OPPOSITE EFFECTS OF POLYAMINES ON GLUTAMATE DEAMINATION IN ISOLATED RENAL TUBULES AND PERMEABILIZED KIDNEY CORTEX MITOCHONDRIA OF RABBIT

The effect of polyamines on glutamate deamination has been studied in both isolated tubules and permeabilized kidney cortex mitochondria of rabbit. Spermine, spermidine and putrescine resulted in a decrease of ammonium release in isolated renal tubules incubated with glutamate in the presence of MSO and AOA inhibitors of glutamine synthetase and am inotransferases, respectively. This was not due to the inhibition of g lutamate transport across renal tubular membranes since transport of [ C-14]glutamate into brush border membranes vesicles was not decreased by polyamines. In contrast, polyamines stimulated glutamate deaminatio n in permeabilized mitochondria. This effect was additive to the actio n of ADP, an allosteric activator of glutamate dehydrogenase. Since th ese compounds decreased both glutamate-induced mitochondrial swelling as well as [C-14]glutamate accumulation in mitochondria, the inhibitor y effect of polyamines on glutamate deamination in renal tubules might be due to a diminished glutamate transport across the mitochondrial m embrane.