Inhibitory effect of selenium on biliary secretion of methyl mercury in rats

The inhibitory effect of sodium selenite on biliary secretion of methyl mercury was examined in rats. The biliary secretion of methyl mercury in rat treated with 1 mumol/kg of methyl mercury was significantly decreased by administration of selenite at doses of 0.05 mumol/kg or higher. In rats given 10 mumol/kg of methyl mercury, marked depression of biliary secretion of mercury was observed when selenite was injected at a dose of 0.2 mumol/kg. On the other hand, secretion of substantial amounts of selenium was observed when biliary secretion of mercury was depressed. When the concentration of selenium in the bile was higher than 5 nmol/ml, biliary secretion of mercury was markedly depressed independently of the dose of methyl mercury administered (1 mumol/kg or 10 mumol/kg). These results suggest that the degree of inhibitory effect of selenite may be determined by the selenium concentration in the liver or the bile after treatment with selenite rather than the molar ratio of the dose of methyl mercury and selenite. We concluded that the decrease in biliary secretion of methyl mercury induced by selenite may result from inhibition of pathway for secretion of methyl mercury from liver to bile rather than the direct formation of a complex between methyl mercury and selenium. Methyl mercury has been considered to be secreted from liver to bile as a complex with glutathione (GSH). However, administration of selenite did not affect biliary secretion of GSH or hepatic glutathione S-transferase activity. Moreover, gel filtration of liver cytosol demonstrated that the distribution pattern of hepatic methyl mercury between macromolecules and GSH was not significantly changed by administration of selenite. These results suggest that selenite does not affect complex formation of methyl mercury with GSH at least in the liver. Selenite might specifically inhibit the activity of the canalicular transporter(s) which transport complexes of methyl mercury and GSH from the liver to bile.     

Retrograde injections of formaldehyde into the biliary tree induce alterations of biliary epithelial function in rats

Formaldehyde may induce severe lesions of intrahepatic and extrahepatic bile ducts. The purpose of this study was to examine in vivo the functional consequences of an alteration of the biliary epithelium induced by a retrograde intrabiliary injection of formaldehyde in rats. After basal bile collection, a 10% formaldehyde solution was injected into the biliary tree of anesthetized rats, and the cannula was occluded for 30 minutes. Choleresis was then reestablished, and bile flow, bile acid, and bicarbonate secretion were measured both spontaneously and during ursodeoxycholate infusions. Formaldehyde injections induced a significant increase in bile flow and a marked inhibition of ursodeoxycholate-induced increase in biliary bicarbonate concentration and secretion. Biliary glucose secretion, which is normally very low, was increased about 20-fold in animals injected with formaldehyde. Histological and ultrastructural examination of the liver showed alterations of biliary epithelial cells, whereas hepatocytes, bile canaliculi, and canalicular tight junctions remained normal. Hepatocytic excretory function, as assessed by biliary secretion of bile acids, was not affected. It was concluded that short-term formaldehyde intrabiliary injections cause an inhibition of ursodeoxycholate-induced hypersecretion of bicarbonate, an increase in biliary glucose secretion, and selective structural alterations of biliary epithelial cells. These results suggest that formaldehyde retrograde biliary injection may be a useful model to study alterations of biliary epithelial function in vivo.     

Alternative reproductive strategies in the ruff, Philomachus pugnax: a mixed ESS?

BACKGROUND/AIMS: Hepatic graft dysfunction is a major management problem in the early post-liver transplantation period. Our aims were to study how liver transplantation per se affects bile formation, and to investigate the role of cyclosporine in the pathogenesis of early graft dysfunction. METHODS: Syngeneic liver transplantation used male Lewis rats. Two weeks after transplantation, the rats were randomly assigned to receive either daily subcutaneous injections of cyclosporine 10 mg/kg for 1 week (n=8), or daily saline injections (Placebo, n=8). 24-h bile collections were performed 18 h after the last injection. Eight non-transplanted rats served as controls. RESULTS: Liver transplantation per se (Placebo) significantly increased basal bile flow (51%), particularly that portion which was bile salt-independent flow (81%), but did not impair bile salt kinetics or biliary lipid composition. Cyclosporine reduced basal bile flow and bile salt-independent flow by 41% and 30%, respectively. Bile salt synthesis was 52% suppressed, leading to a 22% decrease in the bile salt pool size. The recycling frequency of the bile salt pool was unaffected. The drug inhibited bile salt (37%) and phospholipid (23%) outputs; cholesterol secretion remained unaltered. This significantly elevated the cholesterol saturation of bile (25%). CONCLUSIONS: Liver transplantation per se is choleretic and does not impair bile formation or lipid composition in this inbred rat model. Parenteral administration of high-dose cyclosporine induces cholestasis by inhibiting bile salt secretion and BSIF. Bile salt synthesis is down-regulated and the bile salt pool size decreased. The drug adversely affects biliary lipid composition by differential inhibition of bile salt and phospholipid outputs relative to an unchanged cholesterol secretion.     

Expression of the transcriptional regulator Egr-1 in experimental glomerulonephritis: requirement for mesangial cell proliferation

BACKGROUND/AIMS: The hepatic transport of bile salts can be regulated by changes in bile salt pool size and/or in the flux of bile salts through the liver. Prolonged bile salt pool depletion is associated with down-regulation of maximum taurocholate transport and decreased canalicular membrane specific bile salt binding sites. This study was undertaken to investigate: a) whether adaptive down-regulation of maximum hepatic bile salt transport occurs to the same extent for bile acids of different hydrophobicity; and b) the role of microtubule-dependent vesicular pathway in the adaptive changes of bile salt transport capacity. METHODS: Male rats were subjected to 24-h or 48-h external biliary diversion to induce bile salt pool depletion. Basal bile flow, bile salt secretion and lipid secretion, maximum secretory rate of three bile salts of different hydrophobicity (tauroursodeoxycholate, taurocholate and taurochenodeoxycholate) and changes in the biliary excretion of two markers of the microtubule-dependent vesicular pathway (horseradish peroxidase and polyethyleneglycol molecular weight-900) were measured in control and bile salt-depleted rats. Taurocholate-stimulated horseradish peroxidase biliary excretion was also assessed in order to define whether the restoration of bile salt flux across the hepatocytes increased the excretion of this marker in bile salt-depleted rats. RESULTS: The reduction in the maximum secretory rate of the three bile salts under study observed after prolonged biliary diversion was clearly related to their hydrophobicity, with greater reduction for taurochenodeoxycholate and smaller reduction for tauroursodeoxycholate, compared with taurocholate. The biliary excretion of vesicular transport markers was significantly reduced in bile salt-depleted rats. However, when stimulated by taurocholate, biliary excretion of horseradish peroxidase was similar to controls. CONCLUSIONS: The magnitude of the decrease of the hepatic bile salt maximum transport capacity seen after bile salt pool depletion is directly related to the hydrophobicity of the bile salt infused. A functionally depressed vesicular transport pathway appears to be also a contributing factor to this phenomenon.     

Thyroid hormone is required for dietary fish oil to induce hypersecretion of biliary cholesterol in the rat

In the rat, both fish oil diet and thyroid hormone replacement are reported to augment bile cholesterol secretion out of proportion to bile flow or secretion of other bile lipids. We sought common mechanisms for these effects and evaluated the role of phospholipid fatty acid composition in the process. Methimazole-treated hypothyroid rats were fed low-fat chow or chow supplemented with 10% corn oil or fish oil, and were studied before and after thyroid hormone treatment. Serum, hepatic, and bile lipids were measured, phospholipid fatty acid composition determined, and hepatic 3-hydroxy-3-methylglutaryl CoA reductase activity assayed. Fish oil diet stimulated cholesterol secretion into bile only after thyroid hormone was given, and this action was synergistic with that of thyroid hormone. Reduced serum cholesterol in fish oil-treated rats was associated with increased biliary cholesterol secretion and diminished hepatic cholesterol content. This suggests that augmented biliary cholesterol secretion may contribute to the fish oil-induced reduction of serum cholesterol. No definite relationship between hepatic or biliary phospholipid fatty acid composition and biliary secretion was apparent, although high bile cholesterol secretion was associated with a low percentage of hepatic and bile phospholipid linoleic acid.     

Diet, overfeeding, and moderate dietary restriction in control Sprague-Dawley rats: II. Effects on age-related proliferative and degenerative lesions

This study compared the effects of ad libitum (AL) overfeeding and moderate dietary restriction (DR) of 2 different diets on Sprague-Dawley (SD) rat survival and spontaneous, age-related proliferative and degenerative lesions. SD rats were fed Purina Rodent Chow 5002 or a modified Rodent Chow 5002-9 containing lower protein, fat, metabolizable energy, and increased fiber by AL or by DR at 65% of the AL amount by measurement or time (6.5 hr). At 106 wk, rats fed the 5002-9 diet AL did not have significantly improved survival over rats fed the 5002 diet AL. The 5002 diet fed DR by time (6.5 hr) improved survival for males but not females. Only DR by measurement of both diets resulted in lower mortality for both sexes. By 106 wk rats fed either diet by AL had the same brain weights as DR fed rats, but AL fed rats had greater body weight, body fat content, and increased heart, lung, kidney, liver, adrenal, thyroid, and pituitary weights that correlated with an increased incidence and severity of degenerative and/or proliferative lesions in these organs. Moderate DR delayed the progression of chronic nephropathy by delaying the early development of glomerular hypertrophy that initiates the development of glomerular sclerosis and nephron loss in AL overfed rats. Moderate DR lowered the incidence, severity, and progression of cardiomyopathy and other degenerative, age-related lesions and appeared to delay the development of reproductive senescence in SD females. The conclusion from this study is that moderate DR delayed onset and progression of degenerative lesions, and death due to cardiovascular or renal disease, and thus potentially improves the bioassay to detect compound-specific chronic toxicity.     

Mechanism of biliary lipid secretion in the rat: a role for bile acid-independent bile flow?

Bile acid-induced lipid secretion was compared in unanesthetized normal control and Groningen Yellow Wistar rats during variations in endogenous bile acid output. Groningen Yellow rats express a genetic defect in the biliary secretion of various organic anions. During a 5-hr period after interruption of the enterohepatic circulation, bile acid secretion decreased from 36.4 +/- 1.8 to 1.9 +/- 0.3 mumol per 30 min in normal control rats and from 37.1 +/- 2.8 to 1.8 +/- 0.2 mumol per 30 min in Groningen Yellow rats, respectively (mean +/- S.E.M., n = 5). The relationship between bile acid secretion and bile flow showed similar slopes (normal control, 8.74 +/- 0.44 microliter/mumol and Groningen Yellow rats, 7.71 +/- 0.42 microliter/mumol) but different y-intercepts (normal control, 243 +/- 8 and Groningen Yellow, 127 +/- 4 microliters per 30 min; p < 0.001), corresponding to a 47% reduction of the bile acid-independent fraction of bile flow in Groningen Yellow rats. During the course of the experiment, the ratio of lipids (phospholipids plus cholesterol) to bile acids increased in both strains more than threefold but was permanently higher in Groningen Yellow than in normal control rats (p = 0.035), implying that Groningen Yellow rats continuously secreted more lipid per bile acid. No differences in bile acid pool composition or in bile canalicular membrane composition and fluidity between the two strains were detected. The results indicate that apart from previously demonstrated factors (bile acid concentration, bile acid composition and hydrophilic organic anion concentration in bile), another parameter affects the efficacy of bile acids to induce biliary lipid secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ethynylestradiol on biliary excretion of bile acids, phosphatidylcolines, and cholesterol in the bile fistula rat

The effects of ethynylestradiol on endogenous bile acids, their capacity to conjugate and excrete intravenously infused cholic acid, the concentrations of biliary cholesterol and lecithin, and the individual molecular species of phosphatidylcholine have been determined in male and female Sprague-Dawley rats. Endogenous biliary bile acids were analyzed by gas-liquid chromatography-mass spectrometry. Eleven bile acids were identified and several minor bile acids, primarily muricholates, could not be completely characterized. After 5 days of treatment with ethynylestradiol (1 mg/kg per day), the percentage of cholic acid decreased and the percentage of 6beta-hydroxylated bile acids, including several monounsaturated species, increased. Ethynylestradiol caused a decrease in bile acid-independent bile flow. Intravenous infusion of cholic acid at a high concentration caused cholestasis in control animals but, after ethynylestradiol treatment, cholestasis developed during the infusion of a much lower concentration of cholate, indicating a lowered threshhold for bile acid-induced cholestasis. In the treated rats, there was a slight increase in excretion of unconjugated endogenous bile acids, and a striking impairment of conjugation of intravenously administered cholic acid. One of the few sex-related differences observed was an increased concentration of biliary phospholipids in untreated male rats. Both phospholipid and cholesterol concentrations in the bile were higher in the treated animals. The molar percentage of cholesterol was always 1-2%, but it was slightly higher in treated animals, especially males. Ethynylestradiol treatment also affected biliary phospholipid by causing a marked increase of phosphatidylcholine species containing palmitic and oleic acid residues and a decrease of species containing stearic and linoleic acid residues. There was no increase in biliary excretion of long chain polyunsaturated species, which might have indicated damage to membranes, in response to ethynylestradiol either alone or with cholic acid infusion. Some of these ethynylestradiol-induced changes in biliary bile acid and lipid excretion are probably peculiar to the rat, but others, such as the increase in molar percentage of cholesterol and cholestasis, may be relevant to disorders in man, especially cholesterol gallstones and idiopathic cholestasis of pregnancy.     

Breath ethane as a marker of reactive oxygen species during manipulation of diet and oxygen tension in rats

Breath ethane, O2 consumption, and CO2 production were analyzed in 24-mo-old female Fischer 344 rats that had been fed continuously ad libitum (AL) or restricted 30% of AL level (DR) diets since 6 wk of age. Rats were placed in a glass chamber that was first flushed with air, then with a gas mixture containing 12% O2. After equilibration, a sample of the outflow was collected in gas sampling bags for subsequent analyses of ethane and CO2. The O2 and CO2 levels were also directly monitored in the outflow of the chamber. O2 consumption and CO2 production increased for DR rats. Hypoxia decreased O2 consumption and CO2 production for the AL-fed and DR rats. These changes reflect changes in metabolic rate due to diet and PO2. A significant decrease in ethane generation was found in DR rats compared with AL-fed rats. Under normoxic conditions, breath ethane decreased from 2.20 to 1.61 pmol ethane/ml CO2. During hypoxia the levels of ethane generation increased, resulting in a DR-associated decrease in ethane from 2.60 to 1.90 pmol ethane/ml CO2. These results support the hypothesis that DR reduces the level of oxidative stress.     

The effects of diet, ad libitum overfeeding, and moderate dietary restriction on the rodent bioassay: the uncontrolled variable in safety assessment

Ad libitum (AL) overfeeding is the most significant, uncontrolled variable affecting the outcome of the current rodent bioassay. There is a highly significant correlation between AL food consumption, the resultant obesity and body weight, and low 2-yr survival in rodents. AL feeding of diets with lowered protein, metabolizable energy (ME), and increased fiber does not improve survival. Only dietary restriction (DR) of all diets tested significantly improves survival and delays the onset of spontaneous degenerative disease (i.e., nephropathy and cardiomyopathy) and diet-related tumors. Moderate DR results in an incidence of spontaneous tumors similar to AL-fed rats, but the tumors are found incidentally and do not cause early mortality. There is a decreased age-adjusted incidence of pituitary and mammary gland tumors in moderate DR-fed rats, but tumor growth time is similar between AL and DR rats with only a delay in tumor onset time seen in DR-fed groups. Moderate DR does not significantly alter drug-metabolizing enzyme activities nor the toxicologic response to 5 pharmaceuticals tested at maximum tolerated doses (MTDs). However, moderate DR-fed rats did require much higher doses of 4 additional pharmaceutical compounds before classical MTDs were produced. Toxicokinetic studies of 2 of these compounds demonstrated equal or higher steady-state systemic exposures to parent drug and metabolites in moderate DR-fed rats. Markers of oxidative stress (lipid peroxidation, protein oxidation) are decreased and cytoprotective anti-oxidant markers are preserved in moderate DR-fed rats. But moderate DR does not delay reproductive senescence in female rats. Only marked DR delays reproductive senescence compared to AL and moderate DR-fed female rats. These and other data indicate that moderate DR is the most appropriate method of dietary control for the rodent bioassay when used to assess pharmaceuticals for human safety and compounds for risk assessment.     

The effects of castration and treatment with testosterone on the biliary excretion of (3H)aldosterone in rats

The rate of excretion of aldosterone radiometabolites into the bile duct cannulation, and the intravenous injection of (3H)aldosterone, was demonstrated to be markedly increased in male rats following castration. In 1 h, 72% of the injected 3H-radioactivity was excreted in the bile of castrated male rats compared with 26% in the intact male control rats. Castration of the males led to the increased biliary excretion of aldosterone metabolites and the elimination of the sex-dependence of this process in rats. The ovariectomy of female rats did not substantially increase the rate of excretion of aldosterone metabolites via the bile. Castrated male rats treated with testosterone excreted aldosterone metabolites into the bile at a slower rate. A similar treatment of ovariectomized female rats with testosterone also significantly slowed the rate of biliary excretion of the aldosterone metabolites. These findings suggest that the presence of androgens plays an important role in regulating the routes of hepatic metabolism of aldosterone and the rates of clearance of aldosterone and its metabolites from the plasma into the bile of rats.     

Modulation of methylnitrosourea-induced breast cancer in Sprague Dawley rats by dehydroepiandrosterone: dose-dependent inhibition, effects of limited exposure, effects on peroxisomal enzymes, and lack of effects on levels of Ha-Ras mutations

Although bile salts play an important role in the secretion of biliary lipid, little is known about the relationship between bile salt hydrophobicity and the selection of lecithin species to be secreted into bile. We therefore investigated whether bile salts modulate the selection of biliary lecithin subspecies. Rats that were depleted of the bile salt pool were infused with taurocholate (50, 100, 200, and 400 nmol/min/100 g body weight), taurochenodeoxycholate (25, 50, 100, and 200 nmol/min/100 g body weight), tauroursodeoxycholate (100, 200, 400, and 800 nmol/min/100 g body weight), or taurobetamuricholate (100, 200, 400, and 800 nmol/min/100 g body weight). Bile was collected to analyze bile flow, bile acid output, cholesterol levels, and lecithin levels. The hydrophobic-hydrophilic balance of the bile salts and biliary lecithin species was assessed by determining the retention times during reverse-phase high-performance liquid chromatography. Biliary lecithin secretion rates correlated with the hydrophobicity index of the biliary bile salts administered. Thus, biliary lecithin hydrophobicity increased with increasing bile salt hydrophobicity, whereas the molar cholesterol-lecithin ratio in the bile decreased. In conclusion, bile salt hydrophobicity regulates the selection of biliary lecithin subspecies during biliary secretion and thereby modulates, at least in part, bile cholesterol metastability. Thus, bile salt hydrophobicity accounts for the physicochemical conditions determining bile lipid metastability.     

A simple method for bile duct anastomosis and interval bile collection in the liver-transplanted rat

A mini T-tube is introduced for the bile duct anastomosis of rat liver transplantation as well as interval bile collection. The validity of the T-tube was evaluated in 14 liver-transplanted rats and compared to 14 rats using traditional stent for bile duct anastomosis. Changes of biliary tree after the T-tube anastomosis were examined by T-tube cholangiography on sample rats at 4 days and at 4 months after liver grafting. Additionally, bile volumes and rates of bile salt secretion were compared in the continuously flowing cannula and the chronic T-tube fistula in normal rats. The results show that the mini T-tube facilitates bile duct anastomosis and study of bile secretion after liver transplantation in rats without increase in surgical difficulty or interference of biliary enterohepatic circulation.     

Effect of a bacterial lipopolysaccharide on biliary excretion of a beta-lactam antibiotic, cefoperazone, in rats

Klebsiella pneumoniae O3 lipopolysaccharide (LPS) has been found to dramatically modify the pharmacokinetics of the beta-lactam antibiotic cefazolin in rats. This study investigated the effect of LPS on the biliary excretion of the beta-lactam antibiotic cefoperazone (CPZ) in rats. CPZ is known to be actively secreted into the bile by a carrier-mediated transport system. LPS (250 micrograms/kg of body weight) was infused for 20 to 30 min 2 h before an intravenous administration of CPZ (20 mg/kg). The pharmacokinetic parameters of CPZ were estimated by a noncompartment model. LPS induced a significant decrease in the systemic clearance (by approximately 50%) and an increase in the mean residence time of CPZ. Significant decreases were also seen in the bile flow rate and in the biliary recovery of unchanged CPZ in the LPS-treated rats. LPS tended to increase the proportion of urinary excretion of CPZ. LPS significantly decreased the biliary clearance (by approximately 55%) and renal clearance (by approximately 35%) of CPZ. However, no changes in the volume of distribution at steady state for CPZ were observed between the treatment groups. Our findings suggest that LPS induces changes in the pharmacokinetics of CPZ as a result of changes occurring in the biliary secretory system.     

Preliminary study of tolerance of ambiguity of individuals reporting paranormal experiences

Bromosulfophthalein and papaverine have been demonstrated to inhibit biliary lipid secretion without affecting secretion of bile salts in normal rats, so-called uncoupling. Bromosulfophthalein inhibits the capacity of intracanalicular bile salt micelles to induce biliary lipid secretion, and papaverine inhibits vesicular transport within the hepatocyte. We compared the effects of bromosulfophthalein and papaverine on biliary lipid secretion in normal Sprague-Dawley rats and Eizai hyperbilirubinuria rats. The fatty acyl chain saturation in biliary lecithin increased during bromosulfophthalein infusion and decreased during papaverine infusion in Sprague-Dawley rats. Bromosulfophthalein had no effect on biliary lipid secretion in Eizai rats, while papaverine induced uncoupling. The degree of fatty acyl chain saturation in biliary lecithin was unchanged during bromosulfophthalein infusion, but decreased with papaverine in Eizai rats. We deduce that selection of biliary lecithin species occurs at various points in the lipid transport pathway at intracellular and intracanalicular sites.     

Effect of P-450 inducers on biliary excretion of glutathione and its hydrolysis products. Correlation between hepatic gamma-glutamyltranspeptidase activity and the proportion of glutathione hydrolysis products in bile

This study was designed to determine if a relationship exists between hepatic gamma-glutamyltranspeptidase (gamma-GT) activity and the biliary excretion of glutathione (GSH) and its hydrolysis products. Rats were pretreated with the following microsomal enzyme inducers: pregnenolone-16 alpha-carbonitrile (PCN), dexamethasone (DEX), 3-methylcholanthrene, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), phenobarbital (PB), ethanol (ETOH), trans-stilbene oxide (TSO), butylated hydroxyanisole (BHA), isosafrole (ISF), clofibrate, and benzo(a)pyrene. Hepatic gamma-GT activity was quantitated spectrophotometrically; bile and liver samples were analyzed by HPLC for reduced and oxidized GSH and their hydrolysis products (cysteine, cysteinylglycine, and cysteinylglycine disulfide). Administration of the inducers had only minor effects on hepatic GSH concentration, as BHA was the only agent to increase GSH concentration. However, these inducers had a pronounced effect on the biliary excretion of total thiol-derived sulfur as PCN, PB, and ISF produced an increase, whereas TCDD, ETOH, and TSO caused a decrease. The relative amount of the GSH hydrolysis products in bile was highly dependent on gamma-GT activity. For example, hepatic gamma-GT activity was increased by PCN, DEX, BHA, TSO, and ISF. They also increased the GSH hydrolysis products to total thiol-derived sulfur ratio in bile. In conclusion, the ratio of GSH hydrolysis products to total thiol-derived sulfur excreted in rat bile reflects the hepatic gamma-GT activity.     

Role of glutathione in hepatic bile formation during reperfusion after cold ischemia of the rat liver

BACKGROUND/AIMS: Liver reperfusion following cold ischemia is frequently associated with diminished bile flow in patients undergoing liver transplantation. Glutathione is a major determinant of bile-acid independent bile flow, and the effects of cold ischemia on biliary glutathione excretion are unknown. METHODS: We examined the effects of cold ischemia (University of Wisconsin solution (4 degrees C), 24 h) with subsequent reperfusion (100 min) on biliary glutathione excretion in a recirculating system. Since glutathione might represent an important antioxidant within the biliary tract and oxidative stress in the biliary tract during reperfusion could contribute to the pathogenesis of bile duct injury after liver transplantation, we also assessed bile duct morphology in reperfused livers of mutant TR- -rats, in whom biliary excretion of glutathione is already impaired. RESULTS: Hepatic bile formation was diminished in reperfused Wistar rat livers after cold ischemia. Biliary glutathione concentrations and output were significantly decreased and correlated with postischemic changes in bile secretion. An increased biliary oxidized glutathione/glutathione ratio, indicating oxidative stress, was detected only immediately after the onset of reperfusion. Basal bile flow rates in TR- -rat livers which were already markedly reduced in control-perfused livers, decreased further during the early but not the later reperfusion period. Reperfusion of both Wistar and TR- -rat livers was not associated with electron microscopic evidence of bile duct damage. CONCLUSIONS: We conclude that impaired biliary excretion of glutathione contributes to decreased bile flow after cold ischemia. The absence of biliary glutathione does not appear to promote ultrastructural evidence of bile duct injury during reperfusion in the isolated perfused rat liver.     

Granulocyte colony-stimulating factor enhances endotoxin-induced decrease in biliary excretion of the antibiotic cefoperazone in rats

We have recently reported that endotoxin (lipopolysaccharide [LPS]) derived from Klebsiella pneumoniae dramatically decreased the biliary excretion of the beta-lactam antibiotic cefoperazone (CPZ), which is primarily excreted into the bile via the anion transport system, in rats. The present study was designed to investigate the effect of human recombinant granulocyte colony-stimulating factor (G-CSF), which is reported to be beneficial in experimental models of inflammation, on the pharmacokinetics and biliary excretion of CPZ in rats. CPZ (20 mg/kg of body weight) was administered intravenously 2 h after the intravenous injection of LPS (250 microgram/kg). G-CSF was injected subcutaneously at 12 microgram/kg for 3 days and was administered intravenously at a final dose of 50 microgram/kg 1 h before LPS injection. Peripheral blood cell numbers were also measured. LPS dramatically decreased the systemic and biliary clearances of CPZ and the bile flow rate. Pretreatment with G-CSF enhanced these decreases induced by LPS. The total leukocyte numbers were increased in rats pretreated with G-CSF compared to the numbers in the controls, while the total leukocyte numbers were decreased (about 3,000 cells/microliter) by treatment with LPS. Pretreatment with G-CSF produces a deleterious effect against the LPS-induced decrease in biliary secretion of CPZ, and leukocytes play an important role in that mechanism.     

T-kininogen is a biomarker of senescence in rats

We have previously reported on the identification of T-kininogen (T-KG) as a gene whose expression is increased during senescence in male Sprague-Dawley (S-D) rats. Serum T-KG levels increase 2.5-4 months before the time of death for any given animal, irrespective of the actual age of the animal at the time of this event. Furthermore, dietary restriction (DR) delays, but does not prevent, the increase in serum T-KG levels. In the present study, we have assessed whether or not the age-related increase in T-KG is a common feature of senescence in other strains of rat. We have analyzed hepatic T-KG mRNA levels in male Fischer 344 rats (F344), as well as in male and female (Fischer 344 x Brown Norway)F1 rats (F1). In both of these strains, we observed a dramatic increase in hepatic T-KG mRNA levels when male rats approach senescence. The mRNA levels behave similarly in F1 and S-D rats, in that the increase occurs late in life, and it is either repressed or delayed by DR. In contrast, the increase in T-KG mRNA levels in F344 rats occurs earlier in life, and is not significantly affected by DR. Young female F1 rats fed ad libitum (AL) show a statistically significant (P = 0.0009) 2.6-fold higher level of T-KG mRNA, as compared to their male counterparts. Thus, while we still observe an age-related increase in this parameter in both AL and DR female F1 rats, the difference is statistically significant (P = 0.0001) only in DR animals. We conclude that the increase in T-KG gene expression is a common feature of senescence and that, at least in males of these commonly used rat strains, T-KG can be used as a reliable biomarker of aging. Since the increase in T-KG gene expression does not appear to correlate with inflammatory processes, and since different strains of animals succumb to different pathologies, these results further suggest that the increase in T-KG expression might be related to the process of aging per se, rather than to any given age-related pathology.