Arieh Bomzon

Role of cardiac structural and functional abnormalities in the pathogenesis of hyperdynamic circulation and renal sodium retention in cirrhosis.

The aim of this study was to assess the relationship between subtle cardiovascular abnormalities and abnormal sodium handling in cirrhosis. A total of 35 biopsy-proven patients with cirrhosis with or without ascites and 14 age-matched controls underwent two-dimensional echocardiography and radionuclide angiography for assessment of cardiac volumes, structural changes and systolic and diastolic functions under strict metabolic conditions of a sodium intake of 22 mmol/day. Cardiac output, systemic vascular resistance and pressure/volume relationship (an index of cardiac contractility) were calculated. Eight controls and 14 patients with non-ascitic cirrhosis underwent repeat volume measurements and the pressure/volume relationship was re-evaluated after consuming a diet containing 200 mmol of sodium/day for 7 days. Ascitic cirrhotic patients had significant reductions in (i) cardiac pre-load (end diastolic volume 106+/-9 ml; P<0.05 compared with controls), due to relatively thicker left ventricular wall and septum (P<0.05); (ii) afterload (systemic vascular resistance 992+/-84 dyn.s.cm(-5); P<0. 05 compared with controls) due to systemic arterial vasodilatation; and (iii) reversal of the pressure/volume relationship, indicating contractility dysfunction. Increased cardiac output (6.12+/-0.45 litres/min; P<0.05 compared with controls) was due to a significantly increased heart rate. Pre-ascitic cirrhotic patients had contractile dysfunction, which was accentuated when challenged with a dietary sodium load, associated with renal sodium retention (urinary sodium excretion 162+/-12 mmol/day, compared with 197+/-12 mmol/day in controls; P<0.05). Cardiac output was maintained, since the pre-load was normal or increased, despite a mild degree of ventricular thickening, indicating some diastolic dysfunction. We conclude that: (i) contractile dysfunction is present in cirrhosis and is aggravated by a sodium load; (ii) an increased pre-load in the pre-ascitic patients compensates for the cardiac dysfunction; and (iii) in ascitic patients, a reduced afterload, manifested as systemic arterial vasodilatation, compensates for a reduced pre-load and contractile dysfunction. Cirrhotic cardiomyopathy may well play a pathogenic role in the complications of cirrhosis.

Aqueous Extracts of Teucrium polium Possess Remarkable Antioxidant Activity In Vitro

Teucrium polium L. (Lamiaceae) (RDC 1117) is a medicinal plant whose species have been used for over 2000 years in traditional medicine due to its diuretic, diaphoretic, tonic, antipyretic, antispasmodic and cholagogic properties. The therapeutic benefit of medicinal plants is often attributed to their antioxidant properties. We previously reported that an aqueous extract of the leaves and stems of this plant could inhibit iron-induced lipid peroxidation in rat liver homogenate at concentrations that were not toxic to cultured hepatic cells. Others have reported that organic extracts of the aerial components of this plant could inhibit oxidative processes. Against this background, we felt further investigation on the antioxidant action of the extract of T. polium prepared according to traditional Arab medicine was warranted. Accordingly, we assessed (i) its ability to inhibit (a) oxidation of β-carotene, (b) 2,2′-azobis(2-amidinopropan) dihydrochloride (AAPH)-induced plasma oxidation and (c) iron-induced lipid peroxidation in rat liver homogenates; (ii) to scavenge the superoxide (O2•−) radical and the hydroxyl radical (OH•); (iii) its effects on the enzyme xanthine oxidase activity; (iv) its capacity to bind iron; and (v) its effect on cell glutathione (GSH) homeostasis in cultured Hep G2 cells. We found that the extract (i) inhibited (a) oxidation of β-carotene, (b) AAPH-induced plasma oxidation (c) Fe2+-induced lipid peroxidation in rat liver homogenates (IC50 = 7 ± 2 μg ml−1); (ii) scavenged O2•−(IC50 = 12 ± 3 μg ml−1) and OH• (IC50 = 66 ± 20 μg ml−1); (iii) binds iron (IC50 = 79 ± 17 μg ml−1); and (iv) tended to increase intracellular GSH levels resulting in a decrease in the GSSG/GSH ratio. These results demonstrate that the extract prepared from the T. polium possesses antioxidant activity in vitro. Further investigations are needed to verify whether this antioxidant effect occurs in vivo.

Oxidative stress and vascular smooth muscle cell function in liver disease.

Reactive oxygen species and reactive nitroxy species are now being recognized as regulatory molecules in signaling pathways influencing contractile and noncontractile functions of healthy vascular smooth muscle cells. In liver disease, oxidative stress is a systemic phenomenon, whose extent correlates with the severity of disease. A role for oxidative stress in the development of the hyperdynamic circulation in portal hypertension has been proposed. Evaluation of the limited available data indicates that it is premature to conclude that oxidative stress per se impacts on vascular smooth muscle cell function in liver disease.

Ursodeoxycholic Acid Suppresses Extent of Lipid Peroxidation in Diseased Liver in Experimental Cholestatic Liver Disease

The therapeutic benefit of ursodeoxycholic acid (UDCA) in treating cholestatic liver disease is globally recognized. It is generally accepted that the mechanism of action of UDCA can be attributed to several diverse processes that appear to be uniformly targeted towards minimizing the deleterious actions of accumulated hydrophobic bile acids in the cholestatic liver. Since hydrophobic bile acids are prooxidants, emerging in vitro evidence suggests that UDCA may have an antioxidant mechanism of action. We hypothesize that UDCA suppresses the extent of lipid peroxidation in the cholestatic liver. This hypothesis was tested by assessing the extent of lipid peroxidation in livers harvested from chronic bile duct ligated (CBDL) rats dosed daily for 24 days with 5, 10, or 15 mg/kg UDCA. The extent of lipid peroxidation was evaluated by determining the hepatic content of conjugated dienes, lipid peroxides, and malondialdehyde. The data were compared with identical data collected from unoperated control and 24-day bile duct manipulated (SO) rats. In the two groups of control rats, UDCA has no effect on the serum indices of liver function. In CBDL rats, UDCA suppressed the increased extent of lipid peroxidation in the liver in a dose-dependent manner in the absence of improvement of laboratory parameters of liver function and hepatic architecture. In conclusion, UDCA suppresses the augmented extent of lipid peroxidation in the diseased liver of CBDL rats.

Effects of bile acids on ventricular muscle contraction and electrophysiological properties: studies in rat papillary muscle and isolated ventricular myocytes

SummaryThe effects of sodium salts of various bile acids on the contractile force and the electrophysiological properties of rat ventricular muscle were studied in vitro. Primary, conjugated, and secondary bile acids were studied in a concentration range of 10−9−10−6 mol/l, which corresponds to concentrations found in the plasm of patients with cholestatic jaundice. In general, the bile acid induced a negative inotropic effect which was manifested as a reduction in active tension, maximum rate of tension activation, and maximum rate of tension relaxation. Twitch duration and time to peak tension were unaffected by the bile acids. The negative inotropism was associated with a reduction in ventricular action potential duration. Resting potential, action potential amplitude, and maximum upstroke velocity of phase 0 depolarization were unaffected. Voltage clamp experiments in rat ventricular myocytes demonstrated that sodium taurocholate decreased the slow inward current and slightly increased the outward potassium current. Hence, these effects on the membrane currents are probably responsible for the negative inotropic effect.

Increase in central and peripheral benzodiazepine receptors following surgery

[3H]Flunitrazepam, [3H]PK 11195, [3H]quinuclidinyl benzilate (QNB) and monoamine oxidase (MAO) A and B activity were measured in male rats 1, 3 and 7 days following laparotomy. The surgery resulted in the up-regulation of central benzodiazepine (BZ) receptors in cerebral cortex and of peripheral BZ binding sites in brain and kidney on the first and third days after operation. This increase was followed by a decrease to normal range 7 days after the surgical procedure. [3H]QNB binding to muscarinic receptors in the cerebral cortex as well as MAO A and B activity in rat cerebral cortex and kidney were not affected by the surgical manipulation. The modulatory effect of surgery on BZ receptors corresponds to stages of the healing process in surgical wounds.

Are Bile Acids Involved in the Renal Dysfunction of Obstructive Jaundice? An Experimental Study in Bile Duct Ligated Rats

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.

Fertilization-Induced Changes in Growth Parameters and Antioxidant Activity of Medicinal Plants Used in Traditional Arab Medicine

In response to increased popularity and greater demand for medicinal plants, a number of conservation groups are recommending that wild medicinal plants be brought into cultivation systems. We collected four medicinal herbs Cichorium pumilum, Eryngium creticum, Pistacia palaestina and Teucrium polium used in traditional Arab medicine for greenhouse cultivation to assess the effects of different fertilization regimes on their growth and antioxidant activity. Wild seedlings were collected and fertilized with either 100% Hoagland solution, 50% Hoagland solution, 20% Hoagland solution or irrigated with tap water. Plant height was measured and the number of green leaves and branches counted weekly. Thereafter, the aboveground parts of plants were harvested for preparing a water-soluble powder extracts of which antioxidant activity was measured by their ability to suppress the oxidation of β-carotene. Of the fertilization regimes, we found either 20 or 50% Hoagland solution produced the most consistent response of the plant growth parameters. All powders prepared from the four wild growing plants inhibited oxidation of β-carotene. Increasing the amount of fertilizer caused a significant concentration-dependent increase in antioxidant activity of the cultivated T. polium compared with the wild type. In contrast, increasing the amount of fertilizer caused a significant concentration-dependent reduction in the antioxidant activity of powders prepared from the cultivated E. creticum when compared with wild plants. Our results showed that cultivation success should not rely solely on parameters of growth but should incorporate assessment related to indices of therapeutic potential.

Systemic hypotension and presser responsiveness in cholestasis: A study in conscious 3-day bile duct ligated rats

It has been postulated that the physiological basis for systemic hypotension in cholestatic liver disease is the attenuated responsiveness of the cardiovascular system to sympathetic stimulation. Using conscious 3-day bile duct ligated rats, we tested this hypothesis by measuring the vasopressor and vasodilator responses following intravenous infusions of norepinephrine, tyramine, angiotensin II, angiotensin I and isoproterenol, in conjunction with the pressor responses to a head-up vertical tilt and a controlled hemorrhage. The results were compared to those obtained in conscious sham-operated rats. Bile duct ligation reduced the mean arterial blood pressure without a significant increase in heart rate. The pressor responses to the aforementioned drugs obtained in the bile-duct ligated rats were significantly attenuated from those the sham-operated rats. In contrast, bile duct ligation had no effect on the pressor responses to tilting and hemorrhage when compared to the responses obtained in the sham-operated rats. Despite the presence of systemic hypotension and attenuation of pressor response to vasoactive drugs, the ability of the cardiovascular system to respond to physiological stimuli appears to be intact in this model. Therefore, we conclude that blunted pressor responsiveness of the cardiovascular system is probably not an important physiological determinant of systemic hypotension in cholestatic liver disease.

On the in vitro vasoactivity of bile acids.

We compared the vasorelaxant action of nine different bile acids and correlated their vasorelaxant activity with their individual indices for hydrophobicity or lipophilicity. Vasorelaxant activity correlated with the relative lipid solubility of bile acids with lipophilic bile acids exhibiting the greatest vasorelaxant activity with modest to no vasorelaxant activity exhibited by hydrophilic bile acids. We also investigated whether bile acid‐induced vasorelaxation is mediated by antagonism of a prototypal contractile receptor, the α1‐adrenoceptor, by stimulation of a bile acid surface membrane receptor, by the release of endothelium‐derived relaxant factors, by promoting the generation of reactive oxygen species and increasing the extent of lipid peroxidation, or by modifying membrane fluidity. Lipophilic bile acids induce vasorelaxation possibly by antagonizing α1‐adrenoceptors, a phenomenon that manifests itself as a lowering of the affinity of vascular α1‐adrenoceptors. Bile acid‐induced vasorelaxation was not dependent upon stimulation of a bile acid surface membrane receptor or the release of endothelium‐derived relaxant factors. Lipophilic bile acids can also increase the extent of lipid peroxidation with a subtle reduction in the fluidity of rat vascular smooth muscle membranes not associated with loss of membrane cholesterol or phospholipid. We have concluded that lipophilic bile acids are non‐selective vasorelaxants whose mechanism of action is a multifaceted process involving antagonism of contractile surface membrane receptors possibly effected by an increased extent of lipid peroxidation and/or membrane fluidity but occurs independent of the release of endothelial‐derived relaxant factors or stimulation of a surface membrane bile acid binding site.