Pyruvate metabolism in mammalian liver.

PARLI, C. JOHN, LINDA C. BURNS, SHARADCHANDRA K. MEGHAL, KEITH KINNEBERG, ROBERT M. OWEAL, AND ROGER E. KOEPPE. Pyruvate metabolism in mammalian liver. Am. J. Physiol. 216(6) : 1525-l 533. 1969.-Labeling patterns were determined in I) liver and carcass protein glutamate of glucocorticoid-treated rats and fed or fasted rats, mice, rabbits, hamsters, and guinea pigs from pyruvate-Z-14C; 2) free liver glutamate and aspartate after injection of pyruvate-2-14C to fed or fasted rats and to normal fed rats treated with glucagon, mannoheptulose, alloxan, hydrocortisone, or phloridzin; and 3) free glutamate and aspartate following pyruvate-1 -14C or butyrateI-14C injection to fed or fasted rats. The incorporation of 14C into blood glucose was measured in part 2 tion by liver mitochondria from fed or above. fasted Pyruvate oxidarats was assayed by three methods. In all experiments in vivo, fasting dramatically lowers the labeling in C-5 of glutamate when pyruvate-Z14C is given. The administration of mannoheptulose, hydrocortisone (for 5 days), or phloridzin markedly increased liver gluconeogenesis where glucagon, alloxan, or hydrocortisone (single dose) had little effect. An inverse correlation exists between the percentage of labeling in C-5 of free liver glutamate and the net incorporation of 14C into blood glucose from pyruvate-2-14C. Liver mitochondria from fed rats oxidize pyruvate at a significantly faster rate than do those from fasted rats.