ASCORBATE AS A SUBSTRATE FOR GLYCOLYSIS OR GLUCONEOGENESIS - EVIDENCEFOR AN INTERORGAN ASCORBATE CYCLE

Ascorbate catabolism was investigated in murine and human cells unable to synthesize ascorbate due to the missing gulonolactone oxidase acti vity. In HepG2 cells the addition of ascorbate or dehydroascorbate res ulted in high glucose production, while human erythrocytes, MCF7 cells and the cellular elements of the murine blood were able to metabolize ascorbate or dehydroascorbate to lactate. The oxidative agent menadio ne stimulated, while the transketolase inhibitor oxythiamine inhibited , the metabolism of dehydroascorbate in each of these three cell types . Our results suggest that ascorbate breakdown through the pentose pho sphate pathway can reach the glycolytic/gluconeogenic route in differe nt cells. In ascorbate synthesizing species the ascorbate-lactate rout e in peripheral cells may form a catabolic branch of an interorgan asc orbate cycle, where hepatocytes are responsible for ascorbate synthesi s. The catabolic part of this cycle using exogenous ascorbate could be demonstrated even in humans cells. (C) 1997 Elsevier Science Inc.