Cytosolic alpha-glycerophosphate and lactate dehydrogenase in the lung in endotoxin shock

The lung produces lactate aerobically. In endotoxin shock in aerobic production of lactate increases further. We have investigated an enzymic mechanism for the aerobic lactate in the lung. Since an inadequacy of the cytoplasmic hydrogen "shuttle" enzyme alpha-glycerophosphate dehydrogenase (alpha-GPDH) and/or the presence of lactate dehydrogenase (LDH) in excess of alpha-GPDH can cause aerobic formation lactate, we measured alpha-GPDH and LDH in mitochondria-free cytoplasmic fractions of lungs from control and endotoxic shock rats. The shock was induced by an intravenous injection of E coli endotoxin, 16 mg/kg. In lungs of control or endotoxic shock rats, alpha-GPDH was only 10% of the LDH activity. The low absolute levels of alpha-GPDH and the relative deficiency of this enzyme, compared to LDH in the lungs of control and endotoxic shock rats, can potentially contribute to aerobic lactate production.