Preventive Effect Of Tetramethylpyrazine And Ascorbic Acid On Contrast Induced Nephropathy In Rats

Purpose It was hypothesized that rat kidney might be injured by acute administration of gentamicin with iohexol. Tetramethylpyrazine (TMP) of low dose might protect the kidney against contrast induced nephropathy (CIN) in rats. The protective effect of TMP of high dose on CIN in rats was tested.Materials and Methods In part Ⅰ, thirty-two male SD rats were divided into four groups:control (C), gentamicin (G), contrast media (CM), and gentamicin+contrast media (GCM). Following24h urine collection, baseline blood samples were obtained. Gentamicin (80mg/kg, intramuscular) was administered to groups G and GCM respectively. Rats of C and CM groups were given saline. After30min, iohexol (3.5g iodine/kg, intravenous) for groups CM and GCM or saline for groups C and G was injected respectively. After another24h (day2), urine and blood samples were obtained for the assessment of renal function. The left kidneys were excised for morphologic (HE stain), apoptotic (TUNEL stain) and immunohistochemical (Bcl-2and Bax) evaluation. Analysis of variance, followed by Scheffe tests for multiple comparisons was used. In part Ⅱ, twenty-four male SD rats were divided into three groups:saline of low dose (LS), ascorbic acid of low dose (LA) or TMP of low dose (LT). Following24h urine collection, baseline blood samples were obtained. The rats were randomized to inject intramuscularly into the left hindlimb with saline (2mL/kg), ascorbic acid (200mg/kg) or TMP (80mg/kg). After30min, all rats were subjected to the previously detailed CIN protocol in part Ⅰ. In part Ⅲ, twenty-four male SD rats were divided into three groups:saline of high dose (HS), ascorbic acid of high dose (HA) or TMP of high dose (HT). Following24h urine collection, baseline blood samples were obtained. The rats were randomized to inject intramuscularly into the left hindlimb with saline (3mL/kg), ascorbic acid (300mg/kg) or TMP (100mg/kg). After30min, all rats were subjected to the previously detailed CIN protocol in part Ⅰ. The result was also compared with low dose of AA or TMP in part Ⅱ besides analysis of variance in this trial.Results In part Ⅰ, serum creatinine level on day2was higher in group GCM (207 μmol/L±122μmol/L) than that in groups C (47μmol/L±13μmol/L), G (50μmol/L±9μmol/L) and CM (56μmol/L±10μmol/L)(P<0.01, respectively). Creatinine clearance level was lower in group GCM than that in other groups. All rats in group GCM developed larger tubular vacuolization and more evident medullary congestion than those in other groups. The apoptotic cells, the decrease in Bcl-2expression and the increase in Bax expression in group GCM were more than those in other groups. In part Ⅱ, the serum creatinine and urea levels in group LS significantly increased and creatinine clearance level significantly decreased. By contrast, the rise in serum creatinine, urea and creatinine clearance levels were no statistical difference in rats pretreated with LA or LT. Tubular vacuolization and medullary congestion in group LT were significantly improved compared with those in group LS. In group LA, only tubular vacuolization was decreased. The apoptosis in renal tubular cells in groups LT and LA was less than that in group LS. LA or LT similarly reversed the enhancement in bax expression and the reduction in bcl-2expression. In part Ⅲ, the changes of serum creatinine, urea and creatinine clearance levels in all groups were no statistical difference except that CIN occurred in1rat in group HS. Tubular vacuolization in group HA were significantly improved compared with that in group HS. But in group HT, tubular vacuolization and medullary congestion were all significantly less compared with those in group HS. HA and HT similarly reversed the enhancement in bax expression, the reduction in bcl-2expression and apoptosis in renal tubular cells. There was no difference between LA and HA groups in biochemical, morphologic, apoptotic and immunohistochemical findings. The comparison of LT and HT groups in all findings was no difference, either.Conclusion The trial demonstrated that the acute combination of gentamicin with iohexol could induce acute renal injury in rats. TMP of threshold dose could confer protection against CIN in rats. There was no difference between high and threshold dose of TMP in CIN prevention.