The effects of allopurinol in hepatic ischemia and reperfusion: experimental study in rats

Garlic and allopurinol attenuate hepatic apoptosis induced by fipronil in male albino rats

Fipronil (FPN) can induce oxidative tissue damage and may be contemplated as an apoptosis inducer. Our aim is to investigate the possible hepatoprotective roles of garlic or allopurinol (ALP) against fipronil subacute toxicity. Thirty-six mature male albino rats were randomly divided into six groups; the first group was saved as control (C), the 2nd (G) was orally intubated with 500 mg/kg aqueous garlic extract, and the 3rd (A) received 150 mg/L allopurinol in their drinking water. The 4th group (F) was administered 13.277 mg/kg fipronil by gavage, while the 5th (G + F) and 6th (A + F) groups received the same doses of garlic and allopurinol, respectively two hours before fipronil intoxication. Our results revealed that FPN significantly increased the hepatic malondialdehyde, protein carbonyl levels, and the enzymatic activities of superoxide dismutase, catalase, glutathione peroxidase, and xanthine oxidase, but it decreased glutathione-S-transferase compared to the control group. Moreover, FPN exhibited significant up-regulation in the hepatic pro-apoptotic (Bax) and caspase-3 genes expression, down-regulation in the anti-apoptotic (Bcl-2) mRNA gene expression and induced DNA fragmentation. Surprisingly, garlic or allopurinol co-treatment ameliorated the hepatic lipid peroxidation, antioxidants disruption, and apoptosis induced by FPN. In conclusion, garlic and allopurinol relieved the oxidative injury and reduced the fipronil-induced apoptosis probably by improving the tissue antioxidant defense system.

Evaluation effects of allopurinol and FSH on reduction of ischemia-reperfusion injury and on preservation of follicle after heterotopic auto-transplantation of ovarian tissue in mouse

Purpose

Allopurinol and FSH injection are applied to reduce ischemia-reperfusion injury and to increase survival rate for ovarian follicles after ovarian heterotopic autotransplantation in mice.

Methods

Ovarian tissues from 6-week-old mice were grafted into back muscle then collected after 3 weeks. A total of five groups were included in this experiment as follows: control group (n = 5), sham-operated group (n = 5), allopurinol treatment group (AP) (n = 5), follicle stimulating hormone (FSH) treatment group (n = 5), as well as, allopurinol and FSH treatment group (APF) (n = 5). We investigated survival, number and development of follicles, vaginal cytology along with plasma malondialdehyde (MDA) concentration in grafted ovary.

Results

Total follicles count significantly increased in APF group compared with other treatment groups (p < 0.05). MDA concentration significantly decreased in AP group and APF treatment group compared with sham-operated group. In AP group, vaginal smears showed presence of cornified epithelial cells three-five day after surgery.

Conclusions

We demonstrated that allopurinol, as a XO inhibitor, plays an important role in order to decrease ischemia injury and to increase survival rate for follicles. Also, FSH, as a folliculogenesis and angiogenesis factor, increases development of follicles. It seems that allopurinol can cause re-establishing hypothalamus-pituitary axis and finally can restore estrous cycle earlier than for the sham operated group, so it explains the increasing survival rate for follicles.

Allopurinol and xanthine oxidase inhibition in liver ischemia reperfusion

INTRODUCTION

Allopurinol was first introduced, in 1963, as a xanthine oxidase inhibitor when it was investigated for concomitant use with cancer chemotherapy drugs. Today it is used in gout and hyperuricemia. Due to its additive benefit in preventing oxidative damage, attention has shifted towards the use of allopurinol in organ ischemia and reperfusion.

CURRENT STATUS

Currently, the mechanism by which allopurinol exerts a protective benefit in ischemia reperfusion related events is not fully understood. There are various theories: it may act by inhibiting the irreversible breakdown of purine substrates, and/or by inhibiting the formation of reactive oxygen species, and/or by protecting against damage to the mitochondrial membrane.

AIM

This work focuses on liver ischemia and reperfusion injury in an effort to better understand the mechanisms associated with allopurinol and with this pathological entity.

REVIEW OF LITERATURE

The current research, mainly in animal models, points to allopurinol having a protective benefit, particularly if used pre-ischemically in liver ischemia reperfusion injury. Furthermore, after reviewing allopurinol dosing and administration, it was found that 50 mg/kg is statistically the most effective dose in attenuating liver ischemia reperfusion injury. Owing to the limited number of samples, the time of administration did not show statistical difference, but allopurinol was often beneficial when given around 1 h before ischemia.

CONCLUSION

In conclusion, allopurinol, through its known xanthine oxidase inhibitory effect, as only one of the potential mechanisms, has demonstrated its potential application in protecting the liver during ischemia and reperfusion.

Tissue protective effect of xanthine oxidase inhibitor, polymer conjugate of (styrene–maleic acid copolymer) and (4-amino-6-hydroxypyrazolo[3,4-d]pyrimidine), on hepatic ischemia–reperfusion injury

The detrimental role of superoxide anion (O2−) has been well documented in the pathogenesis of ischemia–reperfusion (I/R) injury. Our and other studies suggested that one critical source of O2− generation may be xanthine oxidase (XO). We thus hypothesized that I/R injury could be protected by inhibiting XO activity, which would reduce the amount of O2− and hence reduce pathogenic consequences. Among various XO inhibitors, we previously found 4-amino-6-hydroxypyrazolo[3,4- d]pyrimidine (AHPP) exhibited potent XO inhibitory activity. Here, we report that the covalent conjugate of AHPP with amphipathic styrene–maleic acid copolymer (SMA-AHPP) showed protective effect against I/R-induced injury in a rat hepatic I/R model. Liver ischemia was induced by occluding both the portal vein and the hepatic artery for 30 min, and followed by reperfusion. SMA-AHPP was administered via the tail vein two hours before ischemia was initiated. A remarkable increase of liver enzymes in plasma (aspartate aminotransferase, AST; alanine aminotransferase, ALT and lactate dehydrogenase, LDH) was detected three hours after reperfusion, whereas prior injection of SMA-AHPP greatly suppressed this increase of AST, ALT and LDH. Moreover, induction of inflammatory cytokines, i.e. tumor necrosis factor-alpha (TNF- α), interleukin-12 (IL-12) and monocyte chemotactic protein-1 (MCP-1) by I/R were significantly inhibited by SMA-AHPP treatment. Accordingly, cytotoxic effect or apoptosis in the liver caused by I/R was clearly reduced by SMA-AHPP pretreatment. Furthermore, thiobarbituric acid-reactive substance assay showed a significant decrease of lipid peroxidation in rat liver after the administration of SMA-AHPP, which is parallel with the decreased XO activity after SMA-AHPP treatment, indicating the involvement of reactive oxygen species generated by XO. In addition, SMA-AHPP was found to bind to albumin, thus to exhibit prolonged in vivo (plasma) half-life. These results suggest that SMA-AHPP exerted a potent cytoprotective effect against I/R injury in rat liver, by inhibiting XO activity and the subsequent generation of O2−.

The Role of Antibiotic Prophylaxis With Sodium Ceftriaxone to Prevent Bacterial Translocation Associated With Hypovolemic Shock: An Experimental Study in Rats

One of the measures adopted to reduce or prevent intestinal bacterial translocation (BT) in patients who are in hemorrhagic shock consists of prophylactic antibiotics. This study attempted to assess the effectiveness of administering systemic antibiotic to suppress BT in rats submitted to hemorrhagic shock. Sixty-eight male Wistar rats were divided into two experiments. In experiment 1 (n = 28), the animals were randomly divided into three groups: group I (n = 7), sham operation; group II (n = 11), constituted by animals that were submitted to hemorrhagic shock by removing 40% of the volemia, and were resuscitated after 40 min of sustained shock, replacing the previously removed blood; and group III (n = 10), animals that, besides hemorrhagic shock and volemic replacement, received 50 mg/kg of sodium ceftriaxone intravenous 1 min after blood readministration. Mesenteric lymph nodes (MLN) for culture tests and segments of the small bowel were removed for histopathological studies 1 day after the operation in the three groups. In experiment 2, the same procedures were performed, except the laparotomy for removing MLN and segments of jejunal and ileal bowel, but the animals were followed during 7 days, in order to evaluate the mortality rate. In the control group (group I), the bacteriological assessment of the MLN was negative in all cases. Only 40% of the animals treated with antibiotics after hypovolemic shock (group III) presented positive bacteriological exams of the MLN, and this rate was 90% in the group of animals that did not receive this substance (group II) (p < .05). Escherichia coli was the bacteria identified most frequently in culture tests (92.8%). The villosities atrophy and inflammatory infiltrate of the lamina propria were the most common histological changes in the bowel, although the intensity was similar in groups II and III (p > .05), but more intense that in group I (p < .05). The mortality rates in groups I, II, and III 7 days after hypovolemic shock were 0%, 20%, and 20%, respectively. Prophylactic antibiotics significantly reduced the presence of bacteria in the MLN in situations of hypovolemic shock, in rats. This was probably related to a lower BT. However, this aspect did not modify the mortality rate of the animals. Also, the possibility that BT may not have a significant influence in this outcome should be considered.

Protective effects of apocynin and allopurinol on ischemia/reperfusion-induced liver injury in mice

AIM: To determine the effects of allopurinol, an inhibitor of xanthine oxidase, and apocynin, an inhibitor of NADPH oxidase, on oxidant stress and liver injury caused by hepatic ischemia/reperfusion (I/R) procedure in mice.

METHODS: Mice were pretreated with a xanthine oxidase inhibitor, allopurinol, or NADPH oxidase (NOX) inhibitor, apocynin before the hepatic I/R procedure. Then treated or untreated mice underwent the hepatic I/R procedure. The effects on hepatic injury and superoxide anions were determined after starting reperfusion.

RESULTS: A standard warm hepatic I/R procedure led to a marked increase in superoxide anion production as indicated by a superoxide anion tracer, MCLA. At the same time, the procedure caused profound acute liver injury, as indicated by elevated serum alanine aminotransferase and tumor necrosis factor-α levels, reduced liver glutathione levels and elevated malondialdehyde contents, as well as a high apoptotic cell count. All these changes were reversed by the use of apocynin or allopurinol prior to the hepatic I/R procedure.

CONCLUSION: Allopurinol and apocynin exerted protective effects on hepatic ischemia/reperfusion injury. The protection is associated with blocking the generation of superoxide anions during the hepatic I/R procedure by inhibiting xanthine oxidase and NADPH oxidase activity.

Alterations in the content of metal elements and fatty acids in hepatic ischaemia-reperfusion: induction of apoptotic and necrotic cell death

Ischaemia and reperfusion are related to oxidative stress, which alters with the redox-homeostasis of the liver cells. Our aim was to reveal the correlations between changes of metal element and fatty acid concentration (two main components of redox-balance) and apoptotic and necrotic processes of hepatic ischaemia-reperfusion. Wistar rats were divided into three groups: control, sham-operated and reperfusion. Hepatic ischaemia was induced for 45 min in the left lateral, left medial and right medial lobes followed by 24 h of reperfusion. Global redox parameters and glutathione peroxidase and superoxide dismutase activity were detected by luminometry and spectrophotometry. Routine laboratory measurements, fatty acid composition (with gas chromatography) as well as metal ion concentration of liver (with ICP-OES) were determined. Metallothionein activity was measured by atomic absorption spectrometry. Immunohistochemical and histological examinations were carried out to investigate apoptotic and necrotic changes in the liver. During reperfusion, global antioxidant parameters decreased and superoxide dismutase level of the liver was significantly lower than in the sham-operated group. Changes in the metal element concentration are essential for cellular biochemical pathways, and significant correlations were found between decrease in Cu and Zn content and decreased superoxide dismutase activity. Necrotic lesions along with increased number of apoptotic cells were found in the liver after 24 h of reperfusion. Alterations in the metal element and fatty acid content was found in the liver tissue during 24 h of ischaemia-reperfusion along with increase in the number of apoptotic cells and significant disturbance of the antioxidant balance. Study of the metal element content of the liver during hepatic ischaemia-reperfusion may provide new supportive strategies for liver surgery and transplantation.

Effect of antioxidant treatments on the gut-liver axis oxidative status and function in bile duct-ligated rats

BACKGROUND

Experimental and clinical studies have demonstrated the pivotal role of oxidative stress in the promotion of hepatic and intestinal injury in obstructive jaundice. The present study was undertaken to investigate the effect of well known antioxidant treatments on the gut-liver axis oxidative status and function in bile duct-ligated rats.

METHODS

A total of 60 male Wistar rats were randomly divided into six groups of 10 animals each: controls, sham operated, bile duct ligated (BDL), and BDL treated with either N-acetylcysteine (NAC), allopurinol, or alpha-tocopherol (alpha-TC). Ten days after treatment, the hepatic and intestinal oxidative status was estimated by measuring lipid peroxidation and a battery of biochemical markers comprising the organ's thiol redox state (i.e., glutathione, cysteine, protein thiols, oxidized glutathione, nonprotein mixed disulfides, oxidized cysteine derivatives, protein symmetrical disulfides, and protein mixed disulfides). Portal and aortic endotoxin concentrations and alanine aminotransferase (ALT) levels were also determined.

RESULTS

All antioxidant treatments significantly improved intestinal barrier function and protected from cholestatic liver injury, as evidenced by reduction of the portal and aortic endotoxin concentration and ALT levels, respectively. This effect accompanied their significant antioxidant action in both organs, mediated by a certain influence profile on the thiol redox state by each treatment.

CONCLUSION

NAC, allopurinol, and alpha-TC, exerting a potent combined antioxidant effect on the intestine and liver in experimental obstructive jaundice, significantly prevented intestinal barrier dysfunction and liver injury. The variety of results depending on the antioxidant agent that was administered and the marker of oxidative stress that was estimated, indicates that a battery of biomarkers would be more appropriate in assessing pharmacologic responses to therapeutic interventions.

Methimazole protects lungs during hepatic ischemia-reperfusion injury in rats: an effect not induced by hypothyroidism

BACKGROUND

Hepatic ischemia-reperfusion injury may lead to remote organ failure with mortal respiratory dysfunction. The aim of the present study was to analyze the possible protective effects of methimazole on lungs after hepatic ischemia-reperfusion injury.

METHODS

Forty male Wistar albino rats were randomized into five groups: a control group, in which bilateral pulmonary lobectomy was done; a hepatic ischemia-reperfusion group, in which bilateral pulmonary lobectomy was done after hepatic ischemia-reperfusion; a thyroidectomy-ischemia-reperfusion group (total thyroidectomy followed by, 7 days later, bilateral pulmonary lobectomy after hepatic ischemia-reperfusion); a methimazole-ischemia-reperfusion group (following methimazole administration for 7 days, bilateral pulmonary lobectomy was done after hepatic ischemia-reperfusion); and a methimazole +L-thyroxine-ischemia-reperfusion group (following methimazole and L-thyroxine administration for 7 days, bilateral pulmonary lobectomy was performed after hepatic ischemia-reperfusion). Pulmonary tissue specimens were evaluated histopathologically and for myeloperoxidase and malondialdehyde levels.

RESULTS

All of the ischemia-reperfusion intervention groups had higher pulmonary injury scoring indices than the control group (P < 0.001). Pulmonary injury index of the ischemia-reperfusion group was higher than that of both the methimazole-supplemented hypothyroid and euthyroid groups (P = 0028; P = 0,038, respectively) and was similar to that of the thyroidectomized group. Pulmonary tissue myeloperoxidase and malondialdehyde levels in the ischemia-reperfusion group were similar with that in the thyroidectomized rats but were significantly higher than that in the control, and both the methimazole-supplemented hypothyroid and euthyroid groups.

CONCLUSION

Methimazole exerts a protective role on lungs during hepatic ischemia-reperfusion injury, which can be attributed to its anti-inflammatory and anti-oxidant effects rather than hypothyroidism alone.

Evaluation of preservation solutions by ESR-spectroscopy: superior effects of University of Wisconsin over Histidine-Tryptophan-Ketoglutarate in reducing renal reactive oxygen species

Despite the causative role of oxidative stress in renal ischemia-reperfusion (I-R) injury effects of preservation solutions on reactive oxygen species (ROS) release have not been sufficiently evaluated. We compared the effects of most common solutions in kidney transplantation, University of Wisconsin (UW) and Histidine-Tryptophan-Ketoglutarate (HTK). ROS formation in isolated perfused rat kidney was detected by electron spin resonance spectroscopy using spin label 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine. Donor kidneys from Lewis rats were pretreated with saline (controls), in therapeutic groups, kidneys underwent 18 h of cold storage (CS) preserved by HTK or UW solution. Experimental protocol included a stabilization period followed by additional I-R. Kidneys preserved by HTK produced highest ROS values in the control period after CS, whereas levels in UW and control group did not vary significantly. A peak release induced by additional I-R was also significantly highest in HTK kidneys, and UW did not differ from controls. During reperfusion, levels in HTK exceeded control and UW values. Renal vascular resistance, caspase-3-activity, and tissue hydration were enhanced in HTK compared with UW group, whereas ATP concentration was less reduced in UW-preserved tissue. These data show the greater antioxidative potential of UW solution, which also attenuated organ impairment after CS in the early reperfusion period.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

Reduced antioxidant level and increased oxidative damage in intact liver lobes during ischaemia-reperfusion

AIM: To determine whether increased blood flow of the liver can cause oxidative stress and hepatocyte damage, and to elaborate methods suitable for measuring the antioxidant defence during hepatic surgery on rat model.

METHODS: In nembutal narcosis, the left lateral and the medial lobes of the liver were clipped for 45 min to make the total blood supply flow through the other lobes. Total antioxidant status, glutathione peroxidase and superoxide dysmutase activity, as well as the concentrations of diene conjugates and free sulphydril groups, H-donating ability and reducing power of the liver samples were determined. Chemiluminescent intensity of the liver was also measured. Metal ions (Al, Ca, Cu, Fe, Mg, Mn, Zn) and P and S concentrations of the liver were determined with an inductively coupled plasma optical emission spectrometer and Se content was measured by cathodic stripping voltammetry.

RESULTS: Glutathione peroxidase and superoxide dysmutase activities of the liver decreased significantly in the hyperemia group compared to those observed in the sham operated group. The level of total antioxidant status was also significantly lower in the hyperemia group. H-donating ability, reducing power and free sulphydril group concentration showed the same tendency. A significant correlation (P<0.05) was found between the changes in non-specific antioxidant activities. This pointed to simultaneous activity of the antioxidant defence system. Al, Cu, Mn, Zn, and S were lower in the hyperemia group than in the sham operated group when the levels of Ca, Fe, Mg, Se and P ions were higher during hyperemia.

CONCLUSION: Oxidative stress is one of the main factors for the injury of intact liver lobes during ischaemia-reperfusion.

Allopurinol provides long-term protection for experimentally induced testicular torsion in a rabbit model

OBJECTIVE

To assess the effect of five antioxidants on exocrine function of rabbit testes retained in situ for 24 h and 3 months after experimental torsion.

MATERIALS AND METHODS

The left testes of peripubertal rabbits were clamped for 60 min, after which the clamps were removed and the testes allowed to reperfuse. The right testes served as internal controls. There were eight rabbits in each of the following experimental groups: (a) sham; (b) 60-min ischaemia followed by reperfusion; (c) 60-min ischaemia followed by left orchidectomy. In five further groups, rabbits were exposed to 60-min ischaemia followed by reperfusion, but received one of the following antioxidants before reperfusion: acetyl salicylic acid, ascorbic acid, allopurinol, quercetin or superoxide dismutase. Both testes were excised at 24 h or 3 months. The degree of lipid peroxidation, a measure of free radical damage, was assessed in testicular tissue homogenates by measuring the tissue levels of malondialdehyde (MDA). The Johnsen score was used to assess the morphological damage at 24 h and 3 months for each group.

RESULTS

At 3 months twisted viable testes allowed to reperfuse had higher MDA levels than controls; the left testes of rabbits treated with allopurinol had significantly lower MDA levels than untreated rabbits and rabbits given other antioxidants. Rabbits given quercetin, ascorbic acid or superoxide dismutase had lower (but not significantly) left testicular MDA levels than untreated rabbits, while rabbits given acetyl salicylic acid had even higher levels. Allopurinol-treated rabbits had a Johnsen score of > 7.6 and those given other antioxidants had scores of < 7.6 at 3 months.

CONCLUSION

The twisted viable testis treated by orchidopexy contains high free radical levels at 3 months. Of the antioxidants studied, only allopurinol had a beneficial long-term effect, by significantly reducing testicular MDA levels at 3 months.

Effects of the free radical scavenger dimethyl sulphoxide on experimental normothermic ischaemia of the liver

BACKGROUND/AIMS

This study assessed the effects of intermittent or continuous hepatic ischaemia and reperfusion with or without dimethyl sulphoxide (DMSO) pre-treatment in a rat ischaemic model.

METHODS

One hundred and eighty rats were divided into three groups undergoing hepatic ischaemia of a total duration of 60, 90 and 120 min. Each group of rats was subdivided to receive either a continuous Pringle manoeuvre or intermittent liver pedicle clamping of 30 or 15 min. Ten minutes before ischaemia induction, 10 rats from each group were pre-treated with DMSO (500 mg/kg, b.w.) intravenously.

RESULTS

With continuous hepatic pedicle clamping, survival rates inversely correlated with the duration of ischaemia, with greater survival in the intermittently clamped groups (p < 0.05). DMSO pre-treatment did not affect survival but resulted in a significant reduction in liver enzyme (aspartate aminotransferase, alanine aminotransferase) release on the first postoperative day following total ischaemic times of 90 min or greater (p < 0.05). After 120 min of total ischaemia, DMSO pre-treatment resulted in higher preservation of adenosine 5'-triphosphate liver content (p < 0.05).

CONCLUSION

DMSO may be used to prolong tolerance to inflow occlusion and to limit the adverse effects of ischaemia and reperfusion cycles in an experimental hepatic ischaemia model.

Gadolinium chloride and salvia miltiorrhiza compound ameliorate reperfusion injury in hepatocellular mitochondria

AIM: To investigate the effect of gadolinium chloride (GaCl₃) and salvia miltiorrhiza compound (SMCo) on ischemia and reperfusion (I/R) injury in hepatocellular mitochondria.

METHODS: Wistar rats were randomly to divided into control group, GaCl₃ group, SMCo group and GaCl₃ + SMCo group (n = 15 each). GaCl₃ (7 mg·kg^-1) was injected into tail vein on d 1 and d 2 in contrast group. SMCo (2 mL·kg^-1) was injected into muscle on d 1 and d 2 in SMCo group. GaCl₃ + SMCo group received both GaCl₃ (iv) and SMCo (im) injection. Control group received saline injection only. On d 3, all the rats were subjected to 2 h ischemia in the middle and left lobes of the liver, followed by reperfusion for 2 h, 6 h and 18 h respectively. The level of serum alanine aminotransferase (ALT) and malondialdehyde (MDA) in hepatocellular mitochondria was measured. Pathological changes in hepatic tissue and in hepatocellular mitochondria were determined with optical microscope and electronic microscope, respectively.

RESULTS: Remarkablly pathohistological and biochemical changes were detected after 6 h of I/R. Compared with control, the level of ALT was decreased in GaCl₃, SMCo and GaCl₃ + SMCo treated groups (1314.0 ± 278.7 vs 809.4 ± 196.1, 716.6 ± 242.8 and 837.2 ± 190.6 IU·L^-1, respectively. P < 0.05). Similarly, the level of MDA was decreased in GaCl₃, SMCo and GaCl₃ + SMCo treated groups (293.1 ± 51.1 vs 190.8 ± 55.5, 214.3 ± 32.9 and 221.0 ± 47.3 nmol·g^-1, respectively, P < 0.05). Accordingly, in control group, swelling, degeneration, focal necrosis, infiltration of leucocyte were found in reperfused tissue under an optical microscope, and mitochondria swelling, rupture and even breakdown were seen under an electronic microscope. These pathohistological and ultrastructural damages caused by I/R were greatly attenuated in GaCl₃, SMCo and GaCl₃ + SMCo treated groups. However, there was no additive effect observed when GaCl₃ and SMCo were used together.

CONCLUSION: Both GaCl₃ and SMCo can alleviate the I/R injury in hepatocellular mitochondria.

Thyroxine prevents reoxygenation injury in isolated proximal tubule cells

Ischemia is characterized by cessation of blood flow and oxygen delivery to tissues that results in disruption of cellular structure and organelles. However, restoration of blood flow following ischemia causes reperfusion injury, characterized by further damage in the tissues mediated by reactive oxygen species. In the kidney, reactive oxygen molecules have been implicated in ischemic, toxic and immunological glomerular damage. Thyroxine has been shown to be cytoprotective in toxic and ischemic injury. Thyroxine's cytoprotective effect is postulated to be secondary to stimulation of intracellular ATP synthesis. However, the underlying mechanism of that beneficial effect remains to be investigated. In this study we investigated the effect of thyroxine (T4) on free oxygen radical production in an in vitro model of reperfusion injury. Free oxygen radical (FOR) levels were determined by a chemiluminescence method after freshly isolated rabbit proximal tubule cells were subjected to 15 min of anoxia followed by 45 min of reoxygenation. Reoxygenation injury resulted in a significant increase in FOR levels (P<0.0001). FOR levels were significantly lower in the group treated with thyroxine (P=0.01) and cells treated with thyroxine displayed better preservation of cellular structure. We conclude that thyroxine's cytoprotective effect might be via decreased synthesis of FOR, and thyroxine treatment may confer cytoprotection in renal conditions characterized by FOR-mediated injury.