Hypothermic Storage of Periportal and Perivenous Rat Hepatocytes

High yields of intact parenchymal cells are produced by the two-step Digitonin-collagenase perfusion of whole liver, and it has gained wide acceptance for biochemical and cellular analyses of zonal hepatocytes. The development reached by this methodology is in contrast to the time-limited use of the isolated cells unless those other methods, such as primary cultures, are employed. An alternative option to have cells ready to be used for several days, is the cold storage in University of Wisconsin solution as a preservation solution. This procedure is easy, not too expensive, and does not require specialized equipment. We study the competence of this system to maintain liver cells: mixed or total cells and cell-enriched fractions. We affirm viability of hepatocytes during hypothermic storage (UW-96h-4°C) by Trypan Blue exclusion, the capacity to retain cytoplasmic enzymes, metabolic competence to maintain total Glutathione content, and immunocytochemistry (gene detection). After 96 h of cold storage, mixed cells and cell-enriched fractions, were submitted to normothermic incubation (120 min, 37°C) and we check Trypan Blue exclusion, cytoplasmic enzyme release, and the capacity of cell populations to synthesize urea. The results show that it is possible to use, after several days of storage, mixed liver cells and cell-enriched fractions in metabolic and gene expression studies. This procedure allows us to reduce the number of experimental animals needed, to save experimental time and costs, and to facilitate further studies in vitro about the basis and consequences of metabolic heterogeneity of the liver cell plate.

Importance of pH in Resuspension Media on Viability of Hepatocytes Preserved in University of Wisconsin Solution

The effect of different pH of resuspension media on the viability of hepatocytes preserved (for 96 h at 4°C) in University of Wisconsin solution (UW solution) was analyzed. After this cold resuspension media storage, we evaluated the rewarming step (incubation time 120 min at 37°C) using different pH levels (6.80, 7.00, 7.20, and 7.40). Cell viability assessed by trypan blue exclusion (TBE) showed a significant difference (p < 0.05) for cells incubated at pH = 7.20. For instance, TBE expressed as percent of change was 78.1 ± 1.4 compared with cells tested at other pH (pH = 6.80, TBE = 44.2 ± 9.5; pH = 7.00, TBE = 66.5 ± 1.1 and pH = 7.40, TBE = 62.0 ± 1.4). We also evaluated the capacity of these cells both to maintain potassium content (0.509 ± 0.230 μEq. K+/106 cells) and to synthesize urea (5.36 ± 1.81 μmol Urea/106 cells). These results were compared with those obtained from freshly isolated non preserved hepatocytes (0.518 ± 0.060 μEq. K+/106 cells and 5.91 ± 0.43 μmol Urea/106 cells). The results show that viability is pH dependent and suggest that when resuspension media were used, the viability of hepatocytes was improved after 96 h of cold storage.

Protective Effect of Glutathione (GSH) over Glutathione Monoethyl-Ester (GSH-E) on Cold Preservation of Isolated Rat Liver Cells

Hepatocyte suspensions provide a rapid method to determine how hypothermic storage affects liver cell metabolism and viability. We investigated whether reduced Glutathione (GSH) inclusion into a modified University of Wisconsin (UW) solution, has a protective effect over Glutathione derivatives, such as Glutathione-monoethylester (GSH-E), when suspensions of hepatocytes are cold stored for several days. Isolated rat liver cells were cold preserved 96 h in UW, UW plus 3 mM GSH and UW plus 3 mM GSHE. During the cold storage, not significant changes in cell viability were observed, but the total Glutathione content was higher in systems with extracellular GSH over those with GSH-E or without. After cold storage, the liver cells were gently resuspended in Krebs-Henseleit — 1% Albumin and used for 120 min of normothermic (37°C) incubation. We evaluate the functional response of the cells measuring the exclusion of Trypan Blue (TBE). This response was clearly different in preserved cells in presence of GSH. These results indicate a protective role of extracellular Glutathione, due to an accumulation of it, rather than the derivative, for hepatic cell during the cold storage in UW solutions. And also, it is possible to extend experiments with hepatocytes from a single cell isolation over 4 or more consecutive days

Biopreservation of hepatocytes: current concepts on hypothermic preservation, cryopreservation, and vitrification

Isolated liver cells (primarily isolated hepatocytes) have found important applications in science and medicine over the past 40 years in a wide range of areas, including physiological studies, investigations on liver metabolism, organ preservation and drug de-toxification, experimental and clinical transplantation. An integral component of many of these works is the need to store the isolated cells, either for short or long-term periods. This review covers the biopreservation of liver cells, with a focus on the history of liver cell biopreservation, the application of hypothermia for short-term storage, standard cryopreservation methods for isolated hepatocytes, the biopreservation of other types of liver cells, and recent developments such as vitrification of hepatocytes. By understanding the basis for the different approaches, it will be possible to select the best options for liver cell biopreservation in different applications, and identify ways to improve preservation protocols for the future.

A device to record ultra-rapid cooling profiles

This work deals with the construction and performance of a measuring system capable of estimating temperature at sufficiently high speed (up to 1000 samples per sec). Due to its simple design and the utilization of standard materials, it could serve to recording the cooling profile of ultra-rapid procedures. An immersion device was also developed with the purpose of normalize the penetration speed of the sample in the LN2. The device allows also the comparative analysis of different cooling profiles. The system consists of an immersion device of the sample in the cooling agent, a temperature measurement system developed by Kleihans F and a laptop computer. To test the system, we recorded the cooling profiles of 10 uL of distilled water and 6 M glycerol solution, obtaining a cooling rate of 8732 C/min and 4441 C/min respectively. Also we determine a cooling rate of 204.012 C/min during the immersion of the thermocouple assembly in LN2. Although, the same device, with small technical modifications related to the handling of the sample, could be used to evaluate the recovery from LN2 temperature to room temperature (re-warming).

Protective effects of a carbon monoxide-releasing molecule (CORM-3) during hepatic cold preservation

There is increasing evidence that carbon monoxide (CO), a signaling molecule generated during the degradation of heme by heme oxygenase-1 (HO-1) in biological systems, has a variety of cytoprotective actions, including anti-hypoxic effects at low temperatures. However, during liver cold preservation, a direct effect needs to be established. Here, we designed a study to analyze the role of CO, delivered via a carbon monoxide-releasing molecule (CO-RM) in the maintenance of liver function, and integrity in rats during cold ischemia/reperfusion (CI/R) injury. We used an isolated normothermic perfused liver system (INPL) following a clinically relevant model of ex vivo 48 h cold ischemia stored in a modified University of Wisconsin (UW) solution, to determine the specific effects of CO in a rat model. CO was generated from 50 microM tricarbonylchloro ruthenium-glycinato (CORM-3), a water-soluble transition metal carbonyl that exerts pharmacological activities via the liberation of controlled amounts of CO in biological systems. The physiological effects of CORM-3 were confirmed by the parallel use of a specific inactive compound (iCORM-3), which does not liberate CO in the cellular environment. CORM-3 addition was found to prevent the injury caused by cold storage by improving significantly the perfusion flow during reperfusion (by almost 90%), and by decreasing the intrahepatic resistance (by 88%) when compared with livers cold preserved in UW alone. Also, CORM-3 supplementation preserved good metabolic capacity as indicated by hepatic oxygen consumption, glycogen content, and release of lactate dehydrogenase. Liver histology was also partially preserved by CORM-3 treatment.

CONCLUSIONS

These findings suggest that CO-RM could be utilized as adjuvant therapeutics in UW solutions to limit the injury sustained by donor livers during cold storage prior to transplantation, as has been similarly proposed for the heart, and kidney.

Effect of S-nitrosoglutathione (GSNO) added to the University of Wisconsin solution (UW): I) Morphological alteration during cold preservation/reperfusion of rat liver

Cold liver preservation in the University of Wisconsin solution (UW) followed by reperfusion alters hepatic parenchyma and stroma. In this study we demonstrated the benefit of adding S-nitrosoglutathione (GSNO) to the UW solution before cold storage, as an effective Nitric Oxide (NO) donor to prevent hepatic injury. Wistar adult rat livers were stored in UW solution (4 degrees C-48Hs) and then reperfused 60 minutes in the isolated perfused rat liver model (IPRL). Normal untreated livers and perfused livers, but not preserved were used as controls. Parenchymal damages were evaluated with Hematoxylin-Eosin stain and an inmunohistochemistry assay for albumin was used as functional test. To study the stroma, collagen type III and I networks were analyzed using Picro-sirius Red stain and Gordon Sweets' method for reticulin. After 48 Hs of cold preservation in UW solution livers showed few rounded endothelial cells inside sinusoidal lumen and extended areas of cell vacuolation. Albumin distribution was evident only around central veins and middle zones of the hepatic lobule. Collagens III and I networks were disorganized. When preserved with the addition of 100 microM GSNO and then reperfused, the hepatic morphology, in general, was conserved showing little vacuolation, fewer endothelial cells inside sinusoids and good albumin distribution around central veins and middle zones. The stroma had organized networks of collagen III and I. We concluded that the addition of 100 microM GSNO as a NO donor, can improve UW solution properties to preserve rat liver by maintaining the hepatic morphology and avoiding hepatic injury post cold preservation/reperfusion.

Glutathione synthesis during the rewarming of rat hepatocytes preserved in the University of Wisconsin solution

In this study, we used isolated rat hepatocytes to investigate the effect of nucleoside content of the preserved cells on the ability to synthesize glutathione (GSH) during the rewarming process. We cold-stored hepatocytes in University of Wisconsin (UW) solution (72 h, 0 degrees C, N(2)) without nucleosides and with the addition of 5 mM adenosine or 10 mM ATP. After 72 h of cold storage, we determined the GSH synthesis rate and the ATP content of the cells. We found a GSH synthesis rate similar to that of freshly isolated hepatocytes only in the group of cells cold-stored with 10 mM ATP. When we tested the cellular ATP concentrations, we found that controls and preserved cells with 10 mM ATP showed a similar value of ATP during the rewarming step. Our results suggested that the incorporation of ATP in the UW solution increased the ATP content and the rate of GSH synthesis of cold-stored hepatocytes during rewarming.

Glutathione content during the rinsing and rewarming process of rat hepatocytes preserved in University of Wisconsin solution

The addition of glutathione (GSH) to University of Wisconsin (UW) solution increases the intracellular content of GSH and decreases the release of lactate dehydrogenase used here as a measure of cell viability. However, we found a depletion of GSH when the cells were transferred from UW solution to the rewarming solution. This could sensitize the cells to various forms of oxidative injury. In this study we examined how different compositions of rinsing and rewarming solutions affected the GSH content and the viability of hepatocytes after 72 h of cold storage. For both the rinsing and the rewarming steps we used a Krebs-Henseleit solution with the addition of GSH, methionine, or both GSH and methionine. We found no loss of GSH when the hepatocytes were rinsed in the presence of 3 mM GSH. During the rewarming step we observed a loss of GSH in all of the study groups, but the cells that were incubated with 1 mM methionine showed a lesser depletion of GSH and improved viability. This finding may have valuable applications in hepatocellular transplantation and in the development of bioartificial liver support devices.

Uptake of [(3)H]bilirubin in freshly isolated rat hepatocytes: role of free bilirubin concentration

Hepatocytic transport of physiological concentrations of unconjugated bilirubin (UCB) has not been determined in isolated liver cells. Initial uptake of highly purified [(3)H]UCB was measured in rat hepatocytes in the presence of human serum albumin at various free, unbound UCB concentrations, [UCB]. At [UCB]=42 nM (below aqueous solubility of 70 nM), uptake was strictly temperature dependent; this was much less evident at [UCB]=166 nM (supersaturated). At low, physiological UCB concentrations, specific UCB uptake showed saturative kinetics with an apparent K(m) of 41 nM, indicating carrier-mediated transport. With aqueous supersaturation, UCB entered hepatocytes mainly by passive diffusion.

Role of sodium nitroprusside in the improvement of rat liver preservation in University of Wisconsin solution: A study in the isolated perfused liver model

BACKGROUND

Long-term liver preservation is needed to transform liver transplantation from an emergency operation into an elective procedure and, therefore, to improve the results of liver transplantation.

AIMS

We have studied the possibility of extending the period of cold ischemia of the rat liver, maintaining good hemodynamics and functional conditions, by adding the NO donor sodium nitroprusside (NPNa) to the preservation solution.

MATERIALS AND METHODS

Rat livers were preserved for 24, 48, and 72 h in University of Wisconsin solution (UW) at 4 degrees C (groups I, II, and III) or UW to which 500 microM NPNa was added (groups IV, V, and VI). Following the preservation time, liver viability was assessed using the isolated perfused liver model. Lactate dehydrogenase (LDH) and K(+) release, bile flow, and portal resistance were evaluated in each group and compared with those of liver controls (group VII) excised and perfused without preservation.

RESULTS

Some deleterious effects can be seen during cold storage conditions as assessed by an increment in intrahepatic resistance and a diminution in the capacity of the organ to produce bile. On histological observation, we see vacuolated hepatocytes and free endothelial cells (detached) in the sinusoidal lumen. Addition of 500 microM NPNa to UW significantly moderates these injuries, with an improvement in intrahepatic circulation (less intrahepatic resistance), an increment in bile production, and better histological appearance of the organ. We were also able to determine the capacity of the UW + NPNa to produce NO.

CONCLUSION

We assume that the beneficial vascular effects of NPNa are mediated by NO production.

Hypothermic storage of periportal and perivenous rat hepatocytes

High yields of intact parenchymal cells are produced by the two-step Digitonin-collagenase perfusion of whole liver, and it has gained wide acceptance for biochemical and cellular analyses of zonal hepatocytes. The development reached by this methodology is in contrast to the time-limited use of the isolated cells unless those other methods, such as primary cultures, are employed. An alternative option to have cells ready to be used for several days, is the cold storage in University of Wisconsin solution as a preservation solution. This procedure is easy, not too expensive, and does not require specialized equipment. We study the competence of this system to maintain liver cells: mixed or total cells and cell-enriched fractions. We affirm viability of hepatocytes during hypothermic storage (UW-96 h-4 degrees C) by Trypan Blue exclusion, the capacity to retain cytoplasmic enzymes, metabolic competence to maintain total Glutathione content, and immunocytochemistry (gene detection). After 96 h of cold storage, mixed cells and cell-enriched fractions, were submitted to normothermic incubation (120 min, 37 degrees C) and we check Trypan Blue exclusion, cytoplasmic enzyme release, and the capacity of cell populations to synthesize urea. The results show that it is possible to use, after several days of storage, mixed liver cells and cell-enriched fractions in metabolic and gene expression studies. This procedure allows us to reduce the number of experimental animals needed, to save experimental time and costs, and to facilitate further studies in vitro about the basis and consequences of metabolic heterogeneity of the liver cell plate.

Glutathione movements during cold preservation of rat hepatocytes

In this study we have examined the movements of glutathione (GSH) during cold preservation of rat hepatocytes in University of Wisconsin solution. During the preservation process at a low temperature (4 degrees C), with a high extracellular potassium concentration, an extracellular nondiffusible anion (lactobionate), and a Cl(-)-free medium, there is a depletion of metabolites and the development of a time-dependent injury. Also, there is a loss of GSH that is not compensated by transport or synthesis and is basically due to increased catabolic processes. This sensitizes the cells to different forms of oxidative injury, which can play a negative role during transplantation. The addition of GSH improves liver cell preservation but the mechanism is unclear. To elucidate this process we have isolated hepatocytes and preserved them under different conditions: with or without GSH: in the presence of DL-buthionine-[S,R]-sulfoximine, an inhibitor of glutathione synthetase, and acivicine to inhibit the ectoactivity of cellular gammaglutamyl transpeptidase; or by obtaining hepatocytes from rats depleted of GSH by an injection of diethyl maleate. Under all these conditions we evaluated the GSH content of the cells during cold storage. We also report the time course of accumulation of [glycine-2-3H]GSH. Our results show that during hypothermic storage in University of Wisconsin solution, hepatocytes are permeable to GSH, and the mechanism involved is a rapid nonsaturable process, with linear dependence of the extracellular GSH concentration. This finding may have valuable applications in the improvement of the delivery of compounds to cells.

Importance of pH in resuspension media on viability of hepatocytes preserved in University of Wisconsin solution

The effect of different pH of resuspension media on the viability of hepatocytes preserved (for 96 h at 4 degrees C) in University of Wisconsin solution (UW solution) was analyzed. After this cold resuspension media storage, we evaluated the rewarming step (incubation time 120 min at 37 degrees C) using different pH levels (6.80, 7.00, 7.20, and 7.40). Cell viability assessed by trypan blue exclusion (TBE) showed a significant difference (p < 0.05) for cells incubated at pH = 7.20. For instance, TBE expressed as percent of change was 78.1 +/- 1.4 compared with cells tested at other pH (pH = 6.80, TBE = 44.2 +/- 9.5; pH = 7.00, TBE = 66.5 +/- 1.1 and pH = 7.40, TBE = 62.0 +/- 1.4). We also evaluated the capacity of these cells both to maintain potassium content (0.509 +/- 0.230 microEq. K+/10(6) cells) and to synthesize urea (5.36 +/- 1.81 mumol Urea/10(6) cells). These results were compared with those obtained from freshly isolated non preserved hepatocytes (0.518 +/- 0.060 microEq. K+/10(6) cells and 5.91 +/- 0.43 mumol Urea/10(6) cells). The results show that viability is pH dependent and suggest that when resuspension media were used, the viability of hepatocytes was improved after 96 h of cold storage.

Early influence of aflatoxin B1 on the functional state of isolated rat hepatocytes

The early effects (60 min) of aflatoxin B1 (AFB1) on membrane permeability and carbohydrate metabolism of liver cells were studied in fresh suspensions of rat hepatocytes. Evaluation by trypan blue exclusion, enzyme leakage, glycogen synthesis or degradation, and glyconeogenesis were chosen as viability tests. The results obtained showed an increase of lactate dehydrogenase (LDH), alanine aminotransferase (GPT) and aspartate aminotransferase (GOT) released into the medium and also an increase in the number of stained cells. These changes were significant at about 18 nmol/10(6) cells of AFB1, while a remarkable effect of the toxin on glyconeogenesis and glycogen synthesis or degradation was observed at 9 nmol/10(6) cells, doses commonly used for in vitro studies.

Comparison of hepatic, renal and intestinal bilirubin UDP-glucuronyl transferase activities in rat microsomes

1. Bilirubin UDP-glucuronyltransferase activity and its dependence on substrate concentrations in rat liver, renal cortex and intestinal mucosa microsomes were studied. 2. Bilirubin monoglucuronide synthesis from unconjugated bilirubin was a higher capacity, lower affinity step in comparison with bilirubin diglucuronide formation in the three tissues tested. 3. Bilirubin glucuronide formation in liver microsomes showed a higher capacity but a lower affinity than extrahepatic ones. Renal cortex and intestinal mucosa exhibited similar kinetics parameters. 4. In vitro bilirubin glucuronidation in renal cortex and intestinal mucosa was quantitatively important as compared with the hepatic one.

Biochemical and morphometric analysis of the effect of spironolactone on the livers from immature and adult rats

Biochemical and morphometric studies were carried out to characterize the effect of spironolactone (SP) on liver tissue from immature and adult young rats: 1. The SP produced an increase in total protein in all the groups. 2. Hypertrophy in 24 days-old rats. 3. Hypertrophy and hyperplasia in 48 days-old rats. 4. The morphometric studies were correlated to the biochemical parameters.

Formation of bilirubin monoglucuronide and diglucuronide in isolated rat hepatocytes. Effect of spironolactone

The formation of bilirubin monoglucuronide (BMG) and diglucuronide (BDG) was studied in isolated rat hepatocytes with appropriate viability. Isolated cells were obtained from normal rats and from rats pretreated with spironolactone (SP). A fixed number of cells (4.8 X 10(6)) was incubated in a medium containing uridine diphosphoglucuronic acid (UDPGA, 3.4 mM) and bilirubin (11.3 microM, 29 microM, 50 microM and 81 microM) for different time intervals (from 0 to 25 min). The pellet of cells and the supernatant fraction were subjected to alkaline methanolysis, and the proportions of BMG and BDG were estimated by thin-layer chromatography. No conjugates were detected at time O or in the absence of UDPGA in the incubation system. BMG and BDG were detected after 2 min of incubation and then they increased up to 15 min of incubation. Both conjugates were mostly found in the supernatant fraction, and a predominance of BMG was apparent. Normal cells also synthesized increasing amounts of BMG and BDG with the increase of bilirubin substrate concentration up to 50 microM. When hepatocytes from SP-treated rats were used, a more rapid rate of glucuronidation, that was mainly produced at the expense of BMG found in the supernatant fraction, was clear. The results probably indicate that enzymic conversion of BMG to BDG may be rate limiting in isolated hepatocytes although other possible mechanisms were not excluded.

Effect of spironolactone on p-nitrophenol glucuronidation in isolated rat hepatocytes

The effect of spironolactone (SP) on p-nitrophenol (PNP) glucuronidation was studied in isolated rat hepatocytes with appropriate viability conditions. A significant increase of protein concentration and PNP glucuronidation was found in the hepatocytes from SP-treated rats. Increased enzyme activity apparently was related to the SP dose. The results favor the conclusion that SP may induce PNP glucuronidation in the hepatocyte.

Effect of spironolactone on bilirubin metabolism in rat liver and small intestinal mucosa

In vitro and in vivo experimental models were designed for the study of the effect of spironolactone (SP) on bilirubin metabolism in rat liver and small intestinal mucosa. In vitro studies included uptake of bilirubin by liver slices and intestinal sheets, determination of glucuronyltransferase activity in mucosal homogenates, and the handling of bilirubin by the isolated perfused liver after bilirubin overload. In vitro studies were carried out to measure the plasma disappearance rate of bilirubin and to determine the extent of bilirubin conjugation and biliary excretion of the pigment infused intravenously. The results obtained suggested that the mechanisms involved in the uptake of bilirubin by tissues were not influenced by SP pretreatment. Glucuronyltransferase activity in the small intestinal mucosa was significantly induced by SP, as previously observed in rat liver. Isolated perfused livers from SP-treated rats, as well as treated living rats, exhibited a greater than normal capacity for bilirubin excretion into bile at the expense of bilirubin diglucuronide. Conjugated bilirubin in the small intestinal mucosa of rats infused with unconjugated pigment was also increased after SP pretreatment. The results favoured the conclusion that SP is an inducer of bilirubin conjugation in the livers as well as in extrahepatic tissues, such as the small intestinal mucosa.