Chronic verapamil administration lowers portal pressure and improves hepatic function in rats with liver cirrhosis

Effect of early bosentan administration on the development of esophageal varices in cirrhotic rats: experimental study in Wistar rats

BACKGROUND

This study was conducted to investigate the effect of chronic bosentan administration on the development of esophageal varices in carbon tetrachloride-induced cirrhosis in rats.

METHODS

For the development of liver cirrhosis and esophageal varices, 60 rats underwent ligation of the left adrenal vein, followed by phenobarbital and carbon tetrachloride administration. Two weeks after the beginning of carbon tetrachloride administration, rats were separated into two groups. In group I, comprising 30 rats, bosentan was continuously administered throughout the study, whereas in group II, also 30 rats, placebo instead of bosentan was continuously administered. Hemodynamic studies and morphometric analysis of the lower esophagus were performed after complete induction of cirrhosis. The total number of veins counted in the submucosa, the number of submucosal veins/mm(2) of submucosa, the total submucosal area occupied by vessels, the mean cross-sectional vessel area, the relative submucosal area (percentage) occupied by vessels, and the area of the single most-dilated submucosal vein were studied.

RESULTS

Bosentan induced a significant (P < 0.05) decrease in portal pressure, while morphometric analysis revealed a significant reduction (P < 0.05) of all parameters studied in bosentan-treated rats, except in the total and relative number of submucosal veins.

CONCLUSIONS

Bosentan administration seemed to significantly attenuate dilation of submucosal veins in the lower esophagus of cirrhotic rats. This effect was mainly attributed to a decrease in the portal pressure induced by chronic bosentan administration.

Effects of liver fibrosis on verapamil pharmacokinetics in rats

1. Liver fibrosis is the compensatory state of cirrhosis. In the long asymptomatic period, it is imperative to select a proper dosing regimen for drugs that are applicable to hepatic fibrosis owing to altered pharmacokinetics and bioavailability. The present study was designed to observe the changes in verapamil pharmacokinetics in rats with early liver fibrosis with respect to alterations in cytochrome P450 3A (CYP3A) and P-glycoprotein (P-gp). 2. A rat liver fibrosis model was successfully established using several inducers, including a high-fat diet, alcohol and carbon tetrachloride. After rats received a single intravenous or oral dose of verapamil (5 mg/kg), the plasma concentrations of verapamil were determined at scheduled time-points using HPLC. The activity of hepatic and small intestinal microsomal erythromycin N-demethylase (a marker for CYP3A) and the expression of small intestinal cyp3a and multidrug resistance (mdr) mRNA were compared between normal rats and rats with liver fibrosis. 3. The results showed that when verapamil was administered intravenously, the area under the curve (AUC), elimination half-life (T((1/2)(K10))) and mean residence time (MRT) increased significantly, whereas clearance (Cl) decreased, in rats with liver fibrosis compared with normal rats. After oral administration of verapamil, the AUC, (T((1/2)(K10))) and maximum concentration (C(max)) increased, Cl decreased and the absorption half-life (T((1/2)(K01))) and time to peak concentration (T(max)) were unchanged compared with normal rats. The oral bioavailability of verapamil was 32.9% in normal rats and 34.4% in rats with liver fibrosis. Furthermore, decreased CYP3A activity in the liver was accompanied by upregulated cyp3a9/18 and unchanged mdr mRNA in the small intestine compared with normal rats. Expression of cyp3a9/18 and mdr mRNA in the intestine was significantly inhibited by verapamil. 4. The results suggest that the lowered Cl and increased AUC of verapamil after intravenous and oral administration in rats with liver fibrosis were due to downregulation of CYP3A in the liver. The absorption rate of verapamil in rats with liver fibrosis was unchanged because mdr was unchanged and cyp3a was inhibited in the intestine by verapamil itself. There was no notable difference in oral bioavailability between normal rats and rats with liver fibrosis.

Protective effect of verapamil on multiple hepatotoxic factors-induced liver fibrosis in rats

The purpose of the present work was to investigate the effect of verapamil on liver fibrosis induced by multiple hepatotoxic factors in rats. Male Wistar rats were divided into a normal control group, a liver fibrosis model control group, and verapamil groups with different dosages. Multiple hepatotoxic factors including carbon tetrachloride (CCl(4)), ethanol and high cholesterol were used to make the animal model of liver fibrosis. The parameters of serum l-alanine aminotransferase (ALT), liver malondialdehyde and hydroxyproline contents were measured. Samples of the liver obtained by biopsy were subjected to histological and immunohistochemical studies for the expressions of alpha-smooth muscle actin (alpha-SMA) and transforming growth factor-beta(1) (TGF-beta(1)). Results showed that verapamil induced a dose-dependent decrease of serum ALT, liver malondialdehyde and hydroxyproline compared with liver fibrosis model control. Verapamil reduced hepatocyte degeneration and necrosis, and delayed the formation of liver fibrosis. The levels of expression of alpha-SMA and TGF-beta(1) in the hepatic tissue of three of the verapamil-treated groups were significantly less than those of the liver fibrosis model control group. The results showed that verapamil acts against the formation of liver fibrosis, the mechanism might be due to a protective effect for hepatocytes and through decreasing TGF-beta(1) to block the activation of hepatic stellate cells (HSCs) and collagen gene expression.

Low-dose oral rapamycin treatment reduces fibrogenesis, improves liver function, and prolongs survival in rats with established liver cirrhosis

BACKGROUND/AIMS

Mammalian target of rapamycin (mTOR) signalling is central in the activation of hepatic stellate cells (HSCs), the key source of extracellular matrix (ECM) in fibrotic liver. We tested the therapeutic potential of the mTOR inhibitor rapamycin in advanced cirrhosis.

METHODS

Cirrhosis was induced by bile duct-ligation (BDL) or thioacetamide injections (TAA). Rats received oral rapamycin (0.5 mg/kg/day) for either 14 or 28 days. Untreated BDL and TAA-rats served as controls. Liver function was quantified by aminopyrine breath test. ECM and ECM-producing cells were quantified by morphometry. MMP-2 activity was measured by zymography. mRNA expression of procollagen-alpha1, transforming growth factor-beta1 (TGF-beta1) and beta2 was quantified by RT-PCR.

RESULTS

Fourteen days of rapamycin improved liver function. Accumulation of ECM was decreased together with numbers of activated HSCs and MMP-2 activity in both animal models. TGF-beta1 mRNA was downregulated in TAA, TGF-beta2 mRNA was downregulated in BDL. 28 days of rapamycin treatment entailed a survival advantage of long-term treated BDL-rats.

CONCLUSIONS

Low-dose rapamycin treatment is effectively antifibrotic and attenuates disease progression in advanced fibrosis. Our results warrant the clinical evaluation of rapamycin as an antifibrotic drug.

Effect of verapamil on nitric oxide synthase in a portal vein-ligated rat model: Role of prostaglandin

AIM: To investigate the effects of verapamil on nitric oxide (NO) synthesis in a portal vein-ligated rat model.

METHODS: Systemic and splanchnic hemodynamics were measured by radiolabeled microspheres in portal hypertensive rats after acute administration of verapamil (2 mg/kg) on chronic treatment with N^w–nitro-L-arginine (NNA)(80 mg/kg) and/or indomethacin (2 mg/kg) .

RESULTS: Verapamil (2 mg/kg) caused a marked fall in both arterial pressure and cardiac output accompanied by an insignificant change in the portal pressure and no change in portal venous inflow. This result suggested that verapamil did not cause a reduction in portal vascular resistance of portal hypertensive rats, which was similar between N^w- nitro–L-arginine-treated and indomethacin-treated groups.

CONCLUSION: In portal hypertensive rats pretreated with NNA and/or indomethacin, acute verapamil administration can not reduce the portal pressure, suggesting that NO and prostaglandin play an important role in the pathogenesis of splanchnic arterial vasodilation in portal hypertension.

A pilot study to investigate the use of oxpentifylline (pentoxifylline) and thalidomide in portal hypertension secondary to alcoholic cirrhosis

BACKGROUND

Tumour necrosis factor-alpha is thought to be important in the pathogenesis of portal hypertension. Oxpentifylline (pentoxifylline) and thalidomide inhibit endotoxin-induced tumour necrosis factor-alpha production in vitro.

AIMS

To assess the toxicity of oxpentifylline (pentoxifylline) and thalidomide in cirrhosis and their effect on the hepatic venous pressure gradient and tumour necrosis factor-alpha production.

METHODS

In an open-label pilot study, 20 abstinent patients with stable alcoholic cirrhosis and oesophageal varices were recruited; 12 patients completed haemodynamic measurements before and after treatment with oxpentifylline (pentoxifylline) 1800 mg (n=6) or thalidomide 200 mg (n=6) daily for 2 weeks. Tumour necrosis factor-alpha production was assessed in ex vivo monocyte cultures stimulated with endotoxin.

RESULTS

Thalidomide reduced the hepatic venous pressure gradient from 19.7 mmHg (9.3-23.5 mmHg) to 12.2 mmHg (4.7-19.5 mmHg) (P=0.03) without reducing the hepatic blood flow or altering systemic haemodynamic parameters. Thalidomide reduced ex vivo tumour necrosis factor-alpha production by approximately 50%. Oxpentifylline (pentoxifylline) had no significant effect on any of the parameters measured. Side-effects led to dose reduction or treatment withdrawal in 40% of patients.

CONCLUSION

Thalidomide, but not oxpentifylline (pentoxifylline), reduces the hepatic venous pressure gradient in stable alcoholic cirrhotics, an effect that may be mediated by the inhibition of tumour necrosis factor-alpha production. The role of tumour necrosis factor-alpha inhibitory drugs in the therapy of portal hypertension should be investigated in a randomized controlled trial.

Hemodynamic effects of synephrine treatment in portal hypertensive rats

Synephrine, a sympathomimetic alpha1-adrenoceptor agonist, has been shown to induce dose-dependent portal hypotensive effects after acute intravenous infusion. The present study was undertaken to investigate the hemodynamic effects of 8-day administration of synephrine in portal hypertensive rats. Portal hypertension was induced by either partial portal vein ligation (PVL) or bile duct ligation (BDL). Portal hypertensive rats were allocated into one of two groups: vehicle group (0.1 N HCl, 0.5 ml/12 h) or synephrine group (1 mg/kg per 12 h), with 7 rats in each group. Synephrine or vehicle was administered by gavage into PVL and BDL rats for 8 consecutive days. Systemic as well as splanchnic hemodynamic parameters were measured thereafter. Synephrine significantly ameliorated the hyperdynamic state in both PVL and BDL rats. The portal venous pressure in PVL and BDL rats (-13.5% and -10.1%, respectively), portal tributary blood flow (-19.5% and -20.4%) and cardiac index (-12.1% and -18.8%) were significantly reduced, while mean arterial pressure (10.4% and 23.4%) and systemic (26.3% and 51.0%) as well as portal territory (47.1% and 67.7%) vascular resistance were enhanced by treatment of synephrine as compared with vehicle treatment. Our results showed that eight-day administration of synephrine exerted beneficial hemodynamic effects in two models of portal hypertensive rats.

The Role of the Sinusoidal Endothelium in Liver Function

Microvascular exchange in the liver is governed by fenestrations in sinusoidal endothelial cells and can be manipulated pharmacologically. Microvascular exchange is affected in alcoholic liver disease and cirrhosis, the former leading to a loss of fenestrae, the latter to sinusoidal capillarization and thereby to loss of liver function in disease.

Effects of tetramethylpyrazine on portal hypertensive rats

The effects of tetramethylpyrazine, an alkaloid isolated from a Chinese herb Ligusticum wallichii Franch have been assessed in portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation in Sprague-Dawley rats. Two weeks after ligation, when the hyperdynamic state had stabilized, rats were anaesthetized after an overnight fast and cannulated for measurement of mean arterial pressure, portal venous pressure, cardiac index and heart rate. Tetramethylpyrazine (3.0, 9.9 and 30mgkg(-1)) induced dose-dependent reductions of portal venous pressure and mean arterial pressure after intravenous infusion. The maximum percentage reduction of portal venous pressure after tetramethylpyrazine was 6.0+/-0.8, 9.3+/-1.6 and 20+/-2% of baseline for doses of 3.0, 9.9 and 30.0mgkg(-1), respectively. Also, total peripheral resistance was significantly reduced by tetramethylpyrazine and cardiac index was slightly increased. Our results showed that tetramethylpyrazine induced portal pressure reduction in portal hypertensive rats.

The effect of endothelin and its antagonist Bosentan on hemodynamics and microvascular exchange in cirrhotic rat liver

BACKGROUND/AIMS

To characterize the effects of endothelin-1 and of Bosentan, a mixed endothelin antagonist, on hepatic hemodynamics in cirrhotic animals in vivo and on hepatic microvascular exchange in the perfused rat liver.

METHODS

Biliary cirrhosis was induced by bile duct ligation, and micronodular cirrhosis by chronic exposure to phenobarbital/CCl4 in male rats. Hepatic hemodynamics were studied under basal conditions and after administration of Bosentan (3-30 mg/kg) by the microsphere technique. Microvascular exchange was assessed in the in situ perfused rat liver by the multiple indicator dilution technique.

RESULTS

Bosentan lowered portal pressure in a dose-dependent fashion; at the highest dose tested, this decrease averaged -29+/-11 and -26+/-8% in biliary and micronodular cirrhosis, respectively (p<0.01). This was achieved mainly via a marked decrease in hepatic arterial flow. In the perfused liver, endothelin-1 induced a dose-dependent vasoconstriction; up to 10(-9) mol/l; this was not associated with any effect on viability. At this dose, endothelin-1 markedly decreased extravascular albumin space in both controls and micronodular cirrhosis; this could be antagonized by Bosentan 10(-5) mol/l.

CONCLUSIONS

Endothelin-1 affects hepatic microvascular exchange, presumably by a direct effect on hepatic sinusoidal endothelial cells. A mixed endothelin antagonist lowers portal pressure in vivo, presumably by acting on hepatic stellate cells, and counteracts the microvascular effects of endothelin-1 in vitro. These properties could prove useful in treatment of portal hypertension.

Haemodynamic effects of chronic tetrandrine treatment in portal hypertensive rats

Tetrandrine is a calcium channel antagonist with reported antihypertensive effect. However, the potential role of tetrandrine as a therapeutic agent in portal hypertension has yet to be explored. The present study aimed to investigate the haemodynamic effects of chronic tetrandrine treatment on portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation in Sprague-Dawley rats. Animals were allocated into one of two groups: a tetrandrine group and a vehicle group. Tetrandrine (20 mg/kg) or vehicle was administered by gavage every 12 h for 8 consecutive days, starting 1 day before ligation and continuing thereafter. After 8 days of tetrandrine treatment, systemic haemodynamics, organ blood flow and the degree of portal-systemic shunting were measured after an overnight fast. The portal venous pressure and protal tributary blood flow were significantly decreased, while portal territory as well as hepto-collateral vascular resistance significantly increased in the tetrandrine group compared with the vehicle group. The cardiac index was increased, while systemic vascular resistance was decreased, the the tetrandrine group. Mean arterial pressure, heart rate, portal-systemic shunting and bodyweight were similar between the two groups. Renal blood flow was decreased in the tetrandrine group. In conclusion, long-term treatment of tetrandrine reduced portal venous pressure and alleviated splanchnic hyperaemina in portal hypertensive rats without affecting the portal-systemic shunting.

Portal hypotensive effects of tetrandrine and verapamil in portal hypertensive rats

The portal hypotensive effects of tetrandrine and verapamil (both calcium-channel blockers) were assessed in portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation in Sprague-Dawley rats. Both tetrandrine (4, 8, 16 and 24 mg kg-1) and verapamil (0.5, 1.0, 1.5 and 2.0 mg kg-1) induced dose-dependent decreases of portal venous pressure and mean arterial pressure after intravenous infusion. for example, infusion of tetrandrine (16 mg kg-1) induced a maximum reduction of portal venous pressure and mean arterial pressure approximately 1 min after the start of infusion. Portal venous pressure decreased from baseline (12.5 mmHg) to 10.0 mmHg, and mean arterial pressure from baseline (90 mmHg) to 80 mmHg. Heart rate decreased from 250 to 240 beats min-1. At 24 mg kg-1, tetrandrine reduced portal venous pressure and mean arterial pressure to 20.3 +/- 2.4% and 28.4 +/- 1.4% of baseline, respectively. Our results show that both tetrandrine and verapamil induce portal pressure reduction in portal hypertensive animals.

Mechanical pumping of portal blood to the liver: hemodynamic effects of a new experimental treatment for portal hypertension

BACKGROUND/AIMS

It has been suggested that mechanical pumping of portal blood to the liver may correct portal hypertension while increasing portal flow to the liver, which may enhance liver function in cirrhosis. However, the hemodynamic effects of this procedure are unknown. The present study investigated these issues in rats with portal hypertension due to portal vein stenosis.

METHODS

Mechanical pumping of portal blood to the liver was established by an extracorporeal shunt bypassing the portal vein stenosis, connected to a continuous withdrawal/infusion pump. Portal pressure, portal-systemic shunting (mesenteric injection of Cr-51 microspheres, n = 10), mesenteric artery blood flow (perivascular Transonic flowmeter, n = 7) and systemic hemodynamics and regional blood flows (left ventricle injection of Ce-141 microspheres, n = 15), were measured at pumping rates of 0, 3 and 6 ml.min-1.

RESULTS

Mechanical pumping of portal blood to the liver caused a marked decrease in portal pressure (from 17 +/- 1 to 12.6 +/- 1 and 9.4 +/- .9 mmHg at pumping rates of 0, 3 and 6 ml.min-1) and portal-systemic shunting (from 97 +/- 4 to 70 +/- 4 and 51 +/- 6% respectively) (p < 0.001). However, there were no significant changes in mesenteric artery flow (5.5 +/- 3 vs 5.6 +/- 3 ml.min-1.100 g-1), suggesting that all blood pumped to the liver was withdrawn from that circulating through the collaterals. Moreover, there were no changes in mean arterial pressure, cardiac index, peripheral resistance and splanchnic arteriolar resistance.

CONCLUSIONS

The short-term mechanical pumping of portal blood to the liver effectively decreases portal pressure and portal-systemic shunting and has no significant effects on systemic and splanchnic hemodynamics in portal hypertensive rats.

Effect of verapamil on renal haemodynamics in a portal hypertensive rat model

In order to investigate the effects of verapamil on renal haemodynamics in rats with portal hypertension, verapamil was given at either a low (0.2 mg/kg) or high (2 mg/kg) dose to rats after portal vein ligation. An approximate 12% decrease in mean arterial pressure followed administration of low dose verapamil, with a significant decrease in cardiac output and renal blood flow, as well as reduced portal pressure, observed; these signs were all indicative of a rise in renal vascular resistance. In contrast, the marked fall in both mean arterial pressure and cardiac output with high dose verapamil, accompanied by a significant decrease in portal pressure and no change in renal blood flow, suggests a reduction in renal vascular resistance. This study shows that the acute effects of verapamil on renal haemodynamics may vary with the dose used. Also, acute verapamil administration tends to decrease renal blood flow to alter the autoregulation of the kidney; thus, caution should be taken in the clinical use of verapamil in the treatment of cirrhosis with portal hypertension.

Effects of isosorbide-5-mononitrate on variceal pressure and systemic and splanchnic haemodynamics in patients with cirrhosis

BACKGROUND

Isosorbide-5-mononitrate is a long-acting nitrovasodilator which was introduced for the treatment of portal hypertension because of its capacity to reduce portal pressure. In contrast to vasoconstrictors, isosorbide-5-mononitrate acts primarily by decreasing portal-collateral resistance without deleterious effects on liver function, although at high doses, a reflex splanchnic vasoconstriction elicited by the fall in arterial pressure may further decrease portal pressure. However, there is no information on the effects of isosorbide-5-mononitrate on variceal pressure, which is thought to be a major determinant of variceal haemorrhage.

METHODS

We investigated the effects of isosorbide-5-mononitrate (40 mg, orally; n = 12) or placebo (n = 10) on variceal pressure (non-invasive endoscopic gauge) and hepatic haemodynamics in 22 patients with cirrhosis.

RESULTS

Placebo administration had no significant effects. In contrast, isosorbide-5-mononitrate significantly reduced variceal pressure (from 13.5 +/- 3.6 to 9.8 +/- 3.2 mmHg, p < 0.005). This was associated with a fall in wedged hepatic venous pressure (from 28 +/- 5.8 to 25.9 +/- 6.2 mmHg, p < 0.005), hepatic venous pressure gradient (from 20 +/- 4 to 18 +/- 4.7 mmHg, p < 0.005) and azygos blood flow (from 668 +/- 197 to 597 +/- 160 ml/min, p < 0.05), suggesting that the decrease in variceal pressure caused by isosorbide-5-mononitrate could be caused by both reductions in collateral resistance and collateral blood flow. Isosorbide-5-mononitrate moderately reduced mean arterial pressure (-13 +/- 16%; p < 0.005), its fall being directly related to the fall in hepatic venous pressure gradient (r = 0.6, p < 0.01).

CONCLUSIONS

The results of this study show that isosorbide-5-mononitrate markedly and significantly reduces variceal pressure in patients with cirrhosis and provide further support for its clinical use in the pharmacological treatment of portal hypertension.

Continuous prazosin administration in cirrhotic patients: effects on portal hemodynamics and on liver and renal function

BACKGROUND & AIMS

Hepatic vascular resistance is influenced by alpha-adrenergic tone. The aim of this study was to investigate the effects of continuous blockade of alpha-adrenoceptors with prazosin on hemodynamics, liver function, and renal function and whether the association of propranolol or furosemide enhances the portal pressure lowering effect of prazosin.

METHODS

Cirrhotic patients with portal hypertension were studied at baseline and after a 3-month course of prazosin (n = 18) or placebo (n = 10).

RESULTS

No changes were observed in the placebo group. Prazosin decreased the hepatic venous pressure gradient (HVPG) while increasing hepatic blood flow. Liver function improved as shown by an increase in hepatic and intrinsic hepatic clearances of indocyanine green and galactose elimination capacity. A significant reduction in mean arterial pressure and systemic vascular resistance was associated with increases in plasma renin activity and aldosterone concentration and a decrease in glomerular filtration rate. The plasma volume increased significantly, and 6 patients developed edema. The association of propranolol (n = 8) but not furosemide (n = 7) to prazosin increased the reduction in HVPG and attenuated the increase in plasma renin activity.

CONCLUSIONS

In cirrhotic patients, continuous prazosin administration reduces portal pressure and improves liver perfusion and function but favors sodium and water retention. The association of propranolol enhances the decrease in portal pressure, suggesting a potential benefit from this combined therapy.

Oxygen supplementation restores theophylline clearance to normal in cirrhotic rats

BACKGROUND/AIMS

Capillarization associated with hepatic fibrosis may present a functional barrier to oxygen diffusion into the hepatocyte, and restriction on cellular oxygen supply may represent the rate-limiting constraint on hepatic oxidative drug metabolism. The aim of this study was to test this hypothesis by examining the effect of oxygen supplementation on plasma theophylline clearance in 10 control and 10 cirrhotic rats.

METHODS

Theophylline (3 mg/kg) was administered intravenously on two separate occasions, 24 hours apart, during which time the rats breathed either room air or oxygen (95%) from 1 hour before dosing until the end of plasma sampling with a randomized order of gas exposure.

RESULTS

Theophylline clearance was significantly reduced by a mean of 37% (n = 10; P = 0.003) in cirrhotic rats compared with controls. Oxygen supplementation significantly improved plasma theophylline clearance in cirrhotic rats by a mean of 40% (n = 10; P = 0.007), whereas clearance remained unchanged in healthy rats. Clearance in oxygen-supplemented cirrhotic rats was not significantly different from that in controls (P > 0.05).

CONCLUSIONS

These novel findings indicate an important role for hepatic oxygenation in improving drug disposition in cirrhosis, which may have potentially important clinical implications for the management of this disease.

Liver function improvement following increased portal blood flow in cirrhotic rats

BACKGROUND/AIMS

Liver microcirculation in cirrhosis is characterized by development of intrahepatic shunts and capillarization of sinusoids secondary to cell necrosis and deposition of new collagen, resulting in both decreased drug elimination and increased vascular resistance with portal hypertension. The aim of this study was to examine the effects of increased portal blood flow on hepatic microcirculation and drug elimination in 13 perfused livers from cirrhotic rats.

METHODS

Intrahepatic resistance was assessed under basal conditions (21.2 +/- 0.3 mL/min) and 1 hour after doubling the flow (41.6 +/- 1.0 mL/min). A multiple indicator dilution technique was used at both flow rates to measure sinusoidal volume, albumin and sucrose extravascular volumes, and cellular water volume. Hepatic elimination of labeled taurocholate and propranolol was also measured, and the recovery of 15-microns microspheres was used to evaluate large intrahepatic shunts.

RESULTS

After doubling the flow, intrahepatic resistance decreased by 31%. Sinusoidal and extravascular volume increased significantly without a change in microsphere recovery. However, there was a marked increase in taurocholate and propranolol elimination by cirrhotic livers. Moreover, during high flow, significant correlations were found between changes in albumin extravascular volume and taurocholate and propranolol elimination.

CONCLUSIONS

Increased portal blood flow in cirrhotic rats induces a decrease in intrahepatic resistance without changes in intrahepatic shunting and improves drug elimination by the liver without deleterious effects on hepatocyte viability.

Nicardipine increases hepatic blood flow and the hepatic clearance of indocyanine green in patients with cirrhosis

The present study investigated the hemodynamic effects of nicardipine, a new calcium channel blocker, and placebo in 14 patients with cirrhosis. Sixty minutes after nicardipine administration (20 mg orally; n = 8), there was a significant increase in hepatic blood flow (25 +/- 21%; p < 0.05) and azygos blood flow (33 +/- 40%; p < 0.05) but no significant change in the hepatic venous pressure gradient. As a result of the increase in hepatic blood flow and the lack of change in the hepatic venous pressure gradient, nicardipine significantly reduced hepatic sinusoidal resistance (-14 +/- 15%; p < 0.05). Enhanced liver perfusion was associated with a significant increase in the hepatic clearance of indocyanine green (from 241 +/- 81 to 265 +/- 92 ml/min, p < 0.05). A mild, well-tolerated decrease in mean arterial pressure (-10 +/- 6%, p < 0.05), without significant changes in cardiac output, systemic vascular resistance and heart rate, was also observed. Placebo administration (n = 6) did not cause significant changes in systemic or hepatic hemodynamics. The results of the present study show that nicardipine, unlike other calcium channel blockers, effectively increases hepatic blood flow and the hepatic clearance of indocyanine green in patients with cirrhosis. The acute beneficial effects of nicardipine should be confirmed in chronic studies.

Portal pumping: a new perspective for treatment of variceal hemorrhage and liver failure in end-stage cirrhosis?

In end-stage cirrhosis complicated by variceal hemorrhage, attempts to reduce portal pressure by treatments such as portosystemic shunts also decrease sinusoidal perfusion and risk impairing liver function. It has been suggested that encouraging portal flow to pass through the cirrhotic liver by mechanical action could cause a decrease in distal (splanchnic) portal pressure on one hand, and improve liver function on the other. The aim of this work was to evaluate the hemodynamic and functional effects of a 30-min pump-driven increase in portal blood flow through the liver of patients with end-stage cirrhosis before the anhepatic phase of liver transplantation. Basel portal flow (800 +/- 270 ml.min-1) was increased two fold (n = 10) or four fold (n = 9). When the flow was doubled, splanchnic portal pressure decreased 17.9 +/- 11.3% (from 31.8 +/- 5.3 to 26.0 +/- 5.8 mmHg, n = 10; p < 0.001); when flow was increased four fold, splanchnic portal pressure decreased 39.2 +/- 15.4% (from 32.8 +/- 5.0 to 19.9 +/- 6.0 mmHg, n = 9; p < 0.001). The comparison of indocyanine green clearance between basal and doubled portal flow demonstrated an increase of 32.1 +/- 26.9% (n = 5; p = 0.053). Histological analysis demonstrated sinusoidal dilatation in three out of ten livers. These results, as well as previous studies using isolated perfused cirrhotic rat or human livers, suggest that portal pumping should be explored as a treatment for certain sclerotherapy-resistant cirrhotic patients, with variceal hemorrhage and liver failure.

Pharmacological treatment of portal hypertension: hemodynamic effects and prevention of bleeding

In the past 10 years, it has been clearly shown that vasoactive substances reduce portal pressure in patients or animals with portal hypertension. Some of these substances act by inducing splanchnic vasoconstriction, while others reduce hepatic and porto-systemic collateral vascular resistance and, thus, induce a portal hypotensive effect. Still others induce arterial hypotension, which causes a vasoconstrictive effect in the splanchnic territory. Since these drugs act on different vascular receptors, their combination should have a more marked effect on portal hypertension. Up to now, only nonselective beta-blockers have been used in the prevention of first gastrointestinal bleeding in patients with portal hypertension and esophageal varices and in the prevention of recurrent gastrointestinal bleeding. These trials have shown that propranolol or nadolol significantly reduce either a first episode of bleeding or recurrent bleeding. This pharmacological treatment also improves the survival rate in these patients. All of these studies have helped us to understand, in part, why gastrointestinal hemorrhage occurs in certain patients. Additional studies of beta-blockers or other substances are, nevertheless, necessary to select patients who will respond to this type of treatment. Finally, it is possible that the pharmacological treatment of portal hypertension may also be used before esophageal varices occur.

Effects of vasopressin and nicardipine on hemodynamics and liver function in patients with cirrhosis: comparison with vasopressin alone

The effects of a combination of vasopressin and a calcium channel blocker (nicardipine) on portohepatic hemodynamics and liver function were compared with the effects of vasopressin alone in 18 patients with portal hypertension. Nine patients received 0.4 units/min of vasopressin and 9 patients received the same dose of vasopressin plus 0.3 mg/min of nicardipine for 40 min. Vasopressin plus nicardipine induced a significant reduction in both free portal venous pressure and the portal venous pressure gradient. These effects were similar to the changes with vasopressin alone (-14% vs. -16% in free portal venous pressure; -29% vs. -31% in portal venous pressure gradient). Vasopressin decreased both hepatic blood flow (-34%, P < 0.01) and intrinsic clearance of indocyanine green (-22%, P < 0.05). In contrast, these two parameters did not significantly change after vasopressin plus nicardipine (-8% and -3%, respectively). These results suggest that the addition of nicardipine improves hepatic impairment induced by vasopressin but causes no further reduction on portal pressure.

Effects of molsidomine, a long acting venous dilator, on portal hypertension. A hemodynamic study in patients with cirrhosis

The present study investigated the effects of molsidomine, a predominant venous dilator which, contrary to organic nitrates, does not produce pharmacological tolerance on splanchnic and systemic hemodynamics in patients with cirrhosis. Twenty-seven cirrhotic portal hypertensive patients were studied prior to and up to 2 h after the oral administration of 2 mg of molsidomine (n = 11), 4 mg of molsidomine (n = 8) or placebo (n = 8). Molsidomine caused a significant reduction in the hepatic venous pressure gradient. The mean decrease at 60 min was -6.8 +/- 9% after 2 mg (p less than 0.05) and -15.4 +/- 12% after 4 mg (p less than 0.01). The decrease in the hepatic venous pressure gradient was maintained at 120 min: -11% after 2 mg (p less than 0.05) and -19% with 4 mg (p less than 0.01). This was associated with mild changes in azygos blood flow and with a significant decrease in hepatic blood flow (-17%, p less than 0.05). There was a moderate reduction in mean arterial pressure (-12.6% after 2 mg and -13.2% after 4 mg, p less than 0.01), which was due to a reduction in cardiac output, without any significant fall in systemic vascular resistance. Placebo administration did not change systemic or hepatic hemodynamics. This study shows that molsidomine causes a significant and sustained reduction in portal pressure in patients with cirrhosis, suggesting the potential role of this agent in the treatment of portal hypertension.

Detoxification of soman in the perfused rat liver: quantitative uptake and stereoisomer metabolism

The detoxification of soman (1,2,2-dimethyl-propyl methylphosphonofluoridate) was measured in rat livers, using hemoglobin-free, non-recirculating perfusion in situ. Since the detoxification processes may differ in perivenous and periportal zones of liver parenchyma, soman uptake, stereoselective metabolism and inhibition of esterases were compared in antegrade and retrograde perfusion experiments. At low concentrations of soman (up to about 10 mumol l-1 for 5 min) soman was taken up by the liver nearly quantitatively. About 5% recovery rate in the perfusate corresponded well to the intrahepatic shunt flow. Infusions of higher amounts yielded increasing recovery rates. The racemic infusion medium contained the four isomers of soman, C(-)P(-) to C(+)P(+), in nearly identical amounts, whereas in the effluent perfusate only P(-) isomers were found. Even small amounts of soman (5-120 nmol g-1 liver wet weight) caused significant inhibition of hepatic aliesterase activity. Doses higher than 200 nmol g-1 suppressed esterase activity by more than 90%. No essential differences in soman uptake, stereoselective metabolism or inhibition of esterases were found between antegrade and retrograde perfusion experiments.

Lack of effect of verapamil and isosorbide dinitrate on the hepatic clearance of indocyanine green in cirrhosis

1. Vasodilators are currently under investigation as possible therapeutic agents in the treatment of portal hypertension. Among them calcium-channel antagonists and organic nitrates have been of particular interest. Few and conflicting data, however, have been reported on their effect on liver function. 2. Twenty patients with biopsy-proven alcoholic cirrhosis were studied before and 25-35 min following the acute administration of 5 mg verapamil i.v. (eight patients) or 5 mg isosorbide dinitrate sublingually (12 patients). The plasma clearance of indocyanine green (ICG) and its intrinsic hepatic clearance were used as indices of liver function. Seven further patients were investigated before and after a placebo infusion according to the same methodology. 3. No significant change in ICG kinetics was found after verapamil or isosorbide dinitrate.

Effect of verapamil on splanchnic haemodynamics in a portal hypertensive rat model

To elucidate the effects of verapamil on splanchnic haemodynamics in rats with portal hypertension, verapamil was given at a low dose (0.2 mg/kg) and a high dose (2 mg/kg) to the rat model after portal vein ligation. Approximately 10% decrease in arterial pressure was caused by the low dose of verapamil, with significant decreases in cardiac output and portal venous inflow as well as reduced portal pressure; these were all indicative of a rise in portal vascular resistance. In contrast, the marked fall in both arterial pressure and cardiac output in the high dose, accompanied by a significant decrease in the portal pressure and the unchanged portal venous inflow, suggested a reduction in portal vascular resistance. This study shows that the acute effects of verapamil on portal hypertension may vary with the dosage used. These results also demonstrate that, since the therapeutic efficacy and safety of verapamil is only in a very limited range of dose, caution should be taken in its clinical use in the treatment of cirrhosis with portal hypertension.

Hepatic circulation: potential for therapeutic intervention

In recent years, knowledge of the physiology and pharmacology of hepatic circulation has grown rapidly. Liver microcirculation has a unique design that allows very efficient exchange processes between plasma and liver cells, even when severe constraints are imposed upon the system, i.e. in stressful situations. Furthermore, it has been recognized recently that sinusoids and their associated cells can no longer be considered only as passive structures ensuring the dispersion of molecules in the liver, but represent a very sophisticated network that protects and regulates parenchymal cells through a variety of mediators. Finally, vascular abnormalities are a prominent feature of a number of liver pathological processes, including cirrhosis and liver cell necrosis whether induced by alcohol, ischemia, endotoxins, virus or chemicals. Although it is not clear whether vascular lesions can be the primary events that lead to hepatocyte injury, the main interest of these findings is that liver microcirculation could represent a potential target for drug action in these conditions.

Verapamil has no effect on porto-hepatic pressure gradient, hepatic blood flow and elimination function of the liver in patients with liver cirrhosis

This study aimed to assess the effects of verapamil, a calcium-channel blocker, on porto-hepatic pressure gradient and on hepatic function as measured by the intrinsic hepatic clearance of indocyanine green (ICG) in patients with biopsy proven alcoholic cirrhosis. Hepatic venous pressures and hepatic extraction of ICG were measured before and 60 min after intravenous injection of 10 mg of verapamil in 19 consecutive patients. Hepatic blood flow and intrinsic hepatic clearance of ICG were calculated in the 10 patients whose hepatic extraction fraction was higher than 10%. No significant difference was observed when comparing porto-hepatic pressure gradient (17.72 +/- 4.79 vs. 17.77 +/- 4.43 mmHg), hepatic blood flow (13.47 +/- 4.75 vs. 16.13 +/- 7.88 ml.min-1.kg-1) and intrinsic hepatic clearance of ICG (1.99 +/- 0.54 vs. 1.97 +/- 0.45 ml.min-1.kg-1) before and after verapamil injection. We conclude that verapamil has no beneficial effect in patients with alcoholic cirrhosis.

Reduction of portal pressure by isosorbide-5-mononitrate in patients with cirrhosis. Effects on splanchnic and systemic hemodynamics and liver function

The results of a study to characterize the effects of the oral administration of isosorbide-5-mononitrate (Is-5-Mn), the active metabolite of isosorbide dinitrate, on portal hypertension in 23 patients with cirrhosis are reported. Patients received 20 mg of Is-5-Mn (n = 10), 40 mg (n = 9), or a placebo (n = 4). No significant changes were observed after the administration of the placebo. However, both doses of Is-5-Mn significantly reduced portal pressure, as evaluated by measurements of the hepatic venous pressure gradient. The fall in portal pressure averaged 10% after the 20-mg dose and 18% after 40 mg and was maintained for the 2 h of observation. Reduction of portal pressure was due to a decrease in the wedged hepatic vein pressure, with no changes in the free hepatic venous pressure. After the 20-mg dose, the decrease in portal pressure was associated with an increase in hepatic blood flow (16%), suggesting a fall in hepatic vascular resistance. However, after the 40-mg dose, a reflex splanchnic vasoconstriction elicited by the fall in arterial pressure (-19%) appeared to contribute to the greater reduction in portal pressure, as suggested by a significant decrease in azygos blood flow (-15%). These beneficial effects on portal pressure were not associated with adverse effects on liver function, as evaluated by measurements of the hepatic clearance of indocyanine green and the hepatic intrinsic clearance. Neither dose of Is-5-Mn caused significant changes in these quantitative parameters of liver function. These findings suggest that Is-5-Mn could be a potentially useful and safe agent in the treatment of portal hypertension.

Combination of ketanserin and verapamil or propranolol in patients with alcoholic cirrhosis: search for an additive effect

Drugs reported to reduce portal pressure through different mechanisms were combined in the hope of either additive portal hypotensive effects in "responders," or inducing a portal hypotensive effect in "nonresponders" to the initial drug. Seven patients with alcoholic cirrhosis received verapamil, 10 mg i.v., and, 60 min later, ketanserin, 5 mg i.v. Verapamil decreased heart rate and increased free hepatic venous pressure but had no effect on hepatic venous pressure gradient or azygos blood flow. When combined with verapamil, ketanserin significantly diminished wedged hepatic venous pressure and hepatic venous pressure gradient. Ten other patients with alcoholic cirrhosis received propranolol, 15 mg i.v., and 45 min later, ketanserin, 5 mg i.v. In all patients, heart rate, cardiac index and azygos blood flow significantly decreased after propranolol. After propranolol alone, however, wedged hepatic venous pressure decreased in only five patients, responders. In five other patients, defined as nonresponders, propranolol did not decrease this pressure. The addition of ketanserin to propranolol induced further significant reduction in wedged hepatic venous pressure, hepatic venous pressure gradient and azygos blood flow. Among the five nonresponders, three had a reduced wedged hepatic venous pressure after ketanserin was combined. We conclude that verapamil does not reduce portal pressure or collateral blood flow in patients with alcoholic cirrhosis. The splanchnic hemodynamic effects of propranolol and ketanserin appear to be independent and additive, without significant systemic alteration.

The calcium-channel blocker, verapamil, does not improve portal pressure in patients with alcoholic cirrhosis

1. Recently the calcium-channel blocker, verapamil, has been reported to decrease portal pressure in rats with experimental cirrhosis and in patients with liver cirrhosis. 2. In eight patients with alcoholic cirrhosis the effect of verapamil (5 mg i.v.) on systemic and splanchnic haemodynamics was investigated. 3. Mean arterial pressure, wedged hepatic venous pressure, hepatic venous pressure gradient, and verapamil plasma concentrations were measured before and at 10, 20, 30 min following 5 mg i.v. administration of verapamil. At 30-40 min cardiac output, systemic vascular resistance and hepatic blood flow were also measured. 4. Verapamil plasma concentrations averaged 47.9 +/- 52.0, 36.5 +/- 36.3, 31.3 +/- 33.9 ng ml-1 at 10, 20, 30 min respectively: mean arterial pressure and systemic vascular resistance decreased significantly (-9% and -14% respectively), and cardiac index increased significantly (+8%). Wedged hepatic venous pressure and hepatic venous pressure gradient remained unchanged, variations never exceeding 0.2 kPa. Hepatic blood flow increased significantly by 12%. 5. These results show that i.v. administration of 5 mg verapamil does not decrease portal pressure in alcoholic cirrhosis. This lack of effect is probably the consequence of a balance between decrease in porto-hepatic vascular resistance and increase in splanchnic blood inflow.

Effects of verapamil on hepatic and systemic hemodynamics and liver function in patients with cirrhosis and portal hypertension

The effects of verapamil on hepatic and systemic hemodynamics and on liver function were investigated in 10 patients with portal hypertension due to advanced micronodular cirrhosis to verify whether, as it has been suggested, this calcium channel blocker may improve liver function and reduce portal pressure in these patients. The oral administration of 100 mg of verapamil caused systemic vasodilation, evidenced by a significant reduction in mean arterial pressure (-8.1 +/- 7.6%, p less than 0.025) and systemic vascular resistance (-12.5 +/- 9.5%, p less than 0.001), and increased heart rate (+13.9 +/- 10.4%, p less than 0.01). However, no beneficial effect was noted on portal pressure evaluated by hepatic vein catheterization (baseline 19.8 +/- 4.0, verapamil 20.2 +/- 3.6 mmHg, NS), hepatic blood flow (1.45 +/- 0.64 vs. 1.47 +/- 0.62 liters per min, NS) and hepatic vascular resistance (1.314 +/- 611 vs. 1,266 +/- 513 dyn per sec per cm-5, NS). Similarly, no change was observed in portal blood flow, measured in six patients by pulsed Doppler flowmeter (0.94 +/- 0.30 vs. 0.89 +/- 0.35 liter per min, NS). In addition, verapamil did not increase the hepatic intrinsic clearance of these patients (0.20 +/- 0.07 vs. 0.19 +/- 0.06 liter per min, NS). This study suggests that verapamil is of no beneficial effect in patients with advanced cirrhosis of the liver.

Aminopyrine N-demethylation by rats with liver cirrhosis. Evidence for the intact cell hypothesis. A morphometric-functional study

The intact cell hypothesis states that a reduced number of intrinsically normal hepatocytes, together with hemodynamic alterations, explains decreased drug metabolism in cirrhosis. We explored this hypothesis by comparing results of the aminopyrine breath test with in vitro measurements of aminopyrine N-demethylation and morphometrically determined liver cell volume in a rat model of cirrhosis. Aminopyrine N-demethylation in vivo (ABT-k) was 0.98 +/- 0.10/h (mean +/- SD) in controls. The cirrhotic rats were separated into those with normal (NCR) and those with abnormal ABT-k (PCR). Microsomal aminopyrine N-demethylase averaged 2.08 +/- 0.77 and 2.09 +/- 0.54 mumol/min in controls and NCRs, respectively; it was reduced to 1.00 +/- 0.81 mumol/min (p less than 0.02) in PCRs. Morphometrically determined hepatocellular volume was 18.8 +/- 2.8, 17.1 +/- 1.9, and 11.6 +/- 6.1 ml in controls, NCRs, and PCRs, respectively, PCRs being lower than controls (p less than 0.01) and NCRs (p less than 0.05). When N-demethylase and cytochrome P450 were related to hepatocellular volume (in milliliters), no significant difference between the three groups was apparent. We conclude that reduced aminopyrine N-demethylation in progressed cirrhosis is mainly due to a loss of liver cell volume. The function per liver cell volume remains constant, however, thus favoring the intact cell hypothesis for the handling of slowly metabolized compounds such as aminopyrine.