Constitutive glucose transport in rat Leydig cells and pyruvate support of steroidogenesis

To facilitate the interpretation of in vitro experiments that use pharmacological agents, such as cytochalasin B, which inhibits glucose transport, an alternative to glucose as an energy source for rat Leydig cells was sought. Pyruvate was superior to glucose as an energy source for the support of steroidogenesis. The concentration of pyruvate required to support half-maximum androgen production was lower than that for glucose (60 +/- 8 versus 478 +/- 87 microM, respectively), and pyruvate supported a higher rate of maximum LH-stimulated androgen production. The latter result suggested that glucose availability can be rate limiting for steroidogenesis in in vitro experiments. The acute regulation of glucose transport was therefore investigated using 2-Deoxy-D-[2,6(3)H]glucose. Uptake of 2-Deoxy-D-[2,6(3)H]glucose by Leydig cells was not affected by insulin, LH, or glucose deprivation, suggesting that it is a constitutive process in these cells.