engleski

The effect of unilateral obstruction and anti-angiotensin II treatment on renal tubule and interstitial cell apoptosis and fibrosis in rats

Apoptosis in general is known to proceed initially along distinct pathways, which later converge into a common arm characterised by orderly activation of caspases. In this study, we examined the apoptosis and fibrosis of tubular and interstitial cells of the kidney in rats with unilateral ureteral obstruction (UUO). We explored the effect of the administration of an angiotensin converting enzyme (ACE) inhibitor- cilazapril and an angiotensin II (Ang II) type I receptor antagonist- losartan on these histological changes. Sixty-four Wistar male rats, two months old, were used in these experiments. Sham-operated and UUO-rats were subject to no treatment (control, N=20), or to the treatment with either losartan (30mg/kg, orally, N=22), or cilazapril (10mg/kg, orally, N=22). The kidneys were removed at 10th postoperative day. One sagital half was frozen at -70 C degrees and the other half of the kidney was processed for histology. Apoptosis was asssessed in hematoxilin-eosin (HE)- and TUNEL (terminal deoxynucleotidyl transferase nick-end labelling)- stained slides. The number of apoptotic cells in tubular segments as well as in the interstitium is expressed as a mean from 10 consecutive non overlapping high-power (400x) fields (hpf). The corellation between the two methods was determined. For analyzing the fibrotic changes of tubular and interstitial cells, Gomori staining and morphometric measuring was done. A frozen sagital half of the kidney was used for the determination of caspase-3 activity. The caspase-3 activity measurement was performed by the colorimetric method according to the manufacturer's instructions (Biomol QuantiZyme TM Assay System). Tubular cells apoptosis peaked ten days after ureter ligation UUO vs. sham UUO, p<0.05), remained high between days 10 and 14, and decreased thereafter. In a group treated with cilazapril there was a significant change of apoptotic interstitial cells compared with control group(p<0.05). Colorimetric measurement of caspase-3 activity has shown low levels in control kidneys and in contralateral kidneys. The obstructed kidneys displayed an increased caspase-3 activity in all three experimental groups. Significant increase of interstitial fibrosis in cortex and medula of rat kidneys with UUO was observed. The current study documents an increase in tubule as well as interstitial cell apoptosis following UUO in rats. Treatment with cilazapril significantly increases the number of interstitial apoptotic cells in obstructed kidneys. An increased caspase-3 activity in kidneys with ureteral obstruction correlates with renal cell apoptosis. This finding suggests that caspase-3 may serve as a mediator of renal cell apoptosis induced by urinary obstruction, and may be relevant to renal cell apoptosis as a common feature of chronic tubulointerstitial injury in general. Interstitial fibrosis is increased in kidneys of rats with UUO.

renal obstruction; apoptosis

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