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J J Lemasters

Publications and source records attributed to J J Lemasters.

At least 127 records · Page 7Linked to original sources
PubMed1993

Intracellular pH and Ca2+ homeostasis in the pH paradox of reperfusion injury to neonatal rat cardiac myocytes.

Ischemia is characterized by anoxia and a large decrease of tissue pH. After a critical period of ischemia, reperfusion precipitates irreversible injury. Previous work showed that reperfusion injury to cultured neonatal myocytes was precipitated by a rapid return to physiological pH, a "pH paradox" (Bond, J., B. Herman, and J. Lemasters. Biochem. Biophys. Res. Commun. 179: 798-803, 1991). The aim of this study was to measure intracellular pH (pHi) and cytosolic free Ca2+ during the pH paradox of reperfusion injury to cultured neonatal rat cardiac myocytes. pHi and free Ca2+ were measured by ratio imaging of 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein and fura 2 fluorescence. To simulate ATP depletion and acidosis of ischemia, myocytes were incubated with 20 mM 2-deoxyglucose plus 2.5 mM NaCN at pH 6.2. During simulated ischemia, pHi dropped to < 6.5 and subsequently remained constant. During this time, some blebbing but little hypercontraction occurred. After 3 or 4 h of simulated ischemia, inhibitors were removed and cells were incubated at pH 7.4 to simulate reperfusion. pHi began to increase, blebbing accelerated, and myocytes hypercontracted. As pHi increased, viability was lost. The same occurred if pH was increased but metabolic inhibitors were not removed. Monensin, a Na(+)-H+ ionophore, accelerated the increase of pH after reperfusion and hastened cell killing. Hypercontraction, blebbing, and loss of viability did not occur when inhibitors were removed at pH 6.2 or in the presence of dimethylamiloride, an inhibitor of Na(+)-H+ exchange. Protection was associated with maintenance of an acidotic pHi. Free Ca2+ progressively increased during simulated ischemia. After simulated reperfusion, free Ca2+ increased further.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1993

Effect of short-term ethanol treatment on voltage-dependent calcium channels in Kupffer cells.

Kupffer cells, the resident hepatic macrophages, are activated by calcium, and several reports indicate that their function (e.g., phagocytosis and cytokine production) is altered by ethanol. We recently found that Kupffer cells contain L-type voltage-dependent Ca2+ channels. The purpose of this study, therefore, was to evaluate the effect of short-term ethanol treatment on voltage-dependent Ca2+ channels in Kupffer cells. Kupffer cells were isolated from rats 2 hr after intragastric administration of ethanol (5 gm/kg intragastrically). Cytosolic free calcium concentration of cultured Kupffer cells was measured with the fluorescent Ca2+ indicator fura-2. In Kupffer cells isolated from control rats, partial replacement of extracellular Na+ by K+ caused an increase in cytosolic free calcium concentration in a concentration-dependent manner (half-maximal effect was observed with 81 mmol/L K+), presumably because of membrane depolarization. Acute ethanol treatment in vivo shifted the concentration-response curve for K+ to the right (half-maximal effect was observed with 94 mmol/L K+) and reduced the maximal elevation of cytosolic free calcium concentration by means of K+. Significantly, the dihydropyridine-type calcium channel agonist BAY K 8644 (1 mumol/L) shifted the concentration-response curve for K+ to the left in control and ethanol-treated groups (half-maximal effect was observed with 61 and 77 mmol/L K+, respectively). Moreover, the dihydropyridine-type calcium channel blocker nitrendipine (10 mumol/L) prevented the increase in cytosolic free calcium concentration in both groups. When extracellular Ca2+ was omitted from the incubation medium, the increases in cytosolic free calcium concentration due to depolarization were prevented completely. However, direct addition of ethanol to the cell cultures was without effect.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1993

Activation of voltage-dependent calcium channels in Kupffer cells by chronic treatment with alcohol in the rat.

Calcium is essential for activation of Kupffer cells and it was recently reported that Kupffer cells contain L-type voltage-dependent Ca++ channels. The purpose of the present study was to evaluate the effect of chronic ethanol treatment on Ca++ channels. Kupffer cells were isolated from rats fed either a control liquid diet or a liquid ethanol-containing diet for 5 to 8 weeks. The cytosolic free calcium concentration ([Ca++]i) was measured in freshly isolated Kupffer cells with the fluorescent Ca++ indicator, fura-2. In Kupffer cells isolated from the control group, partial replacement of extracellular Na+ by K+ caused a concentration-dependent increase in [Ca++]i (half-maximal effect, 83 +/- 1 mM K+) presumably as a result of membrane depolarization. The concentration-response curve for K+ was shifted significantly (P < .01) to the left in cells isolated from ethanol-treated rats (half-maximal effect, 73 +/- 1 mM K+). When extracellular Ca++ was omitted from the incubation medium or the dihydropyridine-type calcium channel blocker nitrendipine (10 microM) was added, the increase in [Ca++]i caused by depolarization was prevented completely. Thus, these data indicate that chronic ethanol treatment in vivo makes L-type voltage-dependent Ca++ channels in Kupffer cells easier to open, a phenomenon that could be involved in the mechanism of alcoholic liver injury.

Alcoholism↗
PubMed1993

Mitochondrial and glycolytic dysfunction in lethal injury to hepatocytes by t-butylhydroperoxide: protection by fructose, cyclosporin A and trifluoperazine.

In isolated mitochondria, t-butylhydroperoxide (t-BuOOH) and other pro-oxidants cause a permeability transition characterized by increased permeability to small ions, swelling and loss of membrane potential. Cyclosporin A and trifluoperazine inhibit this permeability transition. Here, we investigated the role of the mitochondrial permeability transition in lethal cellular injury from t-BuOOH. Hepatocytes from fasted rats were isolated by collagenase perfusion, and cell viability was assessed by propidium iodide fluorescence. t-BuOOH caused dose- and time-dependent cell killing. Fructose, a substrate for glycolytic ATP formation, protected at lower (< or = 100 microM), but not at higher concentrations of t-BuOOH. In fructose-treated cells, oligomycin (10 micrograms/ml) delayed cell killing after 100 to 300 microM t-BuOOH, whereas cyclosporin A (0.5 microM) plus trifluoperazine (5 microM) even more potently reduced lethal injury. In hepatocyte suspensions, 100 microM t-BuOOH caused mitochondrial depolarization as determined by release of rhodamine 123. Cyclosporin A plus trifluoperazine in the presence of fructose substantially reduced release of rhodamine 123. Similarly, in single cultured hepatocytes viewed by laser scanning confocal microscopy, t-BuOOH caused leakage of rhodamine 123 from mitochondria, an event which preceded cell death and which was delayed by fructose in combination with cyclosporin A plus trifluoperazine. At 1 mM, t-BuOOH inhibited glycolysis, and fructose in combination with either oligomycin or cyclosporin A plus trifluoperazine had only a short-lived protective effect. In conclusion, t-BuOOH toxicity was progressive with increasing dosages. At low t-BuOOH (< or = 50 microM), mitochondrial ATP synthetic capacity was inhibited, but not uncoupled.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1992

Transient activation of hepatic glycogenolysis by thrombin in perfused rat livers.

Thrombin, a peptide with native protease activity, caused a rapid (less than 1 min) increase in glycogenolysis of about 30%, assessed from rates of production of glucose+lactate+pyruvate, and in oxygen uptake in perfused rat liver. These increases were followed by a rapid return to basal values within 5 min. The effect of thrombin on glycogenolysis was dose-dependent and was maximal at perfusate concentrations around 1 U/ml. Interestingly, the effect of thrombin on glycogenolysis could be elicited only once in any given liver. The activation of glycogenolysis by thrombin was diminished nearly 50% by prior infusion of the protease inhibitor, diisopropyl fluorophosphate (10 microM), and over 90% when thrombin was treated with diisopropyl fluorophosphate prior to infusion. The stimulation of glycogenolysis by thrombin could be detected in isolated hepatocytes or in livers stored for 24 h in cold Euro-Collins solution, a treatment which destroys endothelial cells. Further, thrombin stimulated production of prostaglandin D2 from arachidonic acid in cultured hepatic endothelial but not Kupffer cells. The effect of thrombin on carbohydrate output was also blocked by a phospholipase A2 inhibitor (quinacrine, 50 microM) and by an inhibitor of the cyclooxygenase (indomethacin, 20 microM), suggesting the involvement of cyclooxygenase in the mechanism of action of thrombin. In support of this idea, the transient kinetics of stimulation of glycogenolysis by thrombin and arachidonic acid was nearly identical to release of thromboxane B2 (80-420 pg/ml) and prostaglandin D2 (300-900 pg/ml) from the perfused liver. Further, a second addition of thrombin failed to increase thromboxane and prostaglandin D2 release as well as carbohydrate production, supporting a causal link between these phenomena. Taken together, these data support the hypothesis that thrombin interacts with receptors in the liver, possibly on endothelial cells, leading to activation of phospholipase A2 and subsequent transient production of prostaglandins and thromboxanes. These mediators subsequently interact with receptors on parenchymal cells, leading to a transient stimulation of glycogenolysis.

Animals↗
PubMed1992

Reperfusion rather than storage injury predominates following long-term (48 h) cold storage of grafts in UW solution: studies with Carolina Rinse in transplanted rat liver.

Both storage injury and reperfusion injury have been reported in association with liver transplantation; however, which predominates is not clear. Therefore, these studies were designed to evaluate whether Carolina Rinse, which minimizes reperfusion injury following orthotopic liver transplantation in the rat, would be effective after long-term (48 h) storage of grafts in University of Wisconsin (UW) cold storage solution where sufficient time for development of storage injury exists. Livers were rinsed with either Ringer's solution or Carolina Rinse solution immediately prior to completion of implantation surgery. In the Ringer's group, 30-day survival was high following 24 h of cold storage (4/5) but was very low after 48 h (1/16). Importantly, survival was increased significantly (5/14) when grafts were rinsed with Carolina Rinse following 48 h of cold storage. In both groups, parenchymal cells appeared normal by scanning electron microscopy, excluded trypan blue, and released SGOT at values only slightly above the normal range immediately (i.e., less than 5 min) after 48 h of cold storage. However, SGOT values rose steadily during the 1st hour postoperatively following reperfusion in the Ringer's rinse group and reached levels around 1,000 U/l. In addition, nonparenchymal cells were not labelled with trypan blue following storage, but significant labelling occurred within 1 h. Both SGOT release and nonparenchymal cell injury were reduced significantly when grafts were rinsed with Carolina Rinse prior to completion of surgery. Liver injury assessed histologically 24 h postoperatively was also reduced about 50% by Carolina Rinse. Oxidative stress appeared to be involved, since radical adducts, most likely of lipid origin, were trapped during the first 5 min after reperfusion with the spin trapping technique and detected by electron paramagnetic resonance spectroscopy. Lipid radical formation was reduced nearly completely on reperfusion by Carolina Rinse. Since Carolina Rinse improved survival of liver grafts following long periods of cold storage and reduced lipid radical formation and hepatocellular injury, we concluded that a reperfusion injury rather than a storage injury predominates following orthotopic transplantation of livers stored for long periods of time in cold UW solution.

Adenosine↗
PubMed1992

Protection by pentoxifylline against graft failure from storage injury after orthotopic rat liver transplantation with arterialization.

Destruction of the endothelial cell lining and activation of Kupffer cells after reperfusion limits the safe storage of livers for transplantation surgery. Tumor necrosis factor-alpha (TNF) release by activated Kupffer cells may contribute to graft failure from storage injury. Accordingly, we evaluated whether pentoxifylline, which suppresses macrophage TNF release, would improve graft survival after orthotopic rat liver transplantation with arterialization. Livers from syngeneic Lewis rats were stored for 12-24 h in cold UW solution. Prior to implantation, the livers were flushed with cold Ringer's solution or warm Carolina rinse solution B. With either rinse, pentoxifylline treatment of graft recipients significantly improved graft survival. Combined use of pentoxifylline (50 mg/kg for 5 days) and Carolina rinse solution doubled the safe storage time to 24 h. Acidotic pH and antioxidants were essential components of Carolina rinse solution that acted synergistically with pentoxifylline. Pentoxifylline was also shown to suppress TNF release by lipopolysaccharide (LPS)-stimulated cultured rat Kupffer cells. Thus, pentoxifylline may protect against primary non-function and failure of grafts from storage injury by suppressing excessive TNF release by activated Kupffer cells. However, neutralization of TNF with excess anti-TNF antibody did not improve survival. This may mean that depletion of TNF is as deleterious as excess TNF production. Alternatively, other Kupffer cell secretions [e.g., interleukin-1 (IL-1), interleukin-6 (IL-6) and other cytokines] may be involved in the pathogenesis of graft failure. In conclusion, pentoxifylline could protect against graft failure from storage injury.

Animals↗
PubMed1992

The second generation of Carolina Rinse, solution II, improves graft survival following orthotopic liver transplantation in the rat by preventing reperfusion injury.

Carolina Rinse solution was designed to minimize reperfusion injury following orthotopic liver transplantation. Carolina Rinse blocks reperfusion-induced endothelial cell killing, diminishes postoperative enzyme release and improves survival dramatically. Adenosine and mildly acidotic pH were identified as key components. Here we report results with a simplified formulation, Carolina Rinse II, which contains extracellular inorganic ions similar to Ringer's solution, adenosine, as well as antioxidants and radical scavengers (allopurinol, glutathione and desferrioxamine). In this study, 44 rat livers were explanted and stored for 12 h in University of Wisconsin (UW) cold storage solution (non-survival conditions). Control livers were rinsed with 15 ml cold Ringer's solution just prior to completion of implantation surgery. In this control group, average 30-day survival was poor (8%). However, survival was increased to around 60% when grafts were rinsed with Carolina Rinse II. Survival was not improved significantly by rinsing the graft with Ringer's solution containing antioxidants and radical scavengers with adenosine omitted (about 30%). Peak SGOT values of nearly 3000 U/l, measured 1-3 days postoperatively in the Ringer's rinse control group, were decreased 4- to 5-fold both by Carolina Rinse II and by Ringer's solution containing antioxidants. On the other hand, the addition of adenosine to Ringer's solution improved survival (around 60%) but did not decrease the postoperative elevation of serum enzymes significantly. Thus, it appears that adenosine was necessary for optimal survival whereas antioxidants and radical scavengers were needed to prevent injury to the transplanted graft. These data were consistent with the hypothesis that at least two mechanisms, one involving the liver and a second one non-hepatic, are responsible for post-transplant pathophysiology. Carolina Rinse II also reduced the postoperative elevation in serum enzymes 2- to 3-fold in livers stored under survival conditions (e.g., for 8 h in UW solution). This study demonstrated convincingly that a very simple rinse solution, Carolina Rinse II, improved survival significantly and minimized graft injury following orthotopic liver transplantation.

Animals↗
PubMed1992

The calcium channel blocker nisoldipine minimizes the release of tumor necrosis factor and interleukin-6 following rat liver transplantation.

Kupffer cells, when activated, release toxic cytokines such as tumor necrosis factor (TNF), which can cause tissue injury. Takei et al. have reported that nisoldipine, a calcium channel blocker which decreases phagocytotic activity by Kupffer cells, also diminishes liver and lung injury and dramatically improves survival following liver transplantation. Therefore, we studied the effect of nisoldipine on the time course of TNF and interleukin-6 (IL-6) release following cold storage and liver transplantation in the rat. Livers were stored under survival and non-survival conditions in cold Euro-Collins solution in the presence or absence of nisoldipine (1.4 microM). After storage, the effluent was collected for determination of cytokines. The liver was then transplanted orthotopically and serum was collected at various time intervals for up to 5 h. In the effluent, TNF levels were very low in both the control and nisoldipine-treated groups and IL-6 was not measurable. Furthermore, when livers were stored under survival conditions and transplanted (liver stored in the cold for 4 h), serum TNF (2 U/ml) and IL-6 (350 U/ml) values were minimal in both the control and nisoldipine-treated groups. In contrast, when livers were stored under non-survival conditions and transplanted (liver stored in the cold for 10 h), TNF levels increased to 15 +/- 2 U/ml, 150 min after graft reperfusion, an increase which was prevented by nisoldipine (6.5 U/ml). Serum IL-6 levels were also elevated 300 min after transplantation in livers stored for 10 h. Nisoldipine also reduced the release of this cytokine. Serum transaminases (SGOT) were elevated to values around 2000 U/l 5 h following transplantation. In the nisoldipine-treated group, values were lower between 60 and 300 min. In the lung, interstitial and alveolar edema and cellular infiltration were detectable 5 h postoperatively and were diminished by nisoldipine. These data confirmed that TNF and IL-6 release were minimal following cold storage and transplantation of livers stored under survival conditions, but were elevated transiently after transplantation under non-survival conditions. Nisoldipine prevented cytokine release, most likely by blocking the activation of Kupffer cells, which may explain how it decreases liver and lung injury very early following liver transplantation.

Animals↗
PubMed1992

Warm Carolina rinse solution prevents graft failure from storage injury after orthotopic rat liver transplantation with arterialization.

An injury to nonparenchymal cells, characterized by loss of viability of sinusoidal endothelial cells and activation of Kupffer cells, occurs after reperfusion of livers stored for transplantation. Recently, a new solution, Carolina rinse solution, was shown to prevent reperfusion injury to endothelial cells in vitro almost completely and to improve graft survival after orthotopic rat liver transplantation (ORLT) without arterialization. ORLT with arterialization permits longer cold storage of donor livers and more closely models human surgery. Therefore, we evaluated the effects of Carolina rinse solution on graft survival after ORLT with arterialization in syngeneic Lewis rats. Just prior to implantation, donor livers stored in University of Wisconsin (UW) solution were rinsed with 30 ml of Ringer's solution, saline, or Carolina rinse solution at 1 degree-4 degrees C. In livers stored for 15 h and rinsed with Ringer's or saline solution, long-term graft survival was only 8%. Using Carolina rinse solution containing 1 mmol and 200 mumol adenosine per liter, graft survival improved to 40% and 80%, respectively. Graft survival did not improve when using Carolina rinse solution with adenosine omitted or Ringer's solution containing 200 mumol adenosine per liter. Livers were also rinsed with Carolina rinse solution containing 200 mumol adenosine per liter at 28 degrees-30 degrees C rather than at 1 degree-4 degrees C. With warm Carolina rinse solution, survival improved further to 100%, 80%, and 50% after 15, 18, and 21 h of storage. After 18 h of storage, light and electron microscopy demonstrated marked denudation of the sinusoidal lining and activation of Kupffer cells in grafts rinsed with Ringer's solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1992

A novel cytotoxicity screening assay using a multiwell fluorescence scanner.

A new assay using a multiwell fluorescence scanner was developed for screening cytotoxicity to cells cultured in 96-well microtiter plates. The assay is based on binding of propidium iodide to nuclei of cells whose plasma membranes have become permeable due to cell death. Fluorescence of propidium iodide measured with a multiwell fluorescence scanner increased in proportion to the number of permeabilized cells. After ATP depletion of hepatocytes and neonatal cardiac myocytes with metabolic inhibitors ("chemical hypoxia"), and exposure of Madine Darby canine kidney cells to the toxic chemical, HgCl2, propidium iodide fluorescence progressively increased. Increases of fluorescence were linearly proportional with release of lactate dehydrogenase into the culture medium. Employing this cytotoxicity screening assay, protection by various agents against lethal injury was evaluated in cultured hepatocytes during chemical hypoxia. Inhibitors of cysteine proteases (i.e., antipain, leupeptin, E-64), serine proteases (i.e., PMSF), and aspartic acid proteases (i.e., pepstatin A) did not protect against chemical hypoxia. In contrast, 1,10-phenanthroline, an inhibitor of metalloprotease, markedly protected against the onset of cell death during chemical hypoxia. Half-maximal protection after 60 min occurred at 0.5 microM. Phospholipase inhibitors, chlorpromazine (50 microM) and mepacrine (50 microM), also substantially retarded cell killing. U74006F, an inhibitor of lipid peroxidation, slowed cell killing to a lesser extent during chemical hypoxia and after oxidative stress with t-butyl hydroperoxide. Calciphor, a dimer of prostaglandin B1, did not protect against cell killing during chemical hypoxia or t-butyl hydroperoxide toxicity. In conclusion, this high capacity cytotoxicity assay for cells cultured in 96-well microtiter plates is suitable for rapid screening of potential cytoprotective agents in a variety of cell types.

Animals↗
PubMed1992

Evidence that free radicals are involved in graft failure following orthotopic liver transplantation in the rat--an electron paramagnetic resonance spin trapping study.

The purpose of these studies was to determine whether free radicals were formed as a consequence of reperfusion during orthotopic liver transplantation and whether their formation was related to graft failure. Grafts were stored for 18 hr in Euro-Collins solution or for 48 hr in University of Wisconsin solution (nonsurvival conditions) and reperfused with blood containing the spin trap alpha-phenyl N-tert-butylnitrone (PBN). Venous blood samples (4-5 ml) were collected, and serum was extracted with chloroform and methanol (2:1) and analyzed for radical adducts by electron paramagnetic resonance (EPR) spectroscopy. In samples from livers stored under nonsurvival conditions, EPR spectra were detected indicating the presence of PBN radical adducts. In contrast, radical adduct formation was 3- to 4-fold lower in similar experiments performed with untransplanted livers or with livers stored under survival conditions (1 hr in Ringer's solution or 24 hr in UW solution). Oxygen radicals are more likely involved in the production of radical adducts because formation was nearly completely prevented by superoxide dismutase plus catalase or Carolina rinse, which contains glutathione, desferrioxamine mesylate, and allopurinol. Radical adduct formation was much greater in a blood-free perfusion system where oxygen delivery was high, suggesting that blood elements are not necessary for radical adduct formation. An inverse correlation between survival of livers stored in UW solution and radical adduct signal was observed in this study. Thus, it is concluded that free radicals formed during reperfusion are involved in the mechanism of graft failure following liver transplantation in the rat.

Animals↗
PubMed1992

Activation of Kupffer cells on reperfusion following hypoxia: particle phagocytosis in a low-flow, reflow model.

Hypoxia is produced selectively in pericentral regions of the liver lobule with a low-flow, reflow perfusion model in which the flow rate is reduced to approximately one-third to one-fourth of normal. This model was used to monitor carbon particle phagocytosis by Kupffer cells during hypoxia and reoxygenation. At normal flow rates, oxygen uptake was 131 mumol.g-1.h-1, pressure was 7.5 cmH2O, and carbon uptake was 150 mg.g-1.h-1. During the low-flow period, oxygen uptake, pressure, and carbon uptake decreased to values of 54 mumol.g-1.h-1, 6.4 cmH2O and 83 mg.g-1.h-1, respectively. Upon reflow, oxygen uptake and pressure increased to 141 mumol.g-1.h-1 and 10.3 cmH2O, respectively. In addition, carbon uptake was elevated approximately threefold to 234 mg.g-1.h-1, indicating activation of Kupffer cells. This activation was prevented by pretreatment with methyl palmitate, a known inhibitor of Kupffer cells. Histological examination revealed significantly more Kupffer cells laden with carbon particles in untreated livers after reflow than in livers from methyl palmitate-treated or untreated rats. Electron microscopic analysis of livers at reflow revealed Kupffer cells with numerous pseudopodia and lamellapodia, reflecting an activated state. These changes were absent in controls or in livers perfused under low-flow conditions. This study demonstrates that Kupffer cells are activated on reoxygenation after hypoxia.

Animals↗
PubMed1992

Kupffer cells contain voltage-dependent calcium channels.

Kupffer cells, the resident hepatic macrophages, are activated by calcium, but conclusive evidence that they contain voltage-dependent calcium channels has not been presented previously. In this study, the cytosolic free calcium concentration ([Ca2+]i) of cultured Kupffer cells was measured with the fluorescent Ca2+ indicator fura-2. Partial replacement of extracellular Na+ by K+ caused an increase in [Ca2+]i in a concentration-dependent manner (half-maximal effect at 81 mM K+), presumably due to membrane depolarization. At 65 mM K+, where there were minimal changes in [Ca2+]i, addition of the dihydropyridine-type calcium channel agonist BAY K 8644 (1 microM) caused a large increase in [Ca2+]i. Overall, the effect of BAY K 8644 (1 microM) was to shift the concentration-response curve for K+ to the left (half-maximal effect at 61 mM K+). Under depolarizing conditions (65 mM K+), BAY K 8644 increased [Ca2+]i in a concentration-dependent manner (half-maximal effect at approximately 400 nM BAY K 8644). Moreover, the dihydropyridine-type calcium channel blocker nitrendipine inhibited the BAY K 8644-induced increase in [Ca2+]i in a concentration-dependent manner (half-maximal inhibition with about 25 nM nitrendipine). When extracellular Ca2+ was omitted from the incubation medium, the increases in [Ca2+]i due to BAY K 8644 were prevented completely. In addition, an intracellular Ca2+ antagonist, 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride (200 microM), did not inhibit the BAY K 8644-sensitive, voltage-dependent increase in [Ca2+]i. Thus, these data collectively indicate that BAY K 8644 causes a transmembrane Ca2+ influx in Kupffer cells in a voltage-dependent manner, providing the first direct evidence that Kupffer cells contain L-type voltage-dependent Ca2+ channels.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

Synergism of cyclosporin A and phospholipase inhibitors in protection against lethal injury to rat hepatocytes from oxidant chemicals.

Cyclosporin A and phospholipase inhibitors block the oxidant-induced mitochondrial permeability transition. Here, protection by these agents against cytotoxicity of oxidant chemicals was evaluated in rat hepatocytes. The combination of cyclosporin A and a phospholipase inhibitor (trifluoperazine, mepacrine, or dibucaine), but neither alone, substantially protected against lethal injury from 0.5 mM iodoacetate but had little effect against iodoacetate plus 2.5 mM KCN. Against 100 microM t-butylhydroperoxide, cyclosporin A and trifluoperazine protected only if fructose was present. Cyclosporin A plus phospholipase inhibition protected slightly against 2.5 mM cystamine, but actually increased lethal injury after 100 microM menadione. These effects are consistent with an oxidant-induced mitochondrial permeability transition that accelerates cell killing after iodoacetate and t-butylhydroperoxide.

Animals↗