Bile Flow Rate Research Articles

Data for Physiologically Based Pharmacokinetic Modeling in Neonatal Animals: Physiological Parameters in Mice and Sprague-Dawley Rats

ABSTRACTRecent scientific and policy initiatives have resulted in increased interest in risk to fetuses, infants, and children and consideration of how such risks should be evaluated. A useful way of addressing this issue is to use physiologically based pharmacokinetic (PBPK) models to compare the tissue dose that children and adults receive for a given amount of a chemical ingested or inhaled. The response in children and adults for a given tissue dose can also be compared. To aid in the development of age-specific PBPK models for experimental animals, we have collected information on physiological parameters in neonates and young animals, through 60 days of age. Our effort focused on generic physiological values, such as tissue weight (termed tissue volume in the context of PBPK modeling), intake (alveolar ventilation, food intake, water intake), and flows (blood flows to tissues, bile flow, creatinine clearance, and glomerular filtration rate). To date, parameters for Sprague-Dawley rats and mice of mu...

Induction of cholestasis in the perfused rat liver by 2-aminoethyl diphenylborate, an inhibitor of the hepatocyte plasma membrane Ca2+ channels.

An increase in the cytoplasmic free Ca2+ concentration in hepatocytes as a result of the release of Ca2+ from intracellular stores and Ca2+ inflow from the extracellular space is a necessary part of the mechanism by which bile acids are moved along the bile cannaliculus by contraction of the cannaliculus. 2-Aminoethyl diphenylborate (2-APB) is a recently discovered inhibitor of store-operated plasma membrane Ca2+ channels in hepatocytes. The aim of the present study was to test the ability of 2-APB to inhibit bile flow. Bile flow was measured in the isolated perfused rat liver using cannulation of the common bile duct. Measurements were carried out in the presence or absence of 2-APB in either the presence of taurocholic acid (to enhance basal bile flow) or in the absence of taurocholic acid and in the presence of the hormones vasopressin and glucagon, which are known to stimulate bile flow. In livers perfused in the presence of taurocholic acid, 2-APB reversibly inhibited bile flow with a slow time of onset. The time of onset of inhibition was reduced by prior addition of the endoplasmic reticulum (Ca(2+) + Mg2+)adenosine triphosphatase inhibitor, 2,5-di-t-butylhydroquinone. In livers perfused in the absence of taurocholate, 2-APB had little effect on the basal rate of bile flow, but inhibited the ability of vasopressin and glucagon to stimulate bile flow. It is concluded that an inhibitor of hepatocyte plasma membrane Ca2+ channels can induce cholestasis. The results provide evidence that suggests that, over a period of time, the normal function of hepatocyte store-operated Ca2+ channels is required to maintain bile flow. Future strategies directed at the regulation of bile flow might include pharmacological or other interventions that modulate Ca2+ inflow to hepatocytes.

Mrp2 is involved in benzylpenicillin-induced choleresis.

Benzylpenicillin (PCG; 180 micromol/kg), a classic beta-lactam antibiotic, was intravenously given to Sprague-Dawley (SD) rats and multidrug resistance-associated protein 2 (Mrp2)-deficient Eisai hyperbilirubinemic rats (EHBR). A percentage of the [(3)H]PCG was excreted into the bile of the rats within 60 min (SD rats: 31.7% and EHBR: 4.3%). Remarkably, a transient increase in the bile flow ( approximately 2-fold) and a slight increase in the total biliary bilirubin excretion were observed in SD rats but not in the EHBR after PCG administration. This suggests that the biliary excretion of PCG and its choleretic effect are Mrp2-dependent. Positive correlations were observed between the biliary excretion rate of PCG and bile flow (r(2) = 0.768) and more remarkably between the biliary excretion rate of GSH and bile flow (r(2) = 0.968). No ATP-dependent uptake of [(3)H]PCG was observed in Mrp2-expressing Sf9 membrane vesicles, whereas other forms of Mrp2-substrate transport were stimulated in the presence of PCG. GSH efflux mediated by human MRP2 expressed in Madin-Darby canine kidney II cells was enhanced in the presence of PCG in a concentration-dependent manner. In conclusion, the choleretic effect of PCG is caused by the stimulation of biliary GSH efflux as well as the concentrative biliary excretion of PCG itself, both of which were Mrp2 dependent.

Pronlonged hypothermic machine perfusion preserves hepatocellular function but potentiates endothelial cell dysfunction in rat livers.

Although hypothermic machine perfusion (HMP) preservation has been shown to improve organ function and to expand the organ donor pool, problems still exist with the current HMP technology for liver preservation. The present study was conducted to investigate endothelial and hepatocellular functions following extended HMP (> r =24 hr) in rat liver model. Following 24-hour hypothermic HMP with University of Wisconsin (UW) solution or 24-hour simple cold storage (SCS), livers were reperfused with Krebs-Henseleit buffer solution at 37 degree C for 30 minutes. Hepatocyte damage and function were assessed by measuring lactate dehydrogenase (LDH) activity, bile production, and indocyanine green (ICG) extraction. Sinusoidal endothelial cell (SEC) function and permeability were determined by hyaluronic acid (HA) uptake and multiple indicator dilution (MID) method, respectively. After 24-hour hypothermic preservation, HMP livers showed lower released LDH levels, higher bile flow rate, and greater hepatic ICG uptake compared with SCS livers. However, LDH levels became significantly higher in HMP than in SCS after 30 minutes of warm perfusion. The increased enzyme levels were accompanied by a significant increase in endothelial permeability to albumin and a decrease in hyaluronic acid uptake in HMP compared to SCS. Liver wet/dry weight ratio confirmed a greater edema in HMP livers than SCS livers. These results suggest that 24-hour hypothermic HMP may help preservation of hepatocyte function, but endothelial cell dysfunction during the cold preservation may play a key role in hepatocyte dysfunction and parenchymal cell death upon reperfusion.

The effects of vascular bed expansion in steatotic rat liver graft viability.

Disturbed microcirculation caused by fat accumulation in hepatocytes has been implicated in poor graft preservation and reperfusion. The aim of this study was to investigate the effect of vascular bed expansion (VBE) during cold preservation in graft survival Moderate liver steatosis in male Wistar rats (240-280 g) was induced by choline-deficient diet. Normal, steatotic or VBE-pretreated steatotic grafts were transplanted after 1 h or 9 h of cold preservation. Graft viability was determined by 7-day survival, serum liver enzymes, plasma tumour necrosis factor (TNF)-alpha, interleukin (IL)-6, and malondialdehyde (MDA) levels. Post-reperfusion bile flow and liver histology were also examined. After 9 h of preservation, VBE-pretreated steatotic liver grafts were associated with significantly reduced serum liver enzyme, plasma TNF-alpha, IL-6, and MDA levels, as well as increased bile flow and higher survival rates compared with untreated ones. The present study shows that VBE protects fatty liver grafts from subsequent long-term cold preservation and reperfusion injury in a rat liver transplantation model.

Five- and 10-year survival rates after surgery for biliary atresia: a report from the Japanese biliary atresia registry

Purpose The aim of this study was to elucidate the epidemiology and short- and long-term results of biliary atresia in Japan analyzing the data of the Japanese Biliary Atresia Registry (JBAR). Methods In 1989, the Japanese Biliary Atresia Society started a nationwide registry, JBAR, to investigate all aspects of biliary atresia. A total of 1,381 patients, 863 girls, 507 boys, and 11 unknown, were registered between 1989 and 1999. JBAR includes an initial and follow-up questionnaires. Using these patients’ data, the incidence, sex distribution, associated anomalies, the type of obstruction, the type of operation, and the surgical results were evaluated. The 5- and the 10-year results of 735 patients who were registered initially in or before 1994 also were analyzed. Results The incidence of biliary atresia was 1 in 9,640 live births. One hundred sixty-four patients (11.9%) had type I atresia of the common bile duct, 34 (2.5%) had type II atresia of the hepatic ducts, and 1,162 (84.1%) had type III atresia at the porta hepatis. Congenital associated anomalies were found in 19.6% of the patients including 33 cases associated with polysplenia. Impact of the age at operation on bile flow was not clear until 90 days of age, and after 90 days the bile flow rate worsened. The original Roux-en-Y procedure had been used in more than 50% of the patients since 1995. In 1999, 96% of the patients underwent the original Roux-en-Y procedure or the Roux-en-Y with an intestinal valve, and only 3 patients (3.5%) underwent other modifications. There were no significant differences in either the rate of disappearance of jaundice or the incidence of cholangitis among these 3 procedures. Of the 735 patients registered in or before 1994, 19 patients (2.6%) were lost to follow-up. The 5-year survival rates of patients registered in 1989, 1990, 1991, 1992, 1993, and 1994 were 62%, 64.5%, 61.3%, 59.0%, 58.7%, and 52.7% without liver transplantation (LTx), and 69.4%, 74.2%, 75.2%, 79.5%, 78%, and 78.3% with LTx, respectively. Although the overall 5-year survival rate changed from 69.4% to 78.3%, the difference was not statistically significant. According to the 10-year follow-up results of the 108 patients initially registered in 1989, 72 (66.7%) and 57 (52.8%) survived with and without the aid of LTx, respectively. Conclusions The overall 5- and 10-year survival rates were 75.3% (553 of 734) and 66.7% (72 of 108), respectively. In spite of the increasing number of survivors after LTx, there was no significant improvement in the 5-year survival rate. It was shown that the JBAR system was functioning well with only 19 patients lost to follow-up among the 743 patients registered from 1989 to 1994.

Insulin-like growth factor-I enhances choleretic action of FK506 in rats

FK506 is an immunosuppressant for organ transplantation in the same clinical settings as cyclosporine (CsA). In the management of liver transplantation, FK506 has advantages over CsA, in terms of rejection and corticosteroid requirements. Recent clinical findings in liver transplant patients indicate that FK506, but not CsA, stimulates choleresis, suggesting that FK506 treatment may accelerate recovery from cholestatic dysfunction through its choleretic action. Recently, we demonstrated in rats that exogenous treatment with insulin-like growth factor I (IGF-I) results in an increase in bile flow and also that FK506 has the potential to increase hepatic production of IGF-I. However, circulating levels of IGF-I in FK506-treated rats were only 30% higher than in nontreated rats. In this study, we evaluated the combined effect of treatment with both IGF-I and FK506 on bile flow in rats to explore the possibility that combination treatment in liver transplant patients could enhance the choleretic action of FK506, benefiting the transplanted liver. Combination treatment of IGF-I with FK506 resulted in a potent and long-lasting increase in bile flow. Overall, this study demonstrated that IGF-I treatment enhanced the choleretic action of FK506, providing potential clinical utility for combination therapy using these two drugs, in treatment after liver transplantation.

Chronic Staphylococcal enterotoxin B and lipopolysaccharide induce a bimodal pattern of hepatic dysfunction and injury.

To determine the effect of chronic exposure to endotoxin (lipopolysaccharide) and Staphylococcal enterotoxin B on hepatic injury and function. Prospective, controlled trial. Research laboratory in a university hospital. Male Sprague-Dawley rats weighing 325-350 g with chronic vascular and bile catheters. Chronically catheterized rats were treated daily with saline, 50 microg/kg Staphylococcal enterotoxin B alone, 1000 microg/kg lipopolysaccharide alone, 1000 microg/kg lipopolysaccharide with 50 microg/kg Staphylococcal enterotoxin B, or 100 microg/kg lipopolysaccharide with 50 microg/kg Staphylococcal enterotoxin B for 10 days. Serum and biliary measures of hepatic injury and dysfunction were measured before and then 6 hrs and 1, 2, 3, 7, and 10 days after the start of treatment. The animals were killed at 10 days and the livers examined histologically. Mean rates of bile flow, biliary indocyanine green excretion, and bile acid flux were significantly decreased immediately after treatment (6 hr, 1 and 2 days) and then at 10 days. Increases in biliary and serum gamma-glutamyltransferase and serum bile acids also occurred in a similar bimodal pattern. Animals treated with lipopolysaccharide or Staphylococcal enterotoxin B alone became tolerant and did not develop the bimodal pattern of hepatic dysfunction. Histologic examination of the liver at 10 days revealed periportal inflammation and fibrosis. The combination of lipopolysaccharide and Staphylococcal enterotoxin B leads to late liver injury, whereas either toxin alone does not. These data may explain the frequent development of liver dysfunction in patients exposed to multiple bacterial toxins such as in sepsis, multiple-system organ failure, and other diseases with altered intestinal permeability.

Differences in Biliary Lipid Excretion after Major Hepatectomy in Obstructive Jaundiced Rats with Preoperative Internal, External, or No Biliary Drainage

Necessity of preoperative biliary drainage for patients with obstructive jaundice is still controversial. We recently reported that liver regeneration after major hepatectomy was better restored in a rat model of obstructive jaundice with preoperative internal biliary drainage than that without biliary drainage or with external biliary drainage. The aim of this study was to investigate the differences in biliary lipid excretion after hepatectomy in obstructive jaundiced rats with or without preoperative internal or external biliary drainage. After bile duct ligation for 7 days, rats were randomly divided into the three groups; obstructive jaundice-hepatectomy (OJ-Hx), internal biliary drainage-hepatectomy (ID-Hx), and external biliary drainage-hepatectomy (ED-Hx) groups. 70% hepatectomy and internal biliary drainage were carried out 7 days after biliary decompression in the latter two groups and without biliary decompression in the OJ-Hx group. On the day of and on days 1, 2, 3 and 7 after hepatectomy, the liver weight, DNA synthesis rate, biliary lipids excretion rates, and bile acid composition were determined. In the ID-Hx group, the DNA synthesis rate and relative liver weight were significantly higher than those of the OJ-Hx and ED-Hx groups. The excretion rates of biliary lipids were disturbed in the ED-Hx group compared with those in the ID-Hx group and the values in the OJ-Hx group were in-between the ID-Hx and ED-Hx group. The liver regeneration rate was significantly correlated with bile flow and excretion rates of biliary lipids. The maintenance of enterohepatic circulation of biliary lipids before hepatectomy may be important for the liver regeneration.

Relation of biliary bile acid output to hepatic adenosine triphosphate level and biliary indocyanine green excretion in humans.

We have previously demonstrated that there are two subgroups of patients with different types of biliary bile acid output after relief of obstructive jaundice by percutaneous transhepatic biliary drainage (PTBD). The reason for two groups is not clear but is possibly the difference in hepatic reserve function. The aim of this study was to examine the relation of biliary bile acid output to the hepatic ATP level and biliary excretion rate of indocyanine green (ICG) in humans. Patients whose bile could be collected through a PTBD tube participated in this study. The mean serum total bilirubin concentration was 12.7 mg/dl at the time of PTBD, decreasing to 1.1 mg/dl before surgery. These patients underwent curative resection for cancer of the bile duct, duodenal papilla, or pancreatic head after the relief of hyperbilirubinemia. Bile was collected at 1-hour intervals for 5 hours after intravenous administration of ICG (0.5 mg/kg) within a few days before surgery, and a small liver tissue sample was obtained immediately after laparotomy without using ischemic procedures. The concentrations of total bile acid and ICG in bile, the bile flow rate, and the bile acid output and ICG excretion rate in bile over 5 hours were determined. ATP concentrations in liver tissue were determined by high performance liquid chromatography. Results of hepatic ATP levels were correlated with the bile acid output and ICG excretion rate into bile. Both the biliary bile acid output (micromoles per 5 hours) and ICG excretion rate (percent of injected dose of ICG) over 5 hours were significantly correlated with the hepatic ATP level (p = 0.0190 and p = 0.0084, respectively). Neither the bile flow rate nor the serum liver function tests were related to the hepatic ATP level. Significant correlation was found between the bile acid output and the ICG excretion rate (p = 0.0127). Biliary bile acid output reflects the hepatic ATP level. Determination of the biliary bile acid output and ICG excretion may provide useful parameters for evaluating the hepatic energy status, which is essential for organ viability.

Increase in bile flow and biliary excretion of glutathione-derived sulfhydryls in rats by drug-metabolizing enzyme inducers is mediated by multidrug resistance protein 2.

Glutathione (GSH) is an important cellular constituent for normal liver homeostasis. Certain drug-metabolizing enzyme inducers (i.e., phenobarbital [PB] and pregnenolone-16alpha-carbonitrile [PCN]) increase biliary excretion of GSH-derived sulfhydryls (SH) as well as bile flow, whereas other drug-metabolizing enzyme inducers (i.e., 3-methylcholanthrene [3MC] and benzo(a)pyrene [BaP]), do not. The purpose of the study was to determine whether rat multidrug resistance protein 2 (Mrp2) is the inducible transporter responsible for increasing biliary SH excretion and bile flow. Sprague-Dawley (SD) rats were injected ip daily for 4 days with PB, PCN, 3MC, BaP, or vehicle; Mrp2-null Eisai hyperbilirubinemic (EHBR) rats were injected ip daily for 4 days with PCN or vehicle. Although no drug-metabolizing enzyme inducer altered hepatic GSH in SD rats, PB and PCN significantly increased the rate of biliary SH excretion and bile flow. Neither 3MC nor BaP affected the biliary SH excretion rate or bile flow. In control EHBR rats, despite elevated hepatic GSH, the rate of biliary SH excretion was almost completely eliminated and bile flow was dramatically reduced compared with SD rats. Furthermore, PCN treatment did not affect bile flow or the biliary SH excretion rate in EHBR rats. PB and PCN also increased Mrp2 protein levels, but 3MC and BaP did not. None of the drug-metabolizing enzyme inducers tested significantly increased Mrp2 mRNA levels. PCN increased Mrp2 protein, but not Mrp2 mRNA, in a time-dependent manner. In conclusion, Mrp2 is the inducible efflux transporter responsible for increased biliary SH excretion and bile flow after administration of some drug-metabolizing enzyme inducers.

Evaluation of role of bile flow patterns in process of in vitro stent occlusion.

Stent placement above the sphincter of Oddi might have advantages over stent placement across the sphincter of Oddi in prolonging stent patency in the treatment for malignant obstructive jaundice. To evaluate the role of bile flow patterns corresponding to biliary stent positioning in the process of stent occlusion in an in vitro bile perfusion model, one group of polyethylene stents was perfused continuously and another group of stents was perfused with additional flushing three times a day, simulating gallbladder emptying. After 8 weeks, the flow rates through the perfused stents were measured for evaluating the extent of stent occlusion indirectly. The results showed that bile flow rate of stents with additional flushing was significantly higher than the continuously perfused stents (P < or = 0.01). It was demonstrated that after 18 hr of perfusion, additional flushing obviously decreased bacterial adherence to stent when compared to continuously perfused stents. In conclusion, flushing of bile may decrease the build-up of substance in vitro and thus improve stent flow rates, for which decreasing bacterial adherence to stents may be responsible.

Disruption of the Sterol Carrier Protein 2 Gene in Mice Impairs Biliary Lipid and Hepatic Cholesterol Metabolism

Hepatic up-regulation of sterol carrier protein 2 (Scp2) in mice promotes hypersecretion of cholesterol into bile and gallstone formation in response to a lithogenic diet. We hypothesized that Scp2 deficiency may alter biliary lipid secretion and hepatic cholesterol metabolism. Male gallstone-susceptible C57BL/6 and C57BL/6(Scp2(-/-)) knockout mice were fed a standard chow or lithogenic diet. Hepatic biles were collected to determine biliary lipid secretion rates, bile flow, and bile salt pool size. Plasma lipoprotein distribution was investigated, and gene expression of cytosolic lipid-binding proteins, lipoprotein receptors, hepatic regulatory enzymes, and intestinal cholesterol absorption was measured. Compared with chow-fed wild-type animals, C57BL/6(Scp2(-/-)) mice had higher bile flow and lower bile salt secretion rates, decreased hepatic apolipoprotein expression, increased hepatic cholesterol synthesis, and up-regulation of liver fatty acid-binding protein. In addition, the bile salt pool size was reduced and intestinal cholesterol absorption was unaltered in C57BL/6(Scp2(-/-)) mice. When C57BL/6(Scp2(-/-)) mice were challenged with a lithogenic diet, a smaller increase of hepatic free cholesterol failed to suppress cholesterol synthesis and biliary cholesterol secretion increased to a much smaller extent than phospholipid and bile salt secretion. Scp2 deficiency did not prevent gallstone formation and may be compensated in part by hepatic up-regulation of liver fatty acid-binding protein. These results support a role of Scp2 in hepatic cholesterol metabolism, biliary lipid secretion, and intracellular cholesterol distribution.

Contribution of Serotonin to Liver Injury Following Canine Small-Intestinal Ischemia and Reperfusion

Intestinal ischemia and reperfusion (I/R) has been shown to be associated with multiple organ damages. Serotonin (5-hydroxytriptamine; 5-HT), which is synthesized in the enterochromaffin cells in the intestine and stored in platelets, is known to play an important role in platelet aggregation and vasoconstriction and may ultimately enhance such organ injuries. The purpose of this study was to investigate the association between liver damage and 5-HT levels in the liver after intestinal I/R. The entire canine small intestine, isolated on a vascular pedicle that consisted of the proximal superior mesenteric artery and superior mesenteric vein, was subjected to 4-h ischemia by clamping these vessels and the marginal arteries supplying the proximal and distal ends of the small intestine. Hepatic blood flow, liver tissue blood flow, bile flow rate, and hepatic venous ketone body ratio (HVKBR) were measured before and at the end of intestinal ischemia and at 5, 15, and 30 min, and 1 and 2 h after reperfusion. 5-HT levels in plasma of the portal vein and hepatic vein were assayed at the same intervals. Time-matched, sham-operated animals served as controls. Intestinal I/R significantly decreased the liver tissue flow, bile flow rate, and HVKBR. Compared to those in controls, 5-HT levels in the portal vein and hepatic vein were markedly increased after reperfusion. Furthermore, intravenous administration of 5-HT receptor antagonists attenuated the liver dysfunction after intestinal reperfusion. These results suggest that intestinal I/R induces continuous disturbance of hepatic microcirculation, leading to liver dysfunction, and that 5-HT may be implicated as one of the mediators of liver dysfunction after intestinal I/R.

Effect of ursodeoxycholate in University of Wisconsin solution on long term preservation of rat livers.

To find out whether the addition of ursodeoxycholate (UDC) to University of Wisconsin (UW) solution reduces injury during preservation of the liver. Controlled laboratory study. University hospital, Germany. Preserved livers from 12 rats. Livers were flushed with 10 ml of ice-cold (0-1 degrees C) UW or iso-osmolar UW containing 5 mmol/l UDC. After preservation for 30 hours at 0-1 degrees C and 1 hour at 22 degrees C the livers were reperfused for 4 hours. Aspartate amino-transaminase, alanine aminotransferase, glutamate lactate dehydrogenase, and white blood cell (WBC) and platelet counts were measured during reperfusion. Bile flow and total bile salt secretion rate were also measured. Addition of UDC to UW reduced the release of liver enzymes, slightly increased platelet adherence, and reduced bile flow and bile salt secretion rate. The membrane-stabilising effect of UDC may explain the reduction in enzyme release. However, liver function, as expressed by bile salt secretion rate and bile flow was adversely affected.

Endotoxin-induced reduction in biliary indocyanine green excretion rate in a chronically catheterized rat model.

Using a nonstressed chronically catheterized rat model in which the common bile duct was cannulated, we studied endotoxin-induced alterations in hepatic function by measuring changes in the maximal steady-state biliary excretion rate of the anionic dye indocyanine green (ICG). Biliary excretion of ICG was calculated from direct measurements of biliary ICG concentrations and the bile flow rate during a continuous vascular infusion of ICG. Despite significant elevations in mean peak serum tumor necrosis factor-alpha (TNF-alpha) concentrations (90.9 +/- 16.2 ng/ml), there was no effect on mean rates of bile flow or biliary ICG clearance after administration of 100 microg/kg endotoxin at 6 or 24 h. Significant differences from mean baseline rates of bile flow and biliary ICG excretion did occur after administration of 1,000 microg/kg endotoxin (mean peak TNF-alpha 129.6 +/- 24.4 ng/ml). Furthermore, when rats were treated with up to 16 microg/kg of recombinant TNF-alpha, there was no change in mean rates of bile flow or ICG biliary clearance compared with baseline values. These data suggest that the complex regulation of biliary excretion is not mediated solely by TNF-alpha.

Staphylococcal enterotoxin B potentiates LPS-induced hepatic dysfunction in chronically catheterized rats.

Most models of liver dysfunction in sepsis use endotoxin (lipopolysaccharide; LPS) to induce a pathophysiological response. In our study published in this issue (Beno DWA, Uhing MR, Goto M, Chen Y, Jiyamapa-Serna VA, and Kimura RE. Am J Physiol Gastrointest Liver Physiol 280: G858-G865, 2001), the adverse effect of LPS on hepatic function in vivo was only significant at relatively high LPS doses despite high tumor necrosis factor-alpha concentrations. However, many patients with sepsis are exposed to multiple bacterial toxins that may augment the immune response, resulting in increased hepatic dysfunction. We have developed a model of polymicrobial sepsis by parentally administering a combination of staphylococcal enterotoxin B (SEB) and LPS. Using this model, we demonstrate that SEB (50 microg/kg) potentiates the effect of LPS-induced hepatic dysfunction as measured by decreased rates of biliary indocyanine green clearance and bile flow. These increases were most pronounced with doses of 10 and 100 microg/kg LPS, doses that by themselves do not induce hepatic dysfunction. This may explain the seemingly increased incidence and severity of liver dysfunction in sepsis, and it suggests that the exclusive use of LPS for replicating septic shock may not be relevant for studies of hepatic dysfunction.

Defective dietary fat processing in transgenic mice lacking aquaporin-1 water channels.

Immunocytochemistry showed expression of aquaporin-1 (AQP1) water channels at sites involved in dietary fat processing, including intrahepatic cholangiocytes, gallbladder, pancreatic microvascular endothelium, and intestinal lacteals. To determine whether AQP1 has a role in dietary fat digestion and/or absorption, mice were placed on a diet that contained 50% fat. Whereas wild-type mice (3-3.5 wk of age, 10-12 g) gained 49 +/- 5% (SE, n = 50) body weight in 8 days, and heterozygous mice gained 46 +/- 4%, AQP1 null mice gained only 4 +/- 3%; weights became similar after return to a 6% fat diet after 6 days. The null mice on a high-fat diet acquired an oily appearance, developed steatorrhea with increased stool triglyceride content, and manifested serum hypotriglyceridemia. Supplementation of the high-fat diet with pancreatic enzymes partially corrected the decreased weight gain in null mice. Absorption of [(14)C]oleic acid from small intestine was not affected by AQP1 deletion, as determined by blood radioactivity after duodenal infusion. Lipase activity in feces and small intestine was remarkably greater in AQP1 null than wild-type mice on low- and high-fat diets. Fluid collections done in older mice (that are less sensitive to a high-fat diet) by ductal cannulation showed threefold increased pancreatic fluid flow in response to secretin/cholecystokinin, but volumes, pH, and amylase activities were affected little by AQP1 deletion, nor were bile flow rates and bile salt concentrations. Together, these results establish a dietary fat misprocessing defect in AQP1 null mice.

Stimulatory influence of select spices on bile secretion in rats

Spices - cumin, coriander, ajowan, fennel, mint, and garlic, were examined for their influence on bile secretion rate and bile acid content of bile in experimental rats both as a result of continued dietary intake and single oral dose of the test spice. Groups of animals were maintained for 8 weeks on the following spice diets : Cumin (1.25 %), Coriander (2.0 %), Ajowan (0.2 %), Fennel (0.5 %), Mint (1.0 %), and Garlic (0.5%). In a separate set of rats, these test spices were also administered as a single intragastric dose (mg/kg body wt : Cumin, 600; Coriander, 400; Ajowan, 80; Fennel, 200; Mint, 400; and Garlic oil, 0.02. Bile flow rate was significantly enhanced by dietary cumin, ajowan, and garlic. Ajowan had this beneficial effect even with a single oral dose. The biliary solids were higher in the case of dietary cumin, coriander, ajowan, fennel and mint. A pronouncedly higher rate of secretion of bile acids was caused by all the test spices except garlic, compared to control, both in dietary treatment as well as in single oral dosage of the spice. Higher rate of bile acids secretion would probably contribute to the digestive stimulant action of the test spices.

Loss of serum bicarbonate after discordant liver xenotransplantation

It is a concern in liver xenotransplantation (XTx) that discordant combinations might not be sufficiently compatible for physiologic functioning in the recipient. Closer examination of the guinea pig- (GP) to-rat liver XTx model uncovered potential incompatibilities in bile production between these species. GP (along with rabbits) have the greatest bile flow rate of all species studied.1 Additionally, there is a fundamental difference between the two species in the rate of bile excretion. Bile flow in rats is bile acid dependent, whereas the rate in GP is independent of bile acid; the latter is believed to be driven osmotically by bicarbonate.2 Because bile flow is 4 times greater in GP than in rats, we tested whether the different excretion mechanisms would affect HCO3− blood levels and pH in rat recipients of GP liver xenografts (Xeno).