CONVERSION OF ASCORBYL-2-PHOSPHATE TO ASCORBIC-ACID IN RAINBOW-TROUT

Conversion Of L-ascorbyl-2-phosphate (AsP) to L-ascorbic acid (AsA) was investigated in vivo in rainbow trout Oncorhynchus mykiss administered with AsP orally and intraperitoneally. AsP magnesium salt or AsA (each 200 /mumol in 2 g of casein basal diet) was orally administered to each rainbow trout once. The fish were sacrificed at varying intervals during the experimental period, and the plasma AsA concentrations and the amounts of AsP and AsA in the contents of the alimentary canal were measured by high-performance liquid chromatography. There was no statistical difference in the plasma AsA concentration between the AsP-administered group and the AsA-administered group (control). The AsP concentration in the plasma was below detectable levels throughout the experimental period. Most of the AsP administered was hydrolyzed to AsA in the pyloric caeca and intestine but not iii the stomach. AsP magnesium salt (10 mumol) was also administered to rainbow trout (40-70 g) intraperitoneally. AsA concentrations in the plasma, liver, and kidney increased rapidly after the AsP injection. A little AsP was detected in the plasma, liver, and kidney 1 h after the injection; the AsP concentration decreased below detectable levels after 3 h. These findings indicate the ready conversion of AsP to AsA in the rainbow trout body.