| Objective: The patients with acute renal failure (ARF) remain high mortality. It has long been recongnized that renal tubular cell injury or death is the main histopathological change in ARF. ARF is usually reversible, and the recovery depends on inhibiting the early apoptosis and accelerating the regeneration of renal tubular cells, however, the mechanism of the molecular regulation of injury and regeneration in renal tubular cells has not yet been fully clarified. Augmenter of liver regeneration (ALR) is a newly recongnized growth factor that can promote hepatocyte proliferation and prevent liver fibrosis. We have known that the expression of ALR in renal tissue is high, but we haven't known its biological activity in the kidney. Our study found that the protein of ALRexpressed in the renal epithelial cells in medulla of healthy rat kiney, however, in anti-Thy1.1 nephritis it expressed not only in renal medulla but also in some tubular epithelia near the glomeruli in renal cortex. The expression of ALR in the renal tubular epithelia suggested that ALR directly or indirectly participate in maintenance the normal structure and function of renal tubular epithelia.In order to investigate the role of ALR in ARF, we studied the expression of ALR in renal tissue of rats with gentamicin induced ARF and its relationship with the proliferation of renal tubular cells. At the same time we investigated the effect of rrALR on proliferation and apoptosis of renal tubular cell (HK2) in vitro. Method:(1) The rat model of ARF was established by intraperitoneal injection of gentamincin sulfate for consecutive 7 days. Serum BUN, Scr and urinary NAG were measured by routine method. The morphological changes were studied by HE and PAS staining.(2) The expression of ALR and PCNA in renal tissue was detected by immunohistochemistry and western blot.(3) The HK2 cells were divided into normal group, rrALR treated group, gentamicin injured group, gentamincin and rrALR cocultured group. The effects of rrALR on HK2 proliferation were evaluated by 3H-TdRincorporation.(4) The apoptosis of HK2 cultured with gentamicin or gentamicin and rrALR assessed by AO/EB staining and flow cytometer using Annexin V-FITC and propidium iodide (PI) staining. Results: 1. Results in vivo(1) UNAG levels in gentamicin treated rats significantly increased on day 4 after toxic injury compared with control rats, while BUN and Scr levels significantly increased on day 6. The peak levels occurred on day 8 and decreased gradually to almost normal level from day 12 to day 21.(2) Morphological changes: The renal tissue of treated rats was examined by light microscopy. Proximal tubular cells displayed mild alterations after four days of gentamincin injection. Morphological abnormality of the proximal tubules, such as focal cell necrosis and cell turnover was observed on day 6. The typical gentamincin induced frank proximal tubules necrosis was observed after eight-day treatment. From day 12, the structure of the tubules began to recover. They almost exhibited the morphological normality after twenty-one-day treatment.(3) Immunohistochemistry and Western Blot(1) In normal rats, ALR were mainly expressed in Henle's loop, distal tubules and collecting ducts located in renal medulla. However, ALRexpressed not only in above region but also in injured and regenerating tubular cells in treated rats with gentamicin. The protein level of ALR significantly increased on day 4 after toxic injury compared with control rats. It reached the highest level on day 8, went down on day 12 and returned to almost normal level on day 21. ALR didn't express in glomeruli in all rats.(2) The number of PCNA positive tubular cells was low in control rats, however, in gentamicin treated rats, the positive number increased on day 4 and reached its peak on day 8, went down on day 12 and back gradually to almost normal level on day 21. The proliferating index (PI, positive tubular cells/all tubular cells) reflecting the degree of tubular cell proliferation wer...
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