5-OXOPROLINE AND CARBAMYL ASPARTATE ACCUMULATION IN RAT HEPATOCYTES

When hepatocytes from fasted rats were incubated with glycogenic subst rates, addition of high concentrations of L-alanine produced an accumu lation of 5-oxoproline, as measured by the C-14 yield in the presence of (NaHCO3)-C-14. An oxoprolinase inhibitor doubled the 5-oxoproline a ccumulation, but had no effect on ureagenesis or on the L-alanine stim ulation of glycogenesis. This result suggests that the gamma glutamyl cycle plays no role in L-alanine transport in the liver. When high lev els of L-glutamine and/or NH3 were added to the hepatocytes, considera ble carbamyl aspartate accumulation The effect was increased by L-norv aline and decreased by L-ornithine and low levels of ZnCl2. The increa sed carbamyl aspartate formation appeared to correlate with increased aspartate levels.