Regulation of glutamine metabolism in vitro by bicarbonate ion and pH

The effect of variations of medium pH and bicarbonate concentration on glutamine oxidation was studied in slices and mitochondria from dog renal cortex. Decreasing pH and bicarbonate concentration increased the rate of oxidation of glutamine-U-14C to 14CO2 in both slices and mitochondria, an effect comparable to the acute stimulation of glutamine utilization produced by metabolic acidosis. Decreases in the concentration of glutamate and α-ketoglutarate, which accompany metabolic acidosis in the intact animal, also occurred in tissue slices when pH and [HCO3-] were lowered; decrease in α-ketoglutarate but not in glutamate content occurred in mitochondria under these conditions. Study of independent variations of medium pH and [HCO3-] showed that simultaneous changes in both pH and [HCO3-] produced a greater effect on glutamine metabolism than did change in either of these parameters alone.