Metabolites of citric acid cycle, carbohydrate and phosphorus metabolism, and related reactions, redox and phosphorylating states of hepatic tissue, liver mitochondria and cytosol of the pigeon, under normal feeding and natural nocturnal fasting conditions.

1. The metabolite profile of intact pigeon liver differs greatly from that of pigeon liver homogenates or of the isolated perfused pigeon liver. 2. As compared to the rat liver, there are much higher glycerol-3-phosphate, Pi, and malate contents of the pigeon liver, and much lower 6-phosphogluconate, fructose-1,6-diphosphate, phosphoenolpyruvate, ammonium, ATP, and the sum of adenine nucleotides. The other metabolites in livers of both species do not differ significantly. 3. Pigeon liver mitochondria concentrate phosphoenolpyruvate completely, and accumulate lactate against a concentration gradient. There are rather high mitochondrial malate, glutamate, and aspartate, but low mitochondrial alpha-ketoglutarate and adenine nucleotides. 4. Cytosolic Pi concentration is 1,5-fold higher than mitochondrial one in the fed pigeon liver and 4-fold lower than that in the starved liver. Cytosolic phosphorylation potential, and NAD+/NADH and NADP+/NADPH ratios are from 3- to 7-fold lower than those in the rat liver. 5. In contrast to the rat liver, cellular glucose-1-phosphate, glucose-6-phosphate, fructose-1,6-diphosphate, glutamate, alpha-ketoglutarate and aspartate increase in the starved pigeon liver, and glycerol-3-phosphate, phosphoenolpyruvate, Pi, and adenine nucleotides decrease. Cellular and cytosolic phosphorylation potentials rose without any change in cytosolic NAD+/NADH and NADP+/NADPH ratios. 6. It is concluded that pigeon liver differs from mammalian one and therefore it is of special interest for metabolic studies.