Protons and glucose metabolism in shock.

When oxygen is limiting, animals can ferment glucose via several metabolic pathways varying in energetic efficiency and leading to various end products (such as lactate, succinate, or propionate). Because the pH dependence of H+ production by fermentation is opposite to that by hydrolysis of adenosine triphosphate formed in the fermentation, the total number of moles of protons generated is always two per mole of fermentable substrate. However, two and three times more adenosine triphosphate can be turned over per mole of protons produced in succinate and propionate fermentations, respectively, than in lactate fermentation. At its limit, this advantage would achieve the same balance between H+ production and H+ consumption during ATP cycling that is observed in aerobic metabolism, a situation observed in certain alcohol fermentations. Since proton balance during anaerobiosis is clearly adaptable, we consider possible impact and functions of net H+ accumulation during carbohydrate metabolism in endotoxin shock.