[The expression of connective tissue growth factor in renal cortex of 5/6 nephrectomized rats and its modulation by fluvastatin].

ABSTRACT

OBJECTIVE: To investigate the connective tissue growth factor (CTGF) mRNA expression in the renal cortex of 5/6 nephrectomized rats and its modulation by fluvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor. METHODS: Twenty-four rats underwent operation 2 times during the first operation 2/3 of the left kidney was resected, and the right kidney was resected completely one week after. The 24 5/6 nephrectomized rats were randomly divided into 2 groups untreated 5/6 nephrectomized group (model group, n=12) and fluvastatin-treated 5/6 nephrectomized group (treatment group, fluvastatin was orally administered 7 mg.kg(-1).d(-1) for 13 weeks, n=12), and 6 sham-operated rats served as control (sham operation group). In the weeks 2, 4, 8, and 13 after the second operation metabolic cage was used to collect the 24-hour urine 2 times. Urine protein was examined by biuret reaction so as to calculate urinary protein excretion. By the end of experiment blood was collected to examine the serum cholesterol, triglyceride, urea nitrogen, and creatinine contents. The rats were killed and their kidneys taken out. The CTGF mRNA expression in the renal cortex was detected by RT-PCR. Immunohistochemistry was used to examine the expression of transforming growth factor-beta1 (TGF-beta1), type IV collagen and fibronectin in the glomeruli. Renal pathological changes and glomerular sclerosis index (GSI) were evaluated as well. RESULTS: At the end of the experiment, the mean urinary protein excretion in the model group was 305.4 mg/24 h, significantly higher than that in the treatment group (230.9 mg/24 h, P<0.01) and the sham operation group (5.6 mg/24 h, P<0.01) The serum urea nitrogen of the model group was (24.5 +/- 4.9) mmol/L, significantly higher than that of the treatment group [(15.8 +/- 3.9) mmol/L, P<0.05] and that of the sham-operated group (7.4 +/- 0.3 mmol/L, P<0.01). The serum creatinine (P<0.05) of the model group was 88 micromol/L +/- 14 micromol/L, significantly higher than that of the treatment group [(58 +/- 5) micromol/L, P<0.05)] and that of the sham-operated group [(54 +/- 5) micromol/L, P<0.05]. The creatinine clearance rate of the model group was (1.7 +/- 0.7) ml.min(-1).kg(-1), significantly lower than that of the treated group [(3.2 +/- 1.1) ml.min(-1).kg(-1), P<0.05] and that of the sham-operated group [(3.9 +/- 1.5) ml.min(-1).kg(-1), P<0.05]. The glomerular sclerosis index (GSI) in the model group was 41.8 +/- 11.5, significantly higher than that in the sham operation group (2.2 +/- 1.3, P<0.01) and the treatment group (23.4 +/- 6.1, P<0.05). The mean optical density of CTGF mRNA expression in the renal cortex of the model group was a 3 times that of the sham operation group, and the mean optical density of CTGF mRNA expression in the renal cortex of the treatment group was lower by 55.4% compared with that of the model group (P<0.01). The glomerular expressions of TGF-beta1, type IV collagen and fibronectin were significantly up-regulated in the model group in comparison with those in the sham operation group (all P<0.01). The glomerular protein expressions of TGF-beta1, type IV collagen and fibronectin were significantly weaker in the fluvastatin treatment group as compared with the model group (all P<0.01). CONCLUSION: CTGF mRNA expression is markedly upregulated in the renal cortex of 5/6 nephrectomized rats. Fluvastatin suppresses the increased CTGF mRNA expression in renal cortex and ameliorates the glomerular extracellular matrix accumulation.