Ischemic preconditioning in rats: role of mitochondrial K(ATP) channel in preservation of mitochondrial function

We examined the role of the sarcolemmal and mitochondrial K(ATP) channels in a rat model of ischemic preconditioning (IPC). Infarct size was expressed as a percentage of the area at risk (IS/AAR). IPC significantly reduced infarct size (7 +/- 1%) versus control (56 +/- 1%). The sarcolemmal K(ATP) channel-selective antagonist HMR-1098 administered before IPC did not significantly attenuate cardioprotection. However, pretreatment with the mitochondrial K(ATP) channel-selective antagonist 5-hydroxydecanoic acid (5-HD) 5 min before IPC partially abolished cardioprotection (40 +/- 1%). Diazoxide (10 mg/kg iv) also reduced IS/AAR (36.2 +/- 4.8%), but this effect was abolished by 5-HD. As an index of mitochondrial bioenergetic function, the rate of ATP synthesis in the AAR was examined. Untreated animals synthesized ATP at 2.12 +/- 0.30 micromol x min(-1) x mg mitochondrial protein(-1). Rats subjected to ischemia-reperfusion synthesized ATP at 0.67 +/- 0.06 micromol x min(-1) x mg mitochondrial protein(-1). IPC significantly increased ATP synthesis to 1.86 +/- 0.23 micromol x min(-1) x mg mitochondrial protein(-1). However, when 5-HD was administered before IPC, the preservation of ATP synthesis was attenuated (1.18 +/- 0.15 micromol x min(-1) x mg mitochondrial protein(-1)). These data are consistent with the notion that inhibition of mitochondrial K(ATP) channels attenuates IPC by reducing IPC-induced protection of mitochondrial function.     

Protective effect of liver ischemic preconditioning on rat hepatocytes

Ischemic preconditioning (IPC) protects liver graft function following ischemia in liver transplantation and liver resection. The aim of this study was to assess the advantages and any potential disadvantages of liver IPC prior to isolation for rat hepatocytes during isolation and cryopreservation. After isolating and thawing the cryopreserved hepatocytes after 14 and 28 d,cell viability,efficiency,and lactate dehydrogenase (LDH) levels in preserve solution were examined for every group. Groups treated with...     

Involvement of the mitochondrial calcium uniporter in cardioprotection by ischemic preconditioning

The objective of the present study was to determine whether the mitochondrial calcium uniporter plays a role in the cardioprotection induced by ischemic preconditioning (IPC). Isolated rat hearts were subjected to 30 min of regional ischemia by ligation of the left anterior descending artery followed by 120 min of reperfusion. IPC was achieved by two 5-min periods of global ischemia separated by 5 min of reperfusion. IPC reduced the infarct size and lactate dehydrogenase release in coronary effluent, which was associated with improved recovery of left ventricular contractility. Treatment with ruthenium red (RR, 5 μM), an inhibitor of the uniporter, or with Ru360 (10 μM), a highly specific uniporter inhibitor, provided cardioprotective effects like those of IPC. The cardioprotection induced by IPC was abolished by spermine (20 μM), an activator of the uniporter. Cyclosporin A (CsA, 0.2 μM), an inhibitor of the mitochondrial permeability transition pore, reversed the effects caused by spermine. In mitochondria isolated from untreated hearts, both Ru360 (10 μM) and RR (1 μM) decreased pore opening, while spermine (20 μM) increased pore opening which was blocked by CsA (0.2 μM). In mitochondria from preconditioned hearts, the opening of the pore was inhibited, but this inhibition did not occur in the mitochondria from hearts treated with IPC plus spermine. These results indicate that the mitochondrial calcium uniporter is involved in the cardioprotection conferred by ischemic preconditioning.     

Generation of hypochlorite-modified proteins by neutrophils during ischemia-reperfusion injury in rat liver: attenuation by ischemic preconditioning

Although it is well documented that neutrophils are critical for the delayed phase of hepatic ischemia-reperfusion injury, there is no direct evidence for a specific neutrophil-derived oxidant stress in vivo. Therefore, we used a model of 60 min of partial hepatic ischemia and 0-24 h of reperfusion to investigate neutrophil accumulation and to analyze biomarkers for a general oxidant stress [glutathione disulfide (GSSG) and malondialdehyde (MDA)] and for a neutrophil-specific oxidant stress [hypochlorite (HOCl)-modified epitopes] in rats. Plasma alanine transaminase activities and histology showed progressively increasing liver injury during reperfusion, when hepatic GSSG and soluble MDA levels were elevated. At that time, few neutrophils were present in sinusoids. However, the number of hepatocytes positively stained for HOCl-modified epitopes increased from 6 to 24 h of reperfusion, which correlated with the bulk of hepatic neutrophil accumulation and extravasation into the parenchyma. Consistent with a higher oxidant stress at later times, hepatic GSSG and protein-bound MDA levels further increased. Treatment with the NADPH oxidase inhibitor diphenyleneiodonium chloride attenuated postischemic oxidant stress (GSSG, protein-bound MDA, and hepatocytes positively stained for HOCl-modified epitopes) and liver injury at 24 h of reperfusion. Ischemic preconditioning suppressed all oxidant stress biomarkers, liver injury, and extravasation of neutrophils. In conclusion, extravasated neutrophils generate HOCl, which diffuses into hepatocytes and causes oxidative modifications of intracellular proteins during the neutrophil-mediated reperfusion injury phase. Ischemic preconditioning is an effective intervention for reduction of the overall inflammatory response and, in particular, for limitation of the cytotoxic activity of neutrophils during the later reperfusion period.     

Minimal protection of the liver by ischemic preconditioning in pigs

Ischemic preconditioning (IP) protects the rat liver. In pigs, in which hepatic tolerance to ischemia is similar to that in humans, information on IP is lacking. Therefore, in enflurane-anesthetized pigs, hepatic vessels were occluded for 120 min (protocol 1) or 200 min (protocol 2) without (control) and with IP (3 times 10 min ischemia-reperfusion each). In protocol 1, cumulative bile flow (CBF) during reperfusion was greater in IP (47.3 +/- 5.2 ml/8 h) than in control (17.1 +/- 7.8 ml/8 h, P < 0.05). ATP content tended to recover toward normal during reperfusion in IP, whereas it remained at ischemic levels in control. Serum enzyme concentrations increased similarly during reperfusion, and <1% hepatocytes were necrotic or stained terminal deosynucleotidyl transferase-mediated dUTP nick-end labeling-positive in control and IP groups. In protocol 2, no differences in CBF, ATP, or serum enzyme concentrations during reperfusion were measured between control and IP groups, except for a somewhat reduced lactate dehydrogenase in IP. The number of necrotic or terminal deosynucleotidyl transferase-mediated dUTP nick-end labeling-positive hepatocytes tended to be greater in the IP than the control group. Thus IP provides some functional protection against reversible ischemia but no protection during prolonged ischemia in pigs.     

Mechanism of alterations in isolated rat liver mitochondrial function induced by gold complexes of bidentate phosphines

Au(DPPE)+2 (bis[1,2-bis(diphenylphosphino)ethane] gold(I] is an organo-gold antineoplastic agent that has anti-tumor activity in a variety of in vitro cell lines and in vivo rodent tumor models. Preliminary studies suggested that this compound represented a novel class of inhibitors of mitochondrial function. The purpose of this study was, therefore, to determine the mechanism of mitochondrial dysfunction induced by Au(DPPE)+2. Au(DPPE)+2 induced a rapid, dose-related collapse of the inner mitochondrial membrane potential (EC50 = 28.0 microM) that was not potentiated by Ca2+ preloading. Au(DPPE)+2-induced dissipation of mitochondrial membrane potential was accompanied by an efflux of Ca2+ from mitochondria upon exposure to Au(DPPE)+2. Ca2+ efflux in these experiments was via a reversal of the Ca2+ uniporter as efflux could be inhibited with ruthenium red. Au(DPPE)+2 did not increase the permeability of mitochondria to oxalacetate, indicating that the collapse of membrane potential may not be a result of gross increased inner membrane permeability. However, Au(DPPE)+2 may mediate an increased permeability of the inner membrane to cations and protons. Au(DPPE)+2 caused passive swelling in potassium acetate buffer in the absence of valinomycin, suggesting Au(DPPE)+2 facilitated the exchange of H+ and K+. Ca2+ cycling was not extensive and did not contribute to the decrease in membrane potential. These data suggest that one possible mechanism of Au(DPPE+2-induced uncoupling of mitochondrial oxidative phosphorylation is via increased permeability of the inner mitochondrial membrane to cations. The disruption of mitochondrial function may be a key process leading to hepatocyte cell injury by this drug.     

Translocation of HSP27 to sarcomere induced by ischemic preconditioning in isolated rat hearts

We investigated the role of the 27-kDa heat shock protein (HSP27) in cardiac protection using Langendorff-perfused rat hearts. After preconditioning (a single episode of 5 min global ischemia followed by 5 min of reperfusion), HSP27 redistributed from the cytosol to the sarcomere and recovery of the contractile function, after 40 min of global ischemia and 50 min of reperfusion, was significantly enhanced. Both SB203580, a p38 MAP kinase inhibitor, and bisindolylmaleimide I, a protein kinase C inhibitor, prevented the effects of preconditioning. Both 2-chloro-N(6)-cyclopentyladenosine (adenosine A1 agonist) and anisomycin (activator of p38 MAP kinase and c-jun N-terminal kinase) mimicked preconditioning. These results suggest that activation of protein kinase C followed by activation of p38 MAP kinase elicits translocation of HSP27 to the sarcomere, a process which may be involved in the cardioprotective mechanism afforded by ischemic preconditioning in rat heart.     

Attenuation of mitochondrial injury by L-arginine preconditioning of the liver

The present study was aimed to evaluate the efficacy of L-arginine on mitochondrial function in ischemic and reperfusion (I/R) induced hepatic injury. Adult Wistar rat were subjected to 1 h of partial liver ischemia followed by 3 hour reperfusion. Eighteen wistar rats were divided into three groups viz. sham-operated control group (I) (n = 6), ischemia and reperfusion (I/R) group (II) (n = 6), L-arginine treated group (100 mg/kg body weight/daily by oral route for 7 days before induced ischemia reperfusion maneuver) (III) (n = 6). Mitochondrial injury was assessed in terms of decreased (P < 0.05) activities of mitochondrial antioxidant enzymes (GSH, SOD, CAT), respiratory marker enzymes (NADH dehydrogenase, cytochrome c oxidases) and hepatocytes nitric oxide production. Pre-treatment with L-arginine (10 mg/kg/p.o. for 7 days) significantly counteracted the alternations of hepatic enzymes and mitochondrial respiratory and antioxidant enzymes. In addition, electron microscopy and histopathology study showed the restoration of cellular normalcy and accredits the cytoprotective role of L-arginine against I/R induced hepatocellular injury. On the basis of these findings it may be concluded that L-arginine protects mitochondrial function in hepatic ischemic and reperfused liver.     

Inhibition of mitochondrial function in isolated rat liver mitochondria by azole antifungals

Ketoconazole is an imidazole oral antifungal agent with a broad spectrum of activity. Ketoconazole has been reported to cause liver damage, but the mechanism is unknown. However, ketoconazole and a related drug, miconazole, have been shown to have inhibitory effects on oxidative phosphorylation in fungi. Fluconazole, another orally administered antifungal azole, has also been reported to cause liver damage despite its supposedly low toxicity profile. The primary objective of this study was to evaluate the metabolic integrity of adult rat liver mitochondria after exposure to ketoconazole, miconazole, fluconazole, and the deacetylated metabolite of ketoconazole by measuring ADP-dependent oxygen uptake polarographically and succinate dehydrogenase activity spectrophotometrically. Ketoconazole, N-deacetyl ketoconazole, and miconazole inhibited glutamate-malate oxidation in a dose-dependent manner such that the 50% inhibitory concentration (I₅₀ was 32, 300, and 110 μM, respectively. In addition, the effect of ketoconazole, miconazole, and fluconazole on phosphorylation coupled to the oxidation of pyruvate/malate, ornithine/malate, arginine/malate, and succinate was evaluated. The results demonstrated that ketoconazole and miconazole produced a dose-dependent inhibition of NADH oxidase in which ketoconazole was the most potent inhibitor. Fluconazole had minimal inhibitory effects on NADH oxidase and succinate dehydrogenase, whereas higher concentrations of ketoconazole were required to inhibit the activity of succinate dehydrogenase. N-deacetylated ketoconazole inhibited succinate dehydrogenase with an I₅₀ of 350 μM. In addition, the reduction of ferricyanide by succinate catalyzed by succinate dehydrogenase demonstrated that ketoconazole caused a dose-dependent inhibition of succinate activity (I₅₀ of 74 μM). In summary, ketoconazole appears to be the more potent mitochondrial inhibitor of the azoles studied; complex I of the respiratory chain is the apparent target of the drug's action. © 1997 John Wiley & Sons, Inc.     

Decrease in mitochondrial levels of adenine nucleotides and concomitant mitochondrial dysfunction in ischemic rat liver

The process of mitochondrial dysfunction in ischemic rat liver was studied. A close correlation was found between decrease in the mitochondrial adenine nucleotide content and deterioration of oxidative phosphorylation capacity. The level of total adenine nucleotides, which was 15--20 nmol/mg protein in mitochondria isolated from normal liver, fell to 1--2 nmol/mg protein with concomitant loss of oxidative phosphorylation capacity after anoxic incubation in vitro or in vivo for 120 min. However, neither the permeability barrier to adenine nucleotides nor matrix enzymes were affected under these conditions. The loss of adenine nucleotides was ascribed to degradation of AMP to adenosine and then leakage of the latter. Conventional procedures for maintenance of oxidative phosphorylation capacity of isolated mitochondria, preservation in the cold and addition of ATP or a respiratory substrate under aerobic conditions, were very effective in maintaining the intramitochondrial levels of adenine nucleotides. Of the three species of adenine nucleotides, only AMP was ineffective in maintaining mitochondrial function; mitochondria containing more than 5 nmol of ATP plus ADP/mg protein exhibited normal activity of oxidative phosphorylation, but with less than 2 nmol they showed no activity.     

全脑缺血预处理诱导大鼠海马缺血耐受的实验研究

目的和方法：采用大鼠四血管闭塞全脑缺血模型（4－vessel occlusion,4VO）及组织病理学方法,观察预缺血的持续时间,和预缺血与其后的损伤性缺血之间的间隔时间对海马缺血耐受形成的影响。结果：缺血6min即可导致海马组织明显的神经元延迟性死亡（delayed neuron death,DND),而缺血3min不足以引起海马组织明显的DND。经过3min缺血预处理,可对间隔1d和3d后6min缺血引起的大鼠海马DND产生明显的保护作用（P＜0．01）。但是,1min缺血预处理对间隔1d后6min缺血引起的DND不产生明显影响;5min缺血预处理时间隔1d后6min缺血,以及3min缺血预处理对间隔1h后6min缺血引起的DND不但没有保护作用,反而有使海马组织损伤累积加重的趋势。结论：在4VO大鼠模型中,全脑缺血预处理确能诱导海马对缺血性损伤产生耐受,诱导海马缺血耐受所需缺血预处理的适宜期间为3min左右,预缺血与后续损伤性缺血之间需要间隔足够的时间,适宜间隔在1－3d左右。     

大鼠肢体缺血预处理对肝缺血/再灌注损伤的保护作用

目的：研究肢体缺血预处理对大鼠肝缺血/再灌注损伤是否具有保护作用。方法：雄性SD大鼠32只,随机分为对照组（S组）;缺血/再灌注组（I/R组）;经典缺血预处理组（IPC组）;肢体缺血预处理组（远端缺血预处理组,RPC组）。S组仅行开腹,不作其他处理;IPC组以肝缺血5min作预处理;RPC组以双后肢缺血5min,反复3次作预处理,2个预处理组及I/R组均行肝缺血1h再灌注3h。取血用于血清谷丙转氨酶（ALT）与血清谷草转氨酶（AST）检测。切取肝组织用于测定湿干比（W/D）、中性粒细胞（PMN）计数及观察显微、超微结构的变化。结果：与I/R组比较,IPC组,RPC组ALT,AST,W/D值,及PMN计数均明显降低（P〈0.01）,肝脏的显微及超微结构损伤减轻。结论：肢体缺血预处理对大鼠肝脏I/R损伤有明显的保护作用,强度与经典缺血预处理相当,其机制可能与抑制肝脏炎症反应、减轻肝脏水肿、改善肝组织微循环有关。     

Ischemic preconditioning attenuates mitochondrial localization of PTEN induced by ischemia-reperfusion

Although the induction of myocyte apoptosis by ischemia-reperfusion (I/R) is attenuated by ischemic preconditioning (IPC), the underlying mechanism is not fully understood. Phosphatase and tensin homologs deleted on chromosome 10 (PTEN) promotes apoptosis through Akt-dependent and -independent mechanisms. We tested the hypothesis that IPC attenuates the mitochondrial localization of PTEN in the myocardium induced by I/R. Isolated hearts from wild-type mice were exposed to IPC or normal perfusion followed by 30 min of ischemia and reperfusion. IPC attenuated myocardial infarct size and apoptosis after I/R. Heart fractionation showed that mitochondrial PTEN and Bax protein levels and the physical association between them were increased by 30 min of I/R and that IPC attenuated all of these effects of I/R. Muscle-specific PTEN knockout decreased mitochondrial Bax protein levels in the reperfused myocardium and increased cell survival. To determine whether PTEN relocalization to mitochondria was influenced by I/R-induced production of ROS, hearts were perfused with N-acetylcysteine (NAC) to scavenge ROS or H(2)O(2) to mimic I/R-induced ROS. Mitochondrial PTEN protein levels were decreased by NAC and increased by H(2)O(2). PTEN protein overexpression was generated in mouse hearts by adenoviral gene transfer. PTEN overexpression increased mitochondrial PTEN and Bax protein levels and ROS production, whereas muscle-specific PTEN knockout produced the opposite effects. In conclusion, myocardial I/R causes PTEN localization to the mitochondria, related to the generation of ROS; IPC attenuates the mitochondrial localization of PTEN after I/R, potentially inhibiting the translocation of Bax to the mitochondria and resulting in improved cell viability.     

Effect of exhaustive exercise on liver mitochondrial function in the rat

The oxidative and phosphorylative function of rat liver mitochondria after exhaustive exercise was investigated. The stimulation of state 4 respiration (without ADP) with NADH and FADH2 dependent substrates was demonstrated. The reduction in RCR ratio (the rate of oxidation in state 3/the rate of oxidation in state 4) and enhanced activity of oligomycin sensitive ATP-ase was also found. The results suggest an inhibition of liver mitochondrial phosphorylative activity in rats exercised till exhaustion.     

Ischemic preconditioning is not additive to preservation with hypothermia or crystalloid cardioplegia in the globally ischemic rat heart

The aim of this study was to evaluate the additive protective efficiency of ischemic preconditioning when used in combination with conventional clinically relevant cardioprotective methods of hypothermia or hypothermic cardioplegia during sustained global ischemia.Isolated rat hearts were aorta-perfused with Krebs-Henseleit buffer and were divided into six groups (n = 10 each). Group I: Ischemia at 34°C for 60 min; Group PC+I: preconditioned (PC) ischemia at 34°C, 2 episodes of 5 min ischemia and 10 min reperfusion at 34°C followed by I; Group HI: hypothermic ischemia at 10°C for 60 min; Group PC+HI: preconditioned (PC) hypothermic ischemia, 2 episodes of 5 min ischemia and 10 min reperfusion at 34°C followed by HI; Group CPL+HI: single dose of 'Plegisol' cardioplegia followed by HI; Group PC+CPL+HI: preconditioned hypothermic cardioplegia, followed by CPL+HI. At the end of 60 min ischemia, all the hearts were reperfused at 34°C for 30 min when post-ischemic recovery in left ventricular contractile function and coronary vascular dynamics was computed and compared.There was a significant depression in the post-ischemic recovery of developed pressure (P_max), positive derivative of pressure (+dp/dt), negative derivative of pressure (-dp/dt) and heterometric autoregulation (HA) of contractile force in all the groups, with no major differences between the groups. Left ventricular end-diastolic pressure (LVEDP) was significantly elevated after I at 34°C. Preconditioning (PC+I) prevented the rise in the LVEDP and this was accompanied by a significant reduction in the release of purine metabolises in the coronary effluents, particularly adenosine, during the immediate reperfusion period. Hypothermia (HI) provided essentially the same level of metabolic and mechanical preservation as offered by PC+I. Combination of hypothermia with preconditioning (PC+HI) or cardioplegia (PC+CPL+HI), did not further enhance the preservation. Post-ischemic recovery in the regional contractile function (segment shortening, %SS) followed nearly identical pattern to global (P_max) recovery. Post-ischemic recovery in coronary flow (CF) was significantly reduced and coronary vascular resistance (CVR) was significantly increased in all the groups. Myogenic autoregulation (transient and sustained) was generally enhanced indicating increased vascular reactivity. Preconditioning did not alter the time-course of these changes.Preconditioned ischemia (34°C) preserved left ventricular diastolic functions and prevented the contracture development after sustained ischemia reperfusion at 34°C. This protective effect of preconditioning was possibly mediated by the reduction in the breakdown of purine metabolises. Hypothermia alone or in combination with crystalloid cardioplegia prevented the irreversibility of the ischemic injury but produced contractile and vascular stunning which was not improved by ischemic preconditioning. The results of this study indicate that preconditioning when combined with hypothermia or hypothermic cardioplegia offered no significant additional protection.     

p38 MAPK反义寡聚脱氧核苷酸阻断肢体缺血预处理诱导的脑缺血耐受

目的:观察p38MAPK反义寡聚脱氧核苷酸(As-ODN)对肢体缺血预处理(LIP)诱导的脑缺血耐受的影响。方法:48只永久凝闭双侧椎动脉的Wistar大鼠分为8组(n=6):sham组、LIP组、脑缺血损伤组、LIP+脑缺血损伤组、双蒸水+LIP+脑缺血损伤组、p38MAPKAs-ODN组和p38MAPKAs-ODN+LIP+脑缺血损伤组,p38MAPKAs-ODN的剂量又分为5nmol/5μl和10nmol/5μl。所有动物均在sham手术后或末次全脑缺血/再灌注后7天断头取脑,硫堇染色观察海马CA1区锥体神经元迟发性死亡情况。结果:sham组和LIP组均未见延迟性神经元死亡(DND)。与sham、LIP组相比,脑缺血损伤组出现了明显的DND,表现为组织学分级(HG)升高和锥体神经元密度(ND)下降(P0.05)。LIP可显著抑制脑缺血损伤引起的DND。与LIP+脑缺血损伤组相比,p38MAPKAs-ODN+LIP+脑缺血损伤组出现了显著的DND,表现为HG升高、ND降低(P0.05),且此种变化与p38MAPKAs-ODN的注射剂量呈明显正相关。结论:p38MAPKAs-ODN可阻断LIP诱导的脑缺血耐受,进一步证实了p38MAPK表达上调参与了LIP诱导的脑缺血耐受。     

Differential alterations in mitochondrial function induced by a choline-deficient diet: understanding fatty liver disease progression

Non-alcoholic fatty liver disease (NAFLD) is an increasingly reported pathology, characterized by fat accumulation within the hepatocyte. Growing evidences suggest specific effects on mitochondrial metabolism, but it is still unclear the relationship between fatty liver progression and mitochondrial function. In the present work we have investigated the impact of fatty liver on mitochondrial bioenergetic functions and susceptibility to mitochondrial permeability transition (MPT) induction in animals fed a choline-deficient diet (CDD) for 4, 8, 12 or 16 weeks. Mitochondria isolated from CDD animals always exhibited higher state 4 respiration. Mitochondrial membrane potential was decreased in CDD animals at 4 and 16 weeks. At 12 weeks, oxidative phosphorylation was more efficient in CDD animals, suggesting a possible early response trying to revert the deleterious effect of increased triglyceride storage in the liver. However, mitochondrial dysfunction was evident in CDD animals at 16 weeks as indicated by decreased RCR and ADP/O, with a corresponding decrease in respiratory chain enzymes activities. Such loss of respiratory efficiency was associated with accumulation of protein oxidation products, in tissue and mitochondrial fraction. Additionally, although no differences in ATPase activity, the lag phase was increased in mitochondria from CDD animals at 16 weeks, associated with decreased content of the adenine nucleotide translocator. Increased susceptibility to calcium-induced MPT was evident in CDD animals at all time points. These results suggest a dynamic mechanism for the development of NALFD associated with altered mitochondrial function.     

Improvement of rat liver function by energy repletion after the preservation period: implications for hepatic graft management

We very recently showed (using a blood-free perfusion model) that cold preservation sensitized rat hepatocyte functions to rewarming ischemic injury and that the injury can be prevented by repleting high-energy adenylates in the liver by short-term oxygenated warm reperfusion. Here we investigated whether short-term reperfusion after the preservation period can improve hepatic graft function in a blood reperfusion model. Eighteen-hour cold-preserved rat livers either untreated (Group A) or pretreated by 30-min oxygenated warm reperfusion after preservation (Group B) were subjected to 20-min ischemic rewarming and then reperfused with blood. Livers in Group B compared to Group A exhibited approx. three times increased bile production and bromosulfophthalein excretion, nearly 7-fold decreased swelling, and 1.2-fold improved blood flow. These results suggest that repletion of the energy by short-term oxygenated reperfusion after prolonged preservation may improve markedly initial hepatic graft function.     

Adenosine receptors in rat testes: labeling with 3H-cyclohexyladenosine

We have labeled adenosine receptors in rat tissues with ³HN⁶cyclohexyladenosine (³HCHA) and evaluated the organ distribution and drug specificity of these binding sites throughout the body. Detectable receptor concentrations are restricted to the brain and testes. Brain displays receptor levels of 9 pmoles/g wet weight of tissue while the testes display 2 pmoles/g, with all other tissues examined showing less than detectable specific binding of ³HCHA. The receptors in these two tissues appear to possess identical pharmacologic profiles with an A₁ specificity for both. No change in the total number of ³HCHA binding sites is seen in testes of rats which had been hypophysectomized 14 days prior to sacrifice. This may exclude the Leydig cells as a source of adenosine receptors in the rat testes.     

Adenosine aminohydrolase activity in the regenerating rat liver

The specific activity of adenosine aminohydrolase in the regenerating rat liver is significantly increased 12 h after partial hepatectomy. There is a twofold increase in enzyme activity at 48 h, after which the activity begins to decline. However, increased values still persist 7 days postsurgery. The enzyme is located mainly in the soluble supernatant (90-95%) of the cell. The purified enzyme from 48-h regenerating liver and control liver has similar kinetic properties (Km 54-58 microM for adenosine), similar molecular weights (30,000-35,000), and are equally inhibited by an irreversible transition-state analog and a reversible competitive inhibitor. It is concluded that adenosine aminohydrolase in regenerating liver is an integral component of a salvage pathway designed for the reutilization of nucleotides, and thus helps maintain a "growth state" for the regenerating liver.