Hepatobiliary disposition of rhodamine 123 in isolated perfused rat livers

The disposition of rhodamine 123 (RH-123), a known marker of P-glycoprotein, and its liver-generated glucuronide metabolite (RH-Glu), a marker of Mrp2, was studied in an isolated perfused rat liver model. Livers were perfused with a buffer containing 0.1 microg ml(-1) RH-123 for 30 or 60 min or for 30 min followed by 90 min of drug-free perfusion, and the concentrations of the drug and its metabolites were determined in the perfusate, bile, and the liver tissue. The outlet perfusate concentrations of RH-123 and RH-Glu reached an apparent plateau during the continuous infusion of the drug, with a very extensive extraction ratio of approximately 96% for the parent drug. However, the biliary excretion rates of both RH-123 and generated RH-Glu continued to rise almost linearly during the entire 60 min of drug infusion. This was associated with a linear increase in the amount of RH-123 recovered in the liver between 30 and 60 min of drug infusion, resulting in a significant (>50% of the administered dose) recovery of the marker in the liver both after 30 and 60 min of perfusion. Additionally, the washout experiments showed that the declines in the biliary excretion rates of RH-123 and RH-Glu were parallel to that of RH-123 concentration in the liver in the absence of drug input. The hepatobiliary disposition of RH-123 in rats is unique because of its substantial and time-dependent accumulation in the liver, resulting in a lack of steady-state in its biliary excretion despite apparent steady-state in the perfusate.     

Alteration of fexofenadine disposition in the rat isolated perfused liver following injection of bacterial lipopolysaccharide

1. The aim of the present study was to examine the effect of bacterial lipopolysaccharide (LPS) on the disposition of an organic anion transporting polypeptide and P-glycoprotein substrate in the rat isolated perfused liver. 2. Male Sprague-Dawley rats were divided into four groups. Three of the groups received 1, 2.5 or 5 mg/kg, i.p., Escherichia coli LPS in sterile saline. The fourth group received an equivalent volume of sterile saline i.p. Twenty-four hours after treatment, rats were anaesthetized and the liver isolated and perfused with fexofenadine at an initial concentration of 2000 ng/mL in a recirculating system. Perfusate and bile samples were collected for 60 min and the liver was collected at the end of the perfusion. Fexofenadine concentrations were determined by HPLC. Fexofenadine pharmacokinetic parameters, the final liver : perfusate (L : P) and bile : liver (B : L) concentration ratios were determined. 3. Injection of LPS changed the hepatic disposition of fexofenadine. The changes were most marked in the 5 mg/kg LPS group. Notably, clearance from the perfusate (CL) and into the bile (CLB; 5.9 +/- 0.6 and 1.24 +/- 0.20 mL/min, respectively), L : P (44 +/- 11) and B : L (17 +/- 2) were all reduced (P < 0.05) in this group compared with control (CL 10.0 +/- 1.1 mL/min; CLB 2.7 +/- 0.5 mL/min; L : P 87 +/- 14; and B : L 30 +/- 4). 4. In conclusion CL and CLB were reduced following treatment with LPS in a manner consistent with downregulation of both canalicular and sinusoidal transport.     

Effects of hypoxia/reperfusion injury on drug disposition in the rat isolated perfused liver

1. Ischaemia-reperfusion injury is known to be associated with a range of functional and structural alterations in the liver. However, the effect of this injury on drug disposition is not well understood. The present study was designed to examine the effects of hypoxia/reperfusion on the disposition of glutamate and propranolol in the rat isolated perfused liver. Both glutamate and propranolol are mainly metabolised in the pericentral region of the liver. 2. Hypoxia/reperfusion was established using the slow flow-reflow method of perfusion in both anterograde and retrograde perfusion. Glutamate metabolism was measured by the recovery of [(14)C]-glutamic acid and [(14)C]-labelled metabolites in a single pass in both anterograde and retrograde perfusion in the presence of a steady state concentration of unlabelled glutamic acid. Propranolol disposition, mean transit time and normalized variance were assessed from the outflow concentration-time profile of unchanged [(3)H]-propranolol determined after a bolus injection of [(3)H]-propranolol using HPLC and liquid scintillation counting. 3. Hypoxia/reperfusion of livers did not affect oxygen consumption, but caused significant changes in enzyme release, lignocaine hepatic availability and bile flow. 4. Hypoxia/reperfusion did not affect the hepatic metabolism of glutamate to carbon dioxide or the hepatic extraction of propranolol. Small but significant changes were evident in the distribution parameters of mean transit time and vascular disposition for the hypoxic-ischaemic liver. 5. It is concluded that reperfusion injury induced by slow flow-reflow perfusion did not influence the extraction of glutamate or propranolol, but may have affected pericentral morphology and solute distribution.     

Disposition of quinapril and quinaprilat in the isolated perfused rat kidney

An isolated perfused rat kidney model was used to probe the renal disposition of quinapril and quinaprilat after separate administration of each drug species. Control studies were performed with drug-free perfusate (n=8) and perfusate containing quinapril (n=9) quinaprilat (n=7) at initial drug concentrations of 1000 ng/ml (including corresponding tracer levels of tritiated drug). Physiologic parameters were within the normal range of values for this technique and were stable for the duration of each experiment. Quinapril and quinaprilat concentrations were determined in perfusate, urine, and perfusate ultrafiltrate using a specific and sensitive reversed-phase HPLC procedure with radiochemical detection, coupled to liquid scintillation spectrometry. Perfusate protein binding was determined using an ultrafiltration method at 37°C. The total renal learance of quinapril (CLr) was calculated asDose/AUC (0-∞), and is represented by the sum of its urinary and metabolic clearances. The urinary clearances (CLe) of quinapril and quinaprilat were calculated as urinary excretion rate divided by midpoint perfusate concentration for each respective species. Of the total renal clearance for quinapril (CLr=4.49 ml/min), less than 0.1% was cleared as unchanged drug (CLe=0.004 ml/min); over 99% of the drug was cleared as quinaprilat formed in the kidney. The clearance ratio of quinapril [CR=CLr/(fu·GFR)] was 41.0, a value representing extensive tubular secretion into the renal cells. Following quinaprilat administration, the clearance ratio of metabolite [CR=CLe/(fu β GFR)] was 3.85, indicating a net secretion process for renal elimination. This work was supported in part by a gift from Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company and by Grant R01 GM35498 from the National Institutes of Health.     

Transformation and action of extracellular NAD+ in perfused rat and mouse livers

Aim:

Transformation and possible metabolic effects of extracellular NAD⁺ were investigated in the livers of mice (Mus musculus; Swiss strain) and rats (Rattus novergicus; Holtzman and Wistar strains).

Methods:

The livers were perfused in an open system using oxygen-saturated Krebs/Henseleit-bicarbonate buffer (pH 7.4) as the perfusion fluid. The transformation of NAD⁺ was monitored using high-performance liquid chromatography.

Results:

In the mouse liver, the single-pass metabolism of 100 μmol/L NAD⁺ was almost complete; ADP-ribose and nicotinamide were the main products in the outflowing perfusate. In the livers of both Holtzman and Wistar rats, the main transformation products were ADP-ribose, uric acid and nicotinamide; significant amounts of inosine and AMP were also identified. On a weight basis, the transformation of NAD⁺ was more efficient in the mouse liver. In the rat liver, 100 μmol/L NAD⁺ transiently inhibited gluconeogenesis and oxygen uptake. Inhibition was followed by a transient stimulation. Inhibition was more pronounced in the Wistar strain and stimulation was more pronounced in the Holtzman strain. In the mouse liver, no clear effects on gluconeogenesis and oxygen uptake were found even at 500 μmol/L NAD⁺.

Conclusion:

It can be concluded that the functions of extracellular NAD⁺ are species-dependent and that observations in one species are strictly valid for that species. Interspecies extrapolations should thus be made very carefully. Actually, even variants of the same species can demonstrate considerably different responses.     

Effect of cadmium on bromosulfophthalein kinetics in the isolated perfused rat liver system.

Bromosulfophthalein (BSP) is a relatively nontoxic organic anion used as an in vivo indicator of liver performance. Elimination of BSP via the biliary system following iv injection requires dissociation from albumin in plasma, translocation across the sinusoidal membrane, conjugation with glutathione within the hepatocyte, translocation across the bile canalicular membrane, and excretion in bile. The effects of cadmium (Cd), anin vivo hepatotoxicant in rats, on BSP kinetics in the isolated perfused rat liver (IPRL) were studied to investigate the interaction between liver toxicity and BSP kinetics. Livers were isolated from male Fisher 344 rats. After a 30-min period for acclimation to the IPRL system, livers were dosed with Cd (as cadmium acetate), in the presence of 0.25% bovine serum albumin, to give initial concentrations of 10 and 100 microM. Sixty min after Cd dosing, the IPRL system was dosed with BSP to give an initial concentration of 150 microM and the elimination kinetics of BSP from the perfusion medium were monitored. Cadmium concentrations in livers at the end of the experiments were 60 +/- 4 and 680 +/- 210 micro mol/kg for the 10 and 100 microM doses, respectively. Exposure to 10 microM Cd for 60 min resulted in a reduction in bile flow, no significant effect on lactate dehydrogenase (LDH) leakage, and slight effects on BSP clearance. Similar studies following exposure to 100 microM Cd showed a dramatic decrease in bile flow with complete cholestasis 60 min after Cd addition. LDH leakage into perfusion medium at the end of the experiment was less than 10%, indicating that Cd affected bile production well before the liver showed significant signs of necrosis. Clearance of BSP from the perfusion medium was dramatically reduced. Taken together, the data indicate that Cd has a significant effect on the kinetics of BSP in the IPRL and the dominant effects were mediated through the cholestatic effect of Cd.     

N(G)-nitro-L-arginine methyl ester potentiates anaphylactic venoconstriction in rat perfused livers

1. The effects of the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) on anaphylaxis-induced venoconstriction were examined in rat isolated livers perfused with blood-free solutions in order to clarify the role of NO in anaphylactic venoconstriction. 2. Rats were sensitized with ovalbumin (1 mg) and, 2 weeks later, livers were excised and perfused portally in a recirculating manner at a constant flow with Krebs'-Henseleit solution. The antigen (ovalbumin; 0.1 mg) was injected into the reservoir 10 min after pretreatment with L-NAME (100 micromol/L) or D-NAME (100 micromol/L) and changes in portal vein pressure (Ppv), hepatic vein pressure (Phv) and perfusate flow were monitored. In addition, concentrations of the stable metabolites of NO ( and ) were determined in the perfusate using an HPLC-Griess system. 3. The antigen caused hepatic venoconstriction, as evidenced by an increase in Ppv from a mean (SEM) baseline value of 7.7 +/- 0.1 cmH2O to a peak of 21.4 +/- 1.1 cmH2O at 3 min in D-NAME-pretreated livers. Pretreatment with L-NAME augmented anaphylactic venoconstriction, as reflected by a higher Ppv (27.4 +/- 0.8 cmH2O) after antigen than observed following D-NAME pretreatment. The addition of L-arginine, a precursor for the synthesis of NO, reversed the augmentation of anaphylactic venoconstricion by L-NAME. This suggests that hepatic anaphylaxis increased the production of NO, which consequently attenuated anaphylactic venoconstriction. However, perfusate NOx levels did not increase significantly after antigen in livers pretreated with either L-NAME or D-NAME. 4. In conclusion, L-NAME potentiates rat anaphylactic hepatic venoconstriction, suggesting that NO contributes to the attenuation of the venoconstriction. However, this functional evidence was not accompanied by corresponding changes in perfusate NOx concentrations.     

Simulation of trichloroacetic acid kinetics in the isolated perfused rat liver using a biologically based kinetic model.

Trichloroacetic acid (TCA) is a contaminant of drinking water. It induces peroxisome proliferation in livers of rats and mice and is hepatocarcinogenic in the latter species. Previous experimental studies of the kinetics of TCA in the isolated perfused rat liver (IPRL) at two doses have been reported. To gain more insight into the mechanistic processes controlling TCA kinetics in the liver a biologically based kinetic (BBK) model for the IPRL was used to analyze the experimental data. The IPRL was exposed to 25, 250, or 1000 microM TCA for 2 h in a recirculating perfusion system. These doses were not cytotoxic. The BBK model simulated the TCA concentration in perfusion medium and liver, and the biliary excretion of TCA. Separate protein binding studies showed that over 90% of TCA was bound to albumin in the perfusion medium whereas binding in liver homogenate was much lower. Integrating the information on protein binding into the BBK model, the hepatic uptake of TCA and its biliary excretion could be fitted assuming asymmetrical saturable transport at the sinusoidal membrane and linear transport at the bile canalicular membrane. To validate the BBK model, additional washout experiments were conducted in which the perfusion medium was replaced with TCA-free medium after 30 min of exposure of the liver to 1000 microM TCA. This approach illustrates the usefulness of BBK modeling for analyzing experimental kinetic data and gaining insight in kinetic mechanisms controlling the behavior of a chemical in the liver.     

离体大鼠肾脏灌流技术在发现和评价促尿酸排泄药物中的初步应用

目的为建立发现和评价促尿酸排泄药物作用的离体模型,采用离体大鼠肾脏灌流技术,观察尿酸在离体肾脏中排泄特点和丙磺舒对尿酸排泄影响。方法制备离体大鼠肾脏灌流模型,随机分为对照组和丙磺舒处理组,以含复方氨基酸和65g.L-1牛血清白蛋白的K-H灌流液循环灌流90min,定时收集导尿管流出液和灌流液,测定其中菊粉、钠、葡萄糖及尿酸含量,计算肾功能参数和尿酸排泄情况。结果离体灌流肾脏的肾小球滤过率,尿量,肾小管重吸收水、钠、葡萄糖百分率等肾功能参数在灌流的90min期间处于稳定的生理范围内;对照组灌流肾脏尿酸排泄分数、尿酸清除率及90min内总尿酸排泄量分别为30%、0.30ml.L-1和15μmol,与对照组比较,丙磺舒使离体肾脏尿酸排泄分别提高36%、54%和99%。结论离体大鼠肾脏灌流技术可用于发现和评价促尿酸排泄药物作用。     

Application of the axial dispersion model of hepatic drug elimination to the kinetics of diazepam in the isolated perfused rat liver

The application of the axial dispersion model to diazepam hepatic elimination was evaluated using data obtained for several conditions using the single-pass isolated perfused rat liver preparation. The influence of alterations in the fraction unbound in perfusate (fu) and perfusate flow (Q) on the availability (F) of diazepam was studied under steady conditions (n=4 in each case). Changes in fu were produced by altering the concentration of human serum albumin (HSA) in the perfusion medium while maintaining diazepam concentration at 1 mg L^–1. In the absence of protein (fu = 1), diazepam availability was 0.011 ±0.005 (¯x±SD). >As fu decreased, availability progressively increased and at a HSA concentration of 2% (g/100 ml), whenfu was 0.023, diazepam availability was 0.851 ±0.011. Application of the axial dispersion model to the relationship betweenfu andF provided estimates for the dispersion numbe (D _N) of 0.337±0.197, and intrinsic clearance (CL _int) of 132±34 ml min^–1. The availability of diazepam during perfusion with protein-free media was also studied at three different flow rates (15, 22.5, and 30 ml min^–1). Diazepam availability always progressively increased as perfusate flow increased, with the axial dispersion model yielding estimates forD _N of 0.393 ± 0.128 andCL _int of 144 ±38 ml min^–1. The transient form of the two-compartment dispersion model was also applied to the output concentration versus time profile of diazepam after bolus input of a radiolabeled tracer into the hepatic portal vein (n=4), providingD _N andCL _int estimates of 0.251 ±0.093 and 135±59 ml min^–1, respectively. Hence, all methods provided similar estimates forD _N andCL _int. Furthermore, the magnitude of D_Nis similar to that determined for noneliminated substances such as erythrocytes, albumin, sucrose, and water. These findings suggest that the dispersion of diazepam in the perfused rat liver is determined primarily by the architecture of the hepatic microvasculature.This work was supported by the Commission of the European Communities and the Medical Research Council. One of us (A.M.E.) was partially supported by a Merck, Sharp & Dohme Fellowship. We are grateful to Roche (Switzerland) for the supply of diazepam and 2-[¹⁴C]-diazepam, and Kabi AB (Sweden) for the supply of human serum albumin.     

Comparison of benzo(a)pyrene metabolism in isolated perfused rat lung and liver

The metabolism of 1 mM benzo(a)pyrene was studied in isolated perfused lung and liver of 5,6-benzoflavone-pretreated rats. Benzo(a)pyrene metabolism by the liver was more rapid than by the lung, but total metabolite formation in the lung at the end of a 120-min perfusion period was comparable to that in the liver. Lung perfusate was characterized by high concentrations of free metabolites, with diols outweighing phenols; in liver perfusate free metabolite concentrations were low, and large quantities of metabolites were found as conjugates in the bile at the end of perfusion. The tissue concentrations of free diols and phenols including the precursors of the main DNA-binding secondary metabolites were higher in the lung than in the liver. These findings explain the similar level of covalent binding in perfused lung and liver previously described (Klaus et al. 1982).Abbreviations Used BP benzo(a)pyrene - 9,10-diol 9,10-dihydro9,10-dihydroxy-benzo(a)pyrene - 4,5-diol 4,5-dihydro-4,5-dihydroxy-benzo(a)pyrene - 7,8-diol 7,8-dihydro-7,8-dihydroxy-benzo(a)pyrene - 9-OH 9-hydroxy-benzo(a)pyrene - 3-OH 3-hydroxybenzo(a)pyrene - tetrols 7,8,9,10-tetrahydro-7,8,9,10-tetrahydroxy-benzo(a)pyrenes - BF 5,6-benzoflavone - TLC thin-layer chromatography - HPLC high-pressure liquid chromatography     

Differential effects of uridine adenosine tetraphosphate on purinoceptors in the rat isolated perfused kidney

BACKGROUND AND PURPOSE

Purinergic signalling plays an important role in vascular tone regulation in humans. We have identified uridine adenosine tetraphosphate (Up₄A) as a novel and highly potent endothelial-derived contracting factor. Up₄A induces strong vasoconstrictive effects in the renal vascular system mainly by P2X₁ receptor activation. However, other purinoceptors are also involved and were analysed here.

EXPERIMENTAL APPROACH

The rat isolated perfused kidney was used to characterize vasoactive actions of Up₄A.

KEY RESULTS

After desensitization of the P2X₁ receptor by α,β-methylene ATP (α,β-meATP), Up₄A showed dose-dependent P2Y₂-mediated vasoconstriction. Continuous perfusion with Up₄A evoked a biphasic vasoconstrictor effect: there was a strong and rapidly desensitizing vasoconstriction, inhibited by P2X₁ receptor desensitization. In addition, there is a long-lasting P2Y₂-mediated vasoconstriction. This vasoconstriction could be blocked by suramin, but not by PPADS or reactive blue 2. In preparations of the rat isolated perfused kidney model with an elevated vascular tone, bolus application of Up₄A showed a dose-dependent vasoconstriction that was followed by a dose-dependent vasodilation. The vasoconstriction was in part sensitive to P2X₁ receptor desensitization by α,β-meATP, and the remaining P2Y₂-mediated vasoconstriction was only inhibited by suramin. The Up₄A-induced vasodilation depended on activation of nitric oxide synthases, and was mediated by P2Y₁ and P2Y₂ receptor activation.

CONCLUSIONS AND IMPLICATIONS

Up₄A activated P2X₁ and P2Y₂ receptors to act as a vasoconstrictor, whereas endothelium-dependent vasodilation was induced by P2Y_1/2 receptor activation. Up₄A might be of relevance in the physiology and pathophysiology of vascular tone regulation.     

Protein binding and hepatic clearance: Discrimination between models of hepatic clearance with diazepam,a drug of high intrinsic clearance,in the isolated perfused rat liver preparation

The influence of protein binding on the extraction ratio, and availability, of diazepam has been examined in the single-pass isolated perfused rat liver preparation. Binding of diazepam was varied by adjusting the concentration of albumin in the perfusate. In the absence of binding the extraction ratio of diazepam was high, 0.93–0.995. Extraction decreased dramatically as the degree of binding was increased. The data are more consistent with the parallel-tube model than with the well-stirred model, two perfusion models that have been used to describe hepatic drug elimination.     

Differential disposition of intra-renal generated and preformed glucuronides: studies with 4-methylumbelliferone and 4-methylumbelliferyl glucuronide in the filtering and nonfiltering isolated perfused rat kidney

Objectives This study was designed to investigate the renal disposition of 4‐methylumbelliferone (4MU) and 4‐methylumbelliferyl glucuronide (4MUG) to characterise the contribution of excretion and metabolic clearance to total clearance in the kidney. Methods The isolated perfused kidney (IPK) from the male Sprague–Dawley rat was used in filtering and non‐filtering mode to study the renal disposition of 4MU, renally generated 4MUG and preformed 4MUG. Perfusate and urine (filtering IPK only) was collected for up to 120 min and 4MU and 4MUG in perfusate and urine were determined by HPLC. Analytes were also measured in kidney tissue collected at 120 min. Non‐compartmental analysis was used to derive pharmacokinetic parameters. Key findings The concentration of 4MU in perfusate declined with a terminal half‐life of approximately 120 min following administration to the filtering IPK and nonfiltering IPK. There was a corresponding increase in the concentration of 4MUG. Metabolic clearance of 4MU accounted for 92% of total renal clearance. After bolus dosing of preformed 4MUG in the perfusion reservoir of the filtering IPK, the perfusate concentration declined with the terminal half‐life of approximately 260 min. The renal excretory clearance of preformed 4MUG accounted for 96% of total renal clearance. 4MU was extensively metabolized by glucuronidation in the filtering and nonfiltering IPK, and the total renal clearance of 4MU was far greater than its renal excretory clearance. This indicated that glucuronidation was the major elimination pathway for 4MU in the kidney. Conclusions The data confirmed an important role for the kidney in the metabolic clearance of xenobiotics via glucuronidation and signalled the lack of impact of impaired glomerular filtration on renal drug metabolism.     

Pharmacokinetics of the enantiomers of hexobarbital studied in the same intact rat and in the same isolated perfused rat liver

The pharmacokinetics of (+)- and (?)-hexobarbital were studied in the same intact rat after i.v. administration, as well as in the same isolated rat liver. The blood half-life of (+)-hexobarbital was 2–3 times shorter than than of (?)-hexobarbital, both in vivo and in vitro. No differences in apparent volume of distribution were observed, but the metabolic clearance of (+)-hexobarbital was 2–3 times greater. Clearance values in vivo were found to be equal to those in vitro for the same compound. No differences in binding to 3% albumin were observed at 3 physiological concentrations, determined by equilibrium dialysis. The animals slept much longer after injection of (+)-hexobarbital and the blood concentration at the moment of awakening was approximately 4 times lower than after injection of (?)-hexobarbital. It is suggested that a difference in anesthetic potency between the hexobarbital enantiomers at the CNS level is likely to exist.     

谷胱甘肽的肝脏转运及其在胆汁淤积中的作用

谷胱甘肽是一个由谷氨酸、半胱氨酸及甘氨酸组成的三肽, 具有抗氧化和解毒等功能。近年来研究发现谷胱甘肽的胆汁外排是生成非胆汁酸依赖型胆汁流的重要驱动力,谷胱甘肽的胆汁外排受阻可引起胆汁淤积。本文对谷胱甘肽的肝脏转运通路及其在胆汁淤积中的作用的研究进展进行综述。基于谷胱甘肽对胆汁流的驱动作用,增强谷胱甘肽的胆汁外排转运可望成为胆汁淤积防治的新靶点。     

地尔硫对大鼠离体肝脏灌流中安替比林代谢的影响

以安替比林（AP）为模型药,采用大鼠离体肝脏灌流模型（IPRL）,研究钙离子拮抗剂地尔硫本（DZ）对AP代谢的影响。方法：15只雄性Sprague-Dawley大鼠随机分为3组,A、B组灌胃（iP）生理盐水3d,第4天分别用5mgAP及加用2mgDZ循环灌流3h,C组ipDZ（100·kg-1）3d,第4天同B组灌流。HPLC法测定灌流液中AP及其代谢物的浓度。结果：B、C组中,AP的T1/2从（127．9±9.4）min分别延长至（2742±33.6）和（303.8±80．2）min（P＜0．01）;Cls从（0．67±0.08）ml·min－1分别减少至（0．36±0.06）和（0．34±0．09）ml·min－1（P＜0．01）;4-羟基AP的AUC0-3h分别降低73．95％和68.1％（P＜0．01）;3-羟甲基AP和N-去甲基AP和没有明显变化（P＞0．05）。结论：DZ明显抑制TAP在IPRL中的消除,且选择性地抑制AP的4-羟基化代谢途径。     

Protection by exogenous glutathione against hypoxic and cyanide-induced damage to isolated perfused rat livers

In experiments with isolated perfused livers from fasted rats, addition of 2 mmol/l glutathione (GSH) to the perfusion medium protected against hepatic damage induced by cyanide or hypoxia and reoxygenation as evidenced by leakage of lactate dehydrogenase and hepatic calcium accumulation. In control experiments as well as in experiments with cyanide or hypoxia and reoxygenation, exogenous glutathione resulted in an augmentation of cellular glutathione content, indicating either direct uptake of GSH or stimulation of its intracellular synthesis. The protective effects of glutathione against hypoxic and cyanide-induced hepatotoxicity substantiate the role of oxidative stress in both types of injury.     

Effects of gentamicin on renal function in isolated perfused kidneys from male and female rats

The isolated perfused rat kidney was used to determine whether sex differences in gentamicin nephrotoxicity are related to intrinsic differences in renal response to gentamicin. Acute exposure to gentamicin decreased fractional reabsorption of water and electrolytes without changes in glomerular filtration rate in both sexes. Gentamicin decreased the tubular reabsorption of lysozyme but not glomerular permeability to lysozyme. No sex differences in renal responses were observed following in vitro exposures to gentamicin, suggesting that sex differences in susceptibility to gentamicin in vivo may be attributable to extrarenal factors, such as pharmacokinetics.