Different preferences in the utilization of amino acids for glutathione synthesis in cultured neurons and astroglial cells derived from rat brain

The intracellular contents of glutathione in neuron-rich and astroglia-rich primary cultures derived from the brains of embryonal and newborn rats were found to be 23.1+/-3.0 and 31.2+/-6.5 nmol/mg of protein, respectively. Deprivation of amino acids for 4 h reduced the level of glutathione in neuron-rich cultures by 24%. Glutathione was resynthesized on refeeding of cysteine, glutamine, and glycine. A maximal content of glutathione was found 4 h after refeeding, exceeding that of untreated neuron-rich cultures by 84%. Replacement of cysteine by cystine or glutamine by glutamate during the 4 h refeeding period resulted in a lower intracellular amount of glutathione. An increase in the glutathione level of neuron-rich cultures by 76% was found if the culture medium was supplemented with 250 mu M cysteine. However, no such increase occurred if cystine was used instead. In contrast to neuron-rich cultures, astroglia-rich primary cultures restored a maximal content of glutathione if glutamate and cystine were refed after amino acid deprivation. These results demonstrate that cysteine is the limiting compound in the culture medium for glutathione synthesis in neuron-rich cultures and that astroglial cells and neurons in culture have different preferences for uptake and utilization of amino acids for glutathione synthesis.