Ascorbic acid synthesis and breakdown were investigated in isolated he
patocytes prepared from fasted mice, Stimulation of gluconeogenesis by
alanine or xylitol led to ascorbate synthesis, On the other hand, asc
orbate or dehydroascorbate addition resulted in concentration-dependen
t glucose production and elevation of the pentose phosphate pathway in
termediate xylulose 5-phosphate. Stimulation of ascorbate oxidation an
d/or the inhibition of dehydroascorbate reduction increased glucose fo
rmation, Inhibition of the pentose phosphate pathway decreased glucose
production from dehydroascorbate with increased accumulation of xylul
ose 5-phosphate, These results suggest that ascorbate can be recycled
by a novel way involving intermediates of the pentose phosphate pathwa
y, gluconeogenesis and hexuronic acid pathway.