Determination of time-dependent accumulation of d-lactate in the streptozotocin-induced diabetic rat kidney by column-switching HPLC with fluorescence detection

For better understanding the complete metabolism and the physiological role of d-lactate, the concentrations of d-lactate in the serum, liver and kidney of normal and diabetic rats were determined by our established column-switching HPLC method with pre-column fluorescence derivatization. Eight-week-old male Sprague–Dawley rats were administered with streptozotocin (STZ) (80 mg/kg) or citrate buffer intraperitoneally. The tissues were then removed and homogenized after 4, 8, 12 and 16 weeks of drug administration, respectively. The homogenates were centrifuged at 1200 × g for 10 min, then the supernatants were derivatized with a fluorescent reagent, 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ), separated on an ODS column followed by a Chiralpak AD-RH chiral column for enantioseparation. The results showed that the d-lactate content elevated in all the 3 examined tissues under diabetic stages. In addition, d-lactate concentrations in rat kidney were accumulated significantly and time-dependently in diabetic groups after receiving STZ for 4, 8, 12 and 16 weeks (2.99, 13.11, 18.19, 23.23 vs. 0.79 μmol/mg protein as control group). Moreover, the kidney of induced 12-week diabetic rat renal showed some histological changes of progressive diabetic nephropathy. The results suggest that d-lactate may be used as a marker of diabetic nephropathy.