Background. Surgery on patients with obstructive jaundice is associated with a significant risk of postoperative renal failure. Bile acids are implicated as nephrotoxins because they accumulate in ...the plasma and the kidney becomes their only excretory route in cholestasis. The experimental evidence favoring this proposal is inadequate and unconvincing. Therefore, we designed an animal experiment involving bile duct ligated (BDL) rats in which we could correlate variations in serum and urine bile acids with indices of nephrotoxicity and renal function. Hypothesis. Bile acids are putative nephrotoxins. Materials and Methods. Total serum and urine bile acid concentrations and profiles were determined using liquid chromatography gas chromatography mass spectrometry selected ion monitoring. Nephrotoxicity was assessed by renal histopathology and by determination of the urinary activities of the following enzymes: muramidase, glutamate dehydrogenase, alkaline phosphatase, N-acetyl-β-D-glucosaminidase, and lactate dehydrogenase. Renal function was assessed by measuring urine osmolality, daily osmolar excretion, sodium excretion (UNaV), potassium excretion (UKV), and total protein and albumin excretion. Results. Maximum plasma concentrations and renal clearance of bile acids occurred between the third or fourth postoperative day following BDL. This peak coincided with maximal disruption of proximal convoluted tubule architecture and postoperative changes in renal function-increased urine flow rate and decreases in urine osmolality and sodium excretion. Thereafter, 1) plasma levels of bile acids returned toward normal levels, 2) urinary bile acid clearance declined, 3) normal renal histology was restored, and 4) normal renal function was reestablished. Throughout this period, fluctuations in enzymuria were evident. However, these shifts did not coincide with plasma and urine bile acid concentrations and histological and functional changes. Discussion and Conclusions. Transient functional impairment of renal cation and water transport and nonspecific morphological changes in the proximal convoluted tubule occur 3 to 4 days following bile duct ligation in rats. These functional and morphological changes occurred when plasma total and urinary bile acids were at their peaks. Although it is tempting to equate association with causality, we cannot implicate bile acids as being responsible for the aberrations in renal function and structure following BDL. Accordingly, we have concluded that elevated plasma concentrations of bile acids are renal exacerbates acting in concert with other factors, be they prerenal or renal in origin to precipitate a cascade of events leading to postoperative renal failure in cholestasis.
Bile acids have been proposed as a causative factor for the cardiomyopathy of cholestatic liver disease, since they cause negative inotropism and chronotropism and attenuate cardiac responsiveness to ...sympathetic stimulation. Bile acids can also modify membrane fluidity and generate reactive oxygen species (ROS). The effects of 10
−6–10
−3 M deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA) and their taurine conjugates, TDCA and TCDCA, on (1) the binding characteristics of β-adrenoceptors, (2) membrane fluidity, and (3) the extent of lipid peroxidation in rat cardiac membranes were assessed. The results were compared to the effects of the oxidant, 10
−4–10
−3 M hydrogen peroxide (H
2O
2), and the membrane-fluidizing compound, 5 × 10
−5 M 2-(2-methoxyethoxy)ethyl 8-(cis-2-
n-octylcyclopropyl)octanoate (A
2C). Cardiac β-adrenoceptor density alone was reduced at 10
−4 M bile acid concentration while, at 10
−3 M bile acids, reductions in both receptor density and affinity were seen. At 10
−4 M H
2O
2, receptor number and affinity were reduced, whereas A
2C increased receptor affinity without affecting receptor density. Bile acids (10
−3 M) and 10
−4 M H
2O
2 reduced membrane fluidity. H
2O
2 caused a concentration-dependent increase in the extent of lipid peroxidation, whereas the bile acids and A
2C had no effect. Bile acids (10
−4 M) reduced β-adrenoceptor density in the absence of variations in membrane fluidity and in the extent of membrane lipid peroxidation. This result suggests that bile acids, at concentrations equivalent to the plasma/serum total or estimated free bile acid concentration, may have a possible role in the etiology of cardiomyopathy of cholestatic liver disease. At 10
−3 M bile acid concentration, β-adrenoceptor number and affinity were adversely affected, accompanied by a decrease in membrane fluidity but without any significant increase in the extent of membrane lipid peroxidation. Although cardiac β-adrenoceptor density and affinity and membrane fluidity were adversely affected by bile acids, the relevance of these findings to our understanding of the etiological basis of hepatic cardiomyopathy is questionable, since such concentrations exceeded the highest concentrations seen in the plasma and/or tissues of patients with cholestatic liver disease.
We have examined the effects of bile duct ligation on vascular and extravascular smooth muscle responsiveness to noradrenaline and tyramine using isolated rat hindlimb perfusion, and portal vein and ...vas deferens preparations. Bile duct ligation reduced the contractile responses to noradrenaline of vascular and extravascular smooth muscle. Exposure of smooth muscle to some bile salts caused a reduction in contractility. This effect was dependent upon bile salt type and concentration. These studies in vitro suggest that the reduced total peripheral resistance and hypotension seen in obstructive jaundice cannot be explained by a spasmolytic effect of some of the bile salts on smooth muscle.
Cholestasis depresses cardiovascular function and responsiveness. In a previous study, the 3-day bile duct manipulated (BDM) rat was validated as the appropriate control for studying in vitro ...vascular neuroeffector mechanisms in cholestasis. The present study reports the findings on the effect of BDM on cardiovascular function and responsiveness in conscious rats. Cardiovascular responsiveness was assessed by measuring the in vivo pressor responses to a 90° head-up vertical tilt, a controlled hemorrhage, and to intravenously infused norepinephrine, tyramine, the indirectly acting sympathomimetic drug, isoproterenol, the nonselective β-adrenoceptor agonist, angiotensin I, and angiotensin II. The concentrations of catecholamines and plasma renin activity measured in plasma samples obtained from conscious chronically arterial catheterized BDM rats were compared to identical data obtained from rats in which the bile duct was not manipulated. There were no differences in cardiovascular responsiveness to any of these procedures or drug infusions between the two groups of rats. Plasma catecholamine concentrations and renin activities in the BDM rats were not significantly different from control rats. Although no differences in cardiovascular responsiveness between BDM and control rats were observed, these data confirm the choice of the BDM as the control group for experiments assessing the effects of cholestasis on cardiovascular responsiveness.
The sources of calcium for cholecystokinin octapeptide (CCK-OP)-induced gallbladder smooth muscle contraction are considered both extracellular and intracellular, but the relative need for ...intracellular calcium especially at low, physiological concentrations is not clear. To better define the calcium sources responsible for guinea-pig gallbladder contractions in vitro, we inhibited calcium influx using the calcium channel blocker, methoxyverapamil, and a calcium-free Krebs' solution. Availability and release of intracellular calcium stores were depleted by strontium substitution and ryanodine. CCK-OP was compared to bethanechol and potassium chloride (KCl). Preventing calcium influx with 10(-5) M methoxyverapamil depressed the responses to CCK-OP, bethanechol and KCl. Methoxyverapamil, however, had little effect on the time-dependent generation of tension to CCK-OP, but significantly reduced the response to bethanechol and KCl, each at ED50. The duration of the contractile response in the calcium-free Krebs' solution to CCK-OP was longer than that for bethanechol. Strontium (2.5 mM) significantly attenuated the response to CCK-OP and bethanechol, but not to KCl. Ryanodine significantly reduced contractions induced by CCK-OP but not for bethanechol, both at low dose ED25. These results indicate that contraction of the guinea-pig gallbladder induced by CCK-OP, bethanechol and KCl requires extracellular calcium influx. Further, the initiation and maintenance of contraction by CCK-OP and bethanechol necessitates calcium mobilisation from intracellular stores. CCK-OP may have a greater penchant for these calcium stores, particularly at physiological doses.
Lipophilic bile acids, such as deoxycholic acid (DCA), are nonspecific endothelium-independent vasorelaxants whose underlying basis is complex, involving membrane calcium channels blockade and ...receptor antagonism. The vasorelaxant action of these acids has also been linked to the generation of reactive oxygen species and an increased extent of lipid peroxidation. Ursodeoxycholic acid (UDCA) is a naturally occurring tertiary dihydroxy hydrophilic acid whose mechanism of action has been attributed to minimizing the effects of lipophilic bile acids. Hence, we considered UDCA might be a useful pharmacological tool to delineate the role of enhanced lipid peroxidation in lipophilic bile acid-induced vasorelaxation. UDCA abrogates in vitro DCA-induced vasorelaxation in rat aortic rings and can suppress DCA-initiated lipid peroxidation in vascular smooth muscle microsomal membrane fractions prepared from the rat aortae. Three different studies were performed. In study 1, the ability of UDCA to restore the DCA-blunted contractile response to the alpha1-adrenoceptor, phenylephrine in rat aortic rings, was evaluated. In study 2, the ability of UDCA to restore DCA-induced vasorelaxation in precontracted rat aortic rings was assessed. In study 3, the ability of UDCA to suppress the increased extent of lipid peroxidation effected by DCA in vascular smooth muscle microsomal membrane fractions prepared from rat aortae was measured using the thiobarbituric acid reactive substance (TBARS) assay. UDCA, at a concentration equivalent to that seen in the plasma of patients with cholestatic liver disease treated with the bile acid, partially restored DCA-induced impaired contractility, prevented DCA-induced vasorelaxation, and abolished DCA-induced increases in the extent of lipid peroxidation. In conclusion, these data suggest that DCA-induced vasorelaxation is mediated by increasing the extent of lipid peroxidation in vascular tissue.
1. Systemic hypotension, blunted cardiovascular responsiveness to noradrenaline and an abnormal hypertensive pressor response to a postural change have been described in cirrhotic patients. 2. We ...have examined the role of blunted responsiveness in these abnormalities by studying basal arterial blood pressure and its response to a postural change (vertical head-up 90 degrees tilting) in conscious and pithed CCl4-treated (cirrhotic) rats, as well as assessing the pressor response to noradrenaline in vivo and the vascular contractile response to noradrenaline in vitro. 3. A diminished hypotensive response to a change in posture was found in pre-cirrhotic portal hypertensive rats, whereas an inverted hypertensive pressor response in the face of systemic hypotension occurred in the cirrhotic rats with portal hypertension. 4. The inverted pressor response was abolished in the pithed portal hypertensive cirrhotic rats. 5. The pressor response to noradrenaline in vivo in conscious cirrhotic rats and the vascular contractile responsiveness to noradrenaline in vitro were intact. 6. We conclude that blunted responsiveness to noradrenaline is not a contributory factor to the development of systemic hypotension or the inverted pressor response to a change in posture in cirrhosis.
Combination therapy of interferon-alpha (IFNalpha) and the oral nucleoside analog, ribavirin is the standard treatment for individuals suffering from hepatitis C virus (HCV) infection. Several ...studies have shown combination therapy of IFN and antioxidants is therapeutically beneficial in these patients. Ursodeoxycholic acid (UDCA) is a hydrophilic bile acid possessing antioxidant properties. This study evaluated the clinical outcome and extent of oxidative stress in a group of non-responding and disease-relapsed HCV patients treated with IFNalpha, ribavirin and UDCA (triple therapy) for 6 months.
Twenty patients with chronic HCV disease were treated with triple therapy for six months. During this period, they were monitored for the presence of HCV RNA, standard serum parameters of liver function and the plasma levels of lipid peroxides (LP) and glutathione (GSH) as indices of oxidative stress. The patients were reassessed six months after completion of treatment.
During the 6-month treatment period, the health status of the patients improved reflected by falls in the serum activities of alanine and aspartate aminotransferases and gamma-glutamyl transpeptidase and an initial lowering of viral (HCV RNA) load. Six months after cessation of treatment, the patients showed biochemical and virological evidence of disease relapse. The elevated plasma LP levels normalized during the treatment period and remained within normal levels 6 months after completion of treatment. Plasma GSH levels fluctuated within the normal range over the 12-month observation period.
Treatment of individuals with chronic HCV hepatitis with triple therapy comprising IFNalpha, ribavirin and UDCA improves the health status, as well as lowering the extent of oxidative stress in these individuals. This treatment regimen also resulted in a sustained lowering of plasma lipid peroxide levels in the face of laboratory evidence of disease relapse. This preliminary study is unable to provide an apt explanation for the persistence of normal plasma LP levels in the face of evidence of disease relapse 6 months after completion of treatment. However, we believe these preliminary findings are sufficiently intriguing to warrant further study. Such investigations should include more patients with assessment of the extent of hepatic fibrosis during and after completion of treatment to determine whether this treatment can modify the natural progress of the disease.
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