Free amino acids reflect impact of selenite-dependent stress on primary metabolism in rat lens.

PURPOSE

A decrease in phase separation temperature, prior to nuclear cataract, has been correlated with elevated free amino acid content. Hence, we determined how selenite-induced stress alters free amino acid pools in the rat lens, following a single subcutaneous dose of sodium selenite (30 nmol g-1 body weight) in 10- to 14-day-old Sprague Dawley rats.

RESULT

Oxidative stress was evident in lenses 24 h after rats were treated with selenite. Glutathione content was decreased by 60% in the lens cortex and nucleus; the flux of glucose through the pentose phosphate pathway was increased; and glycerol-3-phosphate content was elevated. Amino acid transport, evaluated as 14C-cycloleucine uptake, was not altered, although 14C-glutamine was oxidized at a slower rate. Lenses from treated animals displayed, among the free amino acids, increased glutamine, proline, serine, glycine and the branched chain amino acids, while aspartate, glutamate, and taurine were less.

CONCLUSIONS

A systemic delivery of sodium selenite caused oxidative stress in the rat lens. Direct effects on primary metabolism altered free amino acid pools that may contribute to transient and permanent changes in lens transparency.