The metabolism of l-[3-3h]lactate by isolated hamster liver cells

The rate of tritium removal from L-[3-3H]lactate by hamster liver cells is faster than the analytical rate of lactate utilization, or the rate of 14C disappearance from 6-[U-14C, 3-3H]Llactate decrease. However, addition of low concentrations (0.1 to 1.0 mM) of L-cycloserine, a glutamate pyruvate transaminase inhibitor, nearly equalizes the rates of isotope utilization from L-[3-3H]lactate and L-[U-14C]lactate. The results suggest a very limited rate of recycling of phosphoenolpyruvate back to pyruvate during gluconeogenesis from lactate in fasted hamster liver cells.