Objective: Tubulointerstitial fibrosis plays an essential role in progression to end stage renal disease (ESRD) in various chronic renal failure (CRF) models including the 5/6 nephrectomy (5/6). The present study examines the renoprotective effect of citrate in the renal ablative model that is quite similar to CRF in human.
Material and Method: Male Wistar rats underwent 5/6 and were fed with tap water (5/6tap) or tap water containing 67 mEq/L citrate solution (5/6cit). Sham-operated rats (S) were divided into Stap and Scit groups. Renal function, renal histopathology, renal α-Smooth muscle actin (SMA), and renal transforming growth factor (TGF) - 1 were determined immediately and at the 8th week after operation.
Results: Following the surgery, the values of glomerular filtration rate (GFR) in the 5/6tap and the 5/6cit groups were 2.39 + 0.25 and 2.35 + 0.25 (mL/kg/min), respectively, both were significantly lower than sham groups (p < 0.05). At the eighth week, the 5/6tap group had progressively decreased GFR and had higher fibrosis score, increased α-SMA positive cells, and renal tissue TGF- 1 when compared with the sham groups. The 5/6cit group, when compared with the 5/6tap group, had higher GFR (2.51 + 0.22 vs 1.17 + 0.33 mL/kg/min; p < 0.05), lower fibrosis score (1.83 + 0.88 vs 3.0 + 0.4, p < 0.001), lower -SMA activity (159 + 2.9 vs 187 + 12.3 cells per 1000 interstitial cells, p < 0.05), and lower renal TGF- 1 levels (1771.3 + 239.5 vs 4716.9 + 871.2 pg/mg protein, p < 0.005).
Conclusion: As such, in 5/6 nephrectomized rats, citrate therapy for eight weeks could decrease tubulointerstitial fibrosis mainly by reducing the heightened renal TGF-1 levels and additionally by attenuating the increased myofibroblast activity.

Keywords: Citrate, 5/6 nephrectomy, Tubulointerstitisl fibrosis, TGF-1