Sorbitol generation and its inhibition by Sorbinil in the aging normal human and rabbit lens and human diabetic...

Fresh intact human cataracts (derived from patients with mature-onset diabetes mellitus and from nondiabetic patients), normal human lenses between 2 and 71 years old and lenses derived from 1.5- to 5-kg rabbits were incubated in Earle's media containing enriched 13C-glucose (5 and 15 mM). 31P NMR organophosphate profiles were obtained at the start and end of each incubation. Sorbinil was added to one of each pair of selected lenses, both incubated with 13C-glucose. All the lenses were frozen after 4h of incubation and were subsequently assayed by 13C NMR spectroscopy. The results demonstrate significant sorbitol generation only in young lenses which can be inhibited by Sorbinil. None of the older normal and cataractous human lenses or the mature-onset diabetic cataracts were capable of generating measurable sorbitol levels although they all showed active glucose metabolism and their organophosphate profiles demonstrated normal high-energy phosphate levels. Increased sugar phosphate levels were usually found in the mature-onset diabetic cataracts. Although our NMR spectroscopy is only sensitive to 10(-3) M levels, such concentrations of sorbitol are required to exert their osmotic effects. These data indicate that high sorbitol levels can only be generated in young human and rabbit lenses and correlate well with the age-related changes in aldose reductase activity in these lenses.