Developmental induction of glutaminase in primary cultures of cerebellar granule cells.

Glutaminase mRNA levels increased over 3-fold relative to total RNA, poly(A)+ RNA, and beta-actin mRNA in neonatal rat cerebellar granule cells as the cells differentiated between days 3 and 8 in culture. In contrast, mRNA levels of another glutamate cycle enzyme, glutamine synthetase, remained constant. Glutaminase protein levels increased per cell more than 2-fold between days 3 and 8, and at least 3-fold by day 10 in these cells. The total amount of glutamate per cell increased about 40% during this period. Glutaminase induction paralleled the development of Ca2+-dependent glutamate release, and the formation of neurites, synaptic vesicles, and synapses. The induction of glutaminase in developing granule cells is consistent with a special role for glutaminase in the synthesis of neurotransmitter glutamate.