THE FURTHER METABOLISM OF SORBITOL-3-PHOSPHATE AND FRUCTOSE-3-PHOSPHATE IN THE MATURE RAT LENS

Glucose and phosphorus metabolism in mature (8-month-old) rat lenses w ere examined with NMR spectroscopy. Nondiabetic mature lenses containe d sorbitol-3-phosphate (S3P) and fructose-3-phosphate (F3P) which were absent from young (1- to 2-month-old) normal rat lenses. The concentr ations of these two phosphates can be changed through (1) diabetes ind uction with streptozotocin - this results in a dramatic increase in bo th compounds; and (2) oral dosing with a drug known to prevent sorbito l production - both metabolites disappeared. When normal mature lenses were incubated in 35.5 mM C-13(1)-glucose, both C-13(1)-lactate and C -13(3)-lactate were produced. Preservation of the C-13 label at C-1 is Likely through the formation of C-13(1)-S3P and -F3P, which were then split through an aldolase-like mechanism into two 3-carbon compounds, one an unlabeled glycerol and the other C-13(1)-alpha-glycerophosphat e (from S3P) and C-13(1)-dihydroxyacetone phosphate (from F3P). These reactions can contribute to the increase in alpha-glycerophosphate obs erved in both the streptozotocin-induced diabetic lenses and lenses in cubated in high glucose.