatids was correlated with intracellular levels of ATP and was much greater in cells with higher rather than lower levels of ATP. [ 3 H]dGlc transport into spermatids with low levels of ATP was partially reversed when the cells were incubated with pyruvate. Inhibition of [ 3 H]dGlc transport was exerted on Vmax and not on Km. Moreover, glucose acted as a competitive inhibitor of [ 3 H]dGlc uptake (Km increased; Vmax unaltered). These results suggest that glucose transport into spermatids is active in vitro and probably regulated by the intracellular level of ATP.