Role of renal sympathetic nerve activity in renal failure associated with obstructive jaundice in the rat

Renal Denervation Promotes Atherosclerosis in Hypertensive Apolipoprotein E-Deficient Mice Infused with Angiotensin II

Objective: To determine the effect of renal denervation (RDN) on the severity of atherosclerosis and aortic aneurysm in hypertensive mice. Methods: Hypertension, atherosclerosis and aortic aneurysm were induced by subcutaneous infusion of angiotensin II (1 μg/kg/min) for 28 days in apolipoprotein E-deficient mice. RDN was conducted using combined surgical and local chemical denervation. The norepinephrine concentration in the kidney was measured by high-performance liquid chromatography. Blood pressure was measured by the tail-cuff method. Atherosclerosis was assessed by Sudan IV staining of the aortic arch. The aortic diameter was measured by the morphometric method. The mRNA expression of genes associated with atherosclerosis and aortic aneurysm were analyzed by quantitative PCR. Results: RDN decreased the median norepinephrine content in the kidney by 93.4% (n = 5-7, P = 0.003) 5 days after the procedure, indicating that the RDN procedure was successful. RDN decreased systolic blood pressure in apolipoprotein E-deficient mice. Mice that had RDN had more severe aortic arch atherosclerosis (median percentage of Sudan IV positive area: 13.2% in control mice, n = 12, and 25.4% in mice having RDN, n = 12, P = 0.028). The severity of the atherosclerosis was negatively correlated with the renal norepinephrine content (spearman r = -0.6557, P = 0.005). RDN did not affect the size of aortic aneurysms formed or the incidence of aortic rupture in mice receiving angiotensin II. RDN significantly increased the aortic mRNA expression of matrix metalloproteinase-2 (MMP-2). Conclusion: RDN promoted atherosclerosis in apolipoprotein E-deficient mice infused with angiotensin II associated with upregulation of MMP-2. The higher MMP-2 expression could be the results of the greater amount of atheroma in the RDN mice. The findings suggest further research is needed to assess potentially deleterious effects of RDN in patients.

Protective effects of intravenous anesthetics on kidney tissue in obstructive jaundice

AIM: To evaluate the protective effects on kidney tissue of frequently used intravenous anesthetics (ketamine, propofol, thiopental, and fentanyl) in rats with obstructive jaundice.

METHODS: There is an increased incidence of postoperative acute renal failure in patients with obstructive jaundice. Thirty-two Wistar-albino rats were randomly divided into four equal groups. Laparatomy was performed on each animal in the four groups and common bile ducts were ligated and severed on day 0. After 7 d, laparotomy was again performed using ketamine, propofol, thiopental, or fentanyl anesthesia whose antioxidative properties are well known in oxidative stress in a rat liver model of obstructive jaundice. After 2 h, the rats were sacrificed. Renal tissue specimens were analyzed for catalase, superoxide dismutase and malondialdehyde enzymes activities. All values are expressed as the mean ± SD. P values less than 0.05 were considered statistically significant.

RESULTS: All animals survived without complications until the end of the study. Enlargement in the bile duct and obstructive jaundice were observed in all rats. Catalase was found to be significantly lower in the fentanyl group than in the ketamine (P = 0.039), propofol (P = 0.012), and thiopental (P = 0.001) groups. Superoxide dismutase activities were similar in all groups (P > 0.05). Malondialdehyde was found to be significantly lower in the ketamine group than in the propofol (P = 0.028), thiopental (P = 0.002) and fentanyl (P = 0.005) groups. Malondialdehyde was also lower in the fentanyl group than in the thiopental group (P = 0.001). The results showed that obstructive jaundice sensitizes renal tissue to damage under the different anesthetics.

CONCLUSION: Among the agents tested, ketamine and propofol generated the least amount of oxidative stres on renal tissues in this rat model of obstructive jaundice created by common bile duct ligation. The importance of free radical injury in renal tissue in obstructive jaundice under different intravenous anesthetics during hepatobiliary and liver transplant surgery should be considered for prevention of postoperative acute renal failure.

Renal effects of experimental obstructive jaundice: morphological and functional assessment

BACKGROUND

The pathophysiology of renal impairments occurring in obstructive jaundice has been extensively studied, but the underlying mechanism of these derangements remains unclear. The aim of the present study was to investigate the time-related morphological and functional changes occurring in the kidneys of rats undergoing obstructive jaundice.

METHODS

Histological examination, renal function assessment and determination of (Na + K)-ATPase activity were performed in the kidneys of rats 7, 14, and 21 days following bile duct ligation (BDL) or sham operation (sham).

RESULTS

Glomerular filtration rate was unaffected by BDL throughout the period of the study. Tubular effects occurred at days 7 and 14, being more marked at day 7, and consisted of an increase of about twice in the fractional excretion of sodium and chloride, paralleled by a decreased proximal and distal tubular reabsorption of sodium of about 50 and 40%, respectively. Natriuresis was consistent with augmentation of osmolar clearance but it was not associated with changes in the activity of renal (Na+ + K+)-ATPase. The ability to dilute urine was impaired at days 14 and 21 after BDL. Additionally, these effects were accompanied by decreased tubulointerstitial fibrosis and vasodilation of inner medullary capillaries. At day 21, the parameters of tubular function in BDL and sham groups were not significantly different.

CONCLUSIONS

These data support the view that raised natriuresis taking place in the initial 2 weeks following BDL is due mainly to tubular effects. The contribution of hemodynamic, paracrine and humoral mediators is discussed.

Polyethylene glycol-modified bilirubin oxidase improves hepatic energy charge and urinary prostaglandin levels in rats with obstructive jaundice

BACKGROUNDS/AIMS

No study has so far been conducted to clarify whether the presence of hyperbilirubinemia is detrimental to liver and renal functions. In the present study, the effects of polyethylene glycol-modified bilirubin oxidase (PEG-BOX) therapy on liver and renal function tests, hepatic energy charge and urinary prostaglandin levels were evaluated in a rat model of obstructive jaundice.

METHODS

Sprague-Dawley rats were used in the experimental model of obstructive jaundice. PEG-BOX or an equivalent amount of PEG alone was intravenously injected into the animals and sampling of blood and urine, and liver harvesting were done sequentially after bile duct ligation.

RESULTS

Conventional liver function tests showed no difference between PEG-BOX and control groups. However, bilirubin concentrations in the peripheral blood and liver tissue specimens markedly decreased, and the hepatic energy charge significantly increased in the PEG-BOX group as compared to controls. The blood concentration of bile acid was lower, but its urinary excretion was higher in the PEG-BOX group than in the control group. In vitro incubation of PEG-BOX with serum from rats with obstructive jaundice decreased the concentration of bilirubin but not that of bile acid. The urinary levels of prostaglandin E2 and the thromboxane B2/6-keto-prostaglandin Fla ratio were significantly lower in the PEG-BOX group than in the control group.

CONCLUSIONS

The systemic reduction of bilirubin concentration may contribute to normalization of the urinary levels of prostaglandins and thromboxane B2, to decrease in serum bile acid levels, and to improvement of the hepatic energy charge in obstructive jaundice. These findings suggest that preoperative improvement of jaundice may be beneficial to patients with obstructive jaundice.

The hepato-renal syndrome: renal amino acid transport in bile duct ligated rats (DL)--influence of treatment with triiodothyronine or dexamethasone on renal amino acid handling in amino acid loaded rats

The influence of triiodothyronine or dexamethasone on renal amino acid handling was investigated in anaesthetized, bile duct-ligated (DL) adult female rats. 3 days after DL, glomerular filtration rate (GFR) was unchanged whereas urine flow was decreased. Plasma concentrations of 5 out of 16 amino acids were significantly enhanced after DL. On the other hand, the fractional excretion (FE) of 11 out of 16 amino acids was significantly reduced as a sign of improved reabsorption capacity. Bolus injections of leucine (20 mg/100 g b.wt.), glutamine (45 mg/100 g b.wt.), or taurine (45 mg/100 g b.wt.) were followed by a temporary increase in the FE of the administered amino acids as well of the endogenous amino acids which were not administered. This phenomenon was more pronounced in DL than in control rats. Under load conditions, dexamethasone (60 microg/100 g b.wt.) or triiodothyronine (20 microg/100 g b.wt.) treatment for 3 days, i.p. once daily, was followed by a stimulation of renal amino acid reabsorption in DL rats. The increase in fractional amino acid excretion after amino acid load was significantly lower than in untreated rats. This effect was also more pronounced in DL rats.

Aminoglycoside-associated nephrotoxicity in extrahepatic obstructive jaundice

Experimental data demonstrate that biliary obstruction increases renal sensitivity to gentamicin. In the present study the incidence of and risk factors for aminoglycoside nephrotoxicity were prospectively studied in patients with extrahepatic obstructive jaundice. Two hundred and thirty-seven hospitalized adult patients were classified into three groups. Group I consisted of 84 patients with extrahepatic obstructive jaundice, who received aminoglycoside (gentamicin or tobramycin). Group II consisted of 81 patients with extrahepatic obstructive jaundice, who received either antibiotics other than aminoglycoside or no antimicrobial therapy. Group III consisted of 72 noncholestatic patients receiving aminoglycosides for different disorders. Nephrotoxicity developed in 27 patients (32%) in group I vs 9 patients (11%) in group II and 4 patients (5.6%) in group III (p < 0.00001). In group I, a comparison of patients with and without nephrotoxicity revealed significantly higher values in the former for mean serum bilirubin concentration, initial steady-state trough aminoglycoside concentration and estimated half-life. Stepwise multivariate analysis with nephrotoxicity status as the dependent variable determined that the most significant variable for predicting nephrotoxicity was serum total bilirubin level. In extrahepatic cholestasis a high serum bilirubin level is a distinct factor predisposing to aminoglycoside nephrotoxicity.

Effects of ursodeoxycholic acid on hemodynamic and renal function abnormalities induced by obstructive jaundice in rats

The mechanism of renal function abnormalities in experimental biliary cirrhosis can be partially explained by the absence of gastrointestinal bile flow, which predisposes to translocation of intestinal endotoxin, a potent renal vasoconstrictor. Since bile acids prevent the absorption of intestinal endotoxins, we aimed to evaluate the effects of ursodeoxycholic acid (UDCA) administration on renal function and hemodynamic abnormalities induced by 1 week of obstructive jaundice in rats.

METHODS

Fifty-two rats were used; 30 had ligation of the common bile duct, 22 were sham operated. Bile duct ligated rats were randomly and blindly assigned to receive UDCA (25 mg/kg/day, n = 14) or placebo (n = 16) during 1 week. Sham rats received no treatment. Portal pressure (PP) as well as creatinine clearance (CrCl), urinary sodium (US), and plasma renin activity (PRA) were evaluated. Results are mean +/- SEM, with a significant value of p < 0.05.

RESULTS

Portal pressure (10.4 +/- 1.1 vs. 12.1 +/- 0.8 mm Hg) was significantly lower in UDCA than in placebo-treated rats. ALT serum levels were also significantly lower in bile duct ligated rats receiving UDCA (77.3 +/- 28 IU/L) than in placebo-treated rats (162 +/- 65 IU/L). US (1.1 +/- 0.5 vs. 2.1 +/- 0.3 mEq/24 h) was significantly lower and PRA (6.0 +/- 2.6 vs. 1.9 +/- 1.0 ng Ang 1/mL/h) higher in bile duct ligated than in sham-operated rats. No differences were found between UDCA or placebo-treated bile duct ligated rats. CrCl was similar between sham (0.39 +/- 0.12 mL/min/100 g BW) and UDCA (0.32 +/- 0.16) but significantly lower in placebo-treated (0.28 +/- 0.07) than sham-operated rats (p < 0.05).

CONCLUSION

UDCA administration had very mild effects on renal function abnormalities induced by experimental obstructive jaundice in rats. However, portal hypertension and biochemical abnormalities were partially improved.

Metabolic adaptation of the kidney to hyperammonemia during chronic liver insufficiency in the rat

The aim of this study was to evaluate the role of renal ammonia and glutamine metabolism in the metabolic adaptation to chronic liver insufficiency-induced hyperammonemia in the rat. To this purpose, urinary excretion, renal net exchange and tissue concentrations of ammonia and amino acids were measured in anesthetized, normal control rats that did not undergo surgery, in control rats that underwent sham surgery, in rats that underwent portacaval shunting and in rats that underwent both portacaval shunting and bile duct ligation. Rats that underwent sham surgery and portacaval shunting were pair-fed with rats that underwent portacaval shunting and biliary obstruction, to correct for anorexia in that group, and all rats that were operated on were studied 7 and 14 days after surgery. Arterial ammonia and glutamine levels were elevated in groups that underwent portacaval shunting and portacaval shunting plus biliary obstruction at all time points. At days 7 and 14, total renal ammonia production decreased in rats that underwent portacaval shunting and in rats that underwent portacaval shunting plus biliary obstruction, associated with a 50% decrease in net renal glutamine uptake and strongly diminished net ammonia release into the renal vein, which was most prominent in the group that underwent portacaval shunting plus biliary obstruction. Urinary ammonia excretion was similar in rats that underwent portacaval shunting and in those that underwent sham surgery but was increased more than 200% at days 7 and 14 in rats that underwent portacaval shunting plus biliary obstruction. In this group, in contrast to portacaval-shunted rats, the kidney appeared to be an organ of net ammonia disposal from the body. In separate experiments in unanesthetized, unrestrained rats, similar changes in urinary ammonia excretion were observed without changes in arterial pH, excluding an effect of anesthesia or pH on the obtained results. These results indicate that the kidney plays an important role in the metabolic adaptation to hyperammonemia during chronic liver insufficiency in the rat.

Role of prostacyclin in hemodynamic alterations in conscious rats with extrahepatic or intrahepatic portal hypertension

Although prostaglandins are thought to be involved in the hyperdynamic circulation of portal hypertension, the role of this substance has not been elucidated. Dose-response curves, the hemodynamic effects of prostacyclin (20 micrograms/kg) and its inhibitor indomethacin and measurements of plasma and urinary levels of 6-keto-prostaglandin F1 alpha were compared in three groups of six rats each: normal, with portal vein stenosis and with secondary biliary cirrhosis. Plasma and urinary levels of 6-keto-prostaglandin F1 alpha were higher in rats with portal vein stenosis and cirrhotic rats than in normal rats. Dose-response curves showed similar maximal decreases in arterial pressure in the three groups, whereas the maximal increase in portal pressure was less marked in cirrhotic rats than in normal rats and rats with portal vein stenosis. In normal rats, prostacyclin increased cardiac output by 21% and portal pressure by 41%. Similar increases were observed in rats with portal vein stenosis. In contrast, prostacyclin did not affect cardiac output and portal pressure in cirrhotic rats. Indomethacin induced a more marked vasoconstrictive effect in normal rats than in cirrhotic rats. This study shows that prostacyclin plays a role in the hemodynamic alterations in portal hypertension. Moreover, the hyporeactivity observed in cirrhotic rats suggests that prostacyclin plays a major role in the circulatory changes of portal hypertension due to chronic liver disease.