Targeting of parasite-specific immunoliposome-encapsulated doxorubicin in the treatment of experimental visceral leishmaniasis

A parasite-specific 51-kDa protein has been isolated from the membrane of macrophages infected with Leishmania donovani, the causative agent of visceral leishmaniasis. Active targeting of doxorubicin to infected macrophages was studied by incorporating it in immunoliposomes prepared by grafting F(ab)'(2) of anti-51-kDa antibody onto the liposomal surface. In a 45-day mouse model of visceral leishmaniasis, complete elimination of spleen parasite burden was achieved by doxorubicin incorporated in immunoliposome (immunodoxosome) at a dose of 250 microg/kg/day that was given for 4 consecutive days. A similar dose of free and liposomal drug (doxosome) had 45% and 84% parasite suppressive effects, respectively. Immunodoxosome and doxosome were generally less toxic than the free drug, as determined by several clinical parameters of cardiotoxicity and liver toxicity. These results not only indicate the potential of doxorubicin as an effective chemotherapeutic agent but also establish the use of immunoliposomes as drug carrier in the therapy of leishmaniasis.     

Patterns in the distribution of visceral leishmaniasis in Transcaucasia

The paper considers the regularities of the spreading of visceral leishmaniasis (VL) and present state of its foci in the Transcaucasia, where sporadic cases of the disease occur now in some regions of the Georgian and Azerbaijan SSRs, which is associated with the natural foci. The number of Phlebotomus kandelakii, Ph. transcaucasicus, Ph. balcanicus, Ph. brevis--the most probable vectors of the VL causative agents--is still rather high at the foot of the Great Caucasus, in the Ararat valley, in some regions of the Georgian SSR to the south of Tbilisi and some other regions with natural foci of the VL causative agent. The established regularities are reflected on the map, comparing the landscape-determined mosquitoes accumulation sites with VL distribution among human population at the peak of the disease. The public health system should pay special attention to the areas of distribution of mosquitoes throughout the entire natural foci area with respect to visceral leishmaniasis.     

Recommendations for treating leishmaniasis with sodium stibogluconate (Pentostam) and review of pertinent clinical studies.

Pentavalent antimonial compounds have been the mainstay of the treatment of visceral, cutaneous, and mucosal leishmaniasis for approximately half a century. Pentostam (sodium stibogluconate) is the pentavalent antimonial compound available in the United States (through the Centers for Disease Control). As dosage regimens for treating leishmaniasis have evolved, the daily dose of antimony and the duration of therapy have been progressively increased to combat unresponsiveness to therapy. In the 1980s, the use of 20 mg/kg/day (instead of 10 mg/kg/day) of antimony was recommended, but only to a maximum daily dose of 850 mg. The authors have concluded on the basis of recent efficacy and toxicity data that this 850-mg restriction should be removed; the evidence to date, which is summarized here, suggests that a regimen of 20 mg/kg/day of pentavalent antimony, without an upper limit on the daily dose, is more efficacious and is not substantially more toxic than regimens with lower daily doses. We recommend treating all forms of leishmaniasis with a full 20 mg/kg/day of pentavalent antimony. We treat cutaneous leishmaniasis for 20 days and visceral and mucosal leishmaniasis for 28 days. Our judgment of cure is based on clinical criteria.     

Advances in the treatment of leishmaniasis

PURPOSE OF REVIEW: Treatment of leishmaniasis is far from satisfactory: all antileishmanial drugs are toxic and most have to be used parenterally for prolonged periods, especially for visceral leishmaniasis. In recent years, there has been a steady erosion in the efficacy of pentavalent antimony to cure visceral leishmaniasis in Bihar, India. In addition, several new antileishmanial formulations have become available. RECENT FINDINGS: Through the publication of three studies from Africa, generic sodium stibogluconate, which is a fraction of the price of the branded drug Pentostam, has proven to be equivalent to Pentostam both in terms of safety and efficacy. The first oral drug, miltefosine, has been approved for treating visceral leishmaniasis in India, and preliminary reports of its efficacy against cutaneous leishmaniasis have been published. Interesting studies on successful low/single dose treatment of Indian visceral leishmaniasis with liposomal amphotericin B have been published. Several trials using different approaches towards treating cutaneous leishmaniasis are also reviewed. The results of clinical trials of two oral compounds are reported - fluconazole in treating cutaneous leishmaniasis was found to be safe and effective, whereas sitamaquine (WR6026) for visceral leishmaniasis was found to be toxic with poor efficacy. SUMMARY: Generic stibogluconate enables the cost effective treatment of all forms of leishmaniasis as it remains the most important antileishmanial drug in most parts of the world. In India, successful single dose AmBisome for visceral leishmaniasis makes therapy simple and enables mass treatment, provided the drug cost is brought down. For cutaneous leishmaniasis, two new oral drugs, fluconazole and miltefosine, provide wider options to the clinician.     

SLC11A1 polymorphisms and susceptibility to visceral leishmaniasis in Moroccan patients

Human visceral leishmaniasis is endemic in the Mediterranean basin. Since most infections are sub-clinical or asymptomatic, host genetics can provide concrete evidence in determining disease outcome. SLC11A1/NRAMP1 is a candidate gene that may be related to host susceptibility versus resistance to intracellular pathogens. This study aimed to determine possible association of SLC11A1 polymorphisms with visceral leishmaniasis among Moroccan children. A total of 106 children who developed visceral leishmaniasis due to Leishmania infantum were enrolled in this study. The control group was composed of 137 unrelated children, 97 asymptomatic subjects (DTH+) and 42 healthy individuals (DTH) who had no evidence of present or past infection. Four polymorphisms were studied by PCR–RFLP and sequencing: (GT)n microsatellite in the 5′ exon 1; silent substitutions 469 + 14G/C in intron 4; amino acid substitution D543N in exon 15 and 823C/T polymorphism in exon 8. Thereafter, the frequencies of genotypes, alleles and haplotypes were estimated. Two polymorphisms were each significantly associated in the genotypes with visceral leishmaniasis: 823C/T in exon 8 and D543N in exon 15 when comparing visceral leishmaniasis and DTH+ groups. The results of haplotype frequencies suggested an evidence of association with resistance to visceral leishmaniasis for the “286GTG” and “288GCA” haplotypes, whereas, the “286GCG” haplotype appears to increase the risk to visceral leishmaniasis susceptibility.Our data provide insights into the possible role of SLC11A1 variation in visceral leishmaniasis susceptibility. These results must be regarded as preliminary but suggestive that further study with larger populations is worthwhile.     

Reduced lipid peroxidation in dilated hearts of cardiomyopathic turkeys

Adverse pulmonary reactions to some nitrofuran antibiotics are thought, in part, to involve production of reactive oxygen radicals. Furazolidone, a nitrofuran antibiotic, causes a dilated cardiomyopathy in domestic turkeys. The mechanism of this drug induced cardiomyopathy is unknown. We investigated the possible role of free radical injury in this heart failure model. Left ventricular lipid peroxidation capacity, assessed by two methods (the thiobarbituric acid reactive substances and lipid hydroperoxides assays respectively), was investigated in five 5-8 week old cardiomyopathic turkeys with severe cardiac dilatation, left ventricular dysfunction and systemic hypotension, and in five control birds. Superoxide dismutase activity, total and manganese, was also measured in the crude left ventricular homogenates. Both lipid peroxidation products were reduced in the myopathic hearts: thiobarbituric acid reactive substances (malondialdehyde) 70(SEM 4) v 86(3) nmol.100 mg protein-1 in controls, p less than 0.02; and lipid hydroperoxides 29(7) v 74(14) nmol.100 mg protein-1, p less than 0.02. Total superoxide dismutase activity was similar in cardiomyopathic and control hearts: 670(26) v 657(105) nitrite units.100 mg protein-1. Although total superoxide dismutase activity was unchanged, we found decreased manganese superoxide dismutase in the dilated hearts compared with controls (54% v 84% of total activity, p less than 0.02). In separate in vitro experiments furazolidone (2-10 mg.g wet weight-1) did not increase malondialdehyde production in turkey (or rat) left ventricular homogenates. These results indicate that cardiomyopathy induced by furazolidone is associated with decreased myocardial lipid peroxidation. Although as yet unexplained, the decrease may be due to a diminished amount of heart lipid susceptible to peroxidation accompanying the process of cardiac hypertrophy and dilatation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Visceral leishmaniasis in Ordubad District, Nakhichevan ASSR

Visceral leishmaniasis (VL) focus in the Ordubad District of the Nakhichevan ASSR has become active for the last years. Complex study of the focus, performed in 1985-1987, allowed to establish the following: VL causative agent, circulating in the Ordubad District belongs to the Leishmania infantum species. It was identified by isoenzymatic analysis (for 12 enzymes) and the Adler serological test. Disease cases prevailed in the upper part of the town of Ordubad and were confined to a small area (4 adjoining streets). Little children (up to 2 years old) prevail among patients. Spatial distribution of the disease correlated with indirect EIA data on healthy urban population (3116 persons examined) and stray dogs (152 animals examined). Mean percentage of positive assay results for the titers ranging from 1:80 to 1:20 was 8.0, for human population of Ordubad, and 19.1 for the dogs. Ten Phlebotominae species were found in Ordubad and its suburbs: Phlebotomus (Laroussius) major, Ph. (L.) kandelakii, Ph. (Adlerius) halepensis, Ph. (A.) balcanicus, Ph. (Phlebotomus) papatasi, Ph. (Paraphlebotomus) sergentii, Ph. (Par.) caucasicus, Ph. (Par.) alexandri, Sergentomyia dentata, S. palestinensis. Authors suggest that stray dogs are reservoirs of infectious agents in the Ordubad focus, while Phlebotominae of the Laroussius and Adlerius subspecies are disease carriers, the disease being regarded as a Mediterranean form of visceral leishmaniasis.     

Chemotherapy for leishmaniasis: biochemical mechanisms, clinical efficacy, and future strategies

The 1980s have seen significant advances in the treatment of cutaneous, mucosal, and visceral leishmaniasis. Safe regimens of pentavalent antimony in the form of Pentostam (Wellcome Foundation, London; 20 mg of antimony/[kg.d] for 20-30 days) have produced initial cure rates of greater than 90% in these diseases. Biochemical investigations have demonstrated at least three parasite-specific features relevant to the mechanism of action of chemotherapeutic agents: (1) Organization of glycolytic enzymes and some enzymes of fatty acid catabolism into organelles (glycosomes) occurs in Leishmania but not in mammalian cells. Since antimony inhibits both amastigote catabolism of glucose via glycolytic enzymes and catabolism of fatty acids, the mechanism of action of antimony may relate to alteration of glycosomal structure or function. (2) Purine analogues can be utilized by the salvage pathway of purine biosynthesis in amastigotes to a greater extent than in mammalian cells, and allopurinol and allopurinol ribonucleoside are metabolized into presumably toxic nucleotides by these means. (3) Amastigote sterol biosynthesis is akin to that of such fungi as Candida in that the major demethylated sterol is of the ergostane series and in that ketoconazole inhibits its synthesis. Preliminary clinical studies suggest that the purines and the sterol inhibitors may have clinical utility as oral agents against cutaneous leishmaniasis. Possible treatment strategies for the classic and experimental agents have been proposed.     

Superoxide dismutase activity in children with chronic liver diseases

BACKGROUND/AIMS: Liver disease in infancy has multiple etiologies. As reactive oxygen intermediates are involved in several types of tissue damage, we have investigated whether different forms of liver disease in infancy are associated with increased free radical generation, using an indirect approach in which superoxide dismutase (a free radical scavenger) activity is determined in the liver tissue. METHODS: A total of 48 liver biopsies performed at diagnosis were evaluated retrospectively. Nine infants had biliary atresia, eight Alagille syndrome, seven alantitrypsin deficiency and 12 cryptogenic hepatitis. As controls we studied 12 biopsies with normal histology obtained from seven children with portal vein thrombosis and five children who underwent biopsy for management reason but had no liver disease. Superoxide dismutase activity in liver biopsy specimens was measured using the cytochrome C method by spectrophotometry and expressed as U SOD/mg protein. RESULTS: Superoxide dismutase activity was significantly increased in biliary atresia (1.25 +/- 0.56 U SOD/mg protein, p<0.0001) and Alagille syndrome (1.31 +/- 0.56 U SOD/mg protein, p<0.0001) as compared with al-antitrypsin deficiency (0.75 +/- 0.3 U SOD/mg protein), neonatal hepatitis (0.72 +/- 0.37 U. SOD/mg protein) and normal controls (0.4 +/- 0.7 U. SOD/mg protein). The highest level of SOD activity was found, however, in control children with portal vein thrombosis (2.09 +/- 0.96 U SOD/mg protein; p<0.0001 as compared to the other groups). CONCLUSION: Superoxide dismutase, a key enzyme in free radical protection, is increased significantly in the liver tissue of infants with cholestatic liver disease due to bile duct damage and in children with portal vein thrombosis, suggesting that products of free radical reactions are involved in the pathogenesis of these disorders.     

New insights about cross-reactive epitopes of six trypanosomatid genera revealed that Crithidia and Leptomonas have antigenic similarity to L. (L.) chagasi

We investigated whether ELISA using crude antigens from insect and plant trypanosomatids, which are non-pathogenic and easily cultivated in large scale, has the same positivity data as Leishmania (Leishmania) chagasi, the etiological agent of human visceral leishmaniasis (VL) or canine leishmaniasis (CanL), or as Trypanosoma cruzi, the etiological agent of Chagas disease (CD). The antigens from Crithidia fasciculata, Crithidia luciliae, and Leptomonas seymouri showed 100% cross-reactivity with VL and CanL samples, with no statistically titers differences from L. (L.) chagasi, however, 34% (17/50) of VL samples revealed higher titers using the insect trypanosomatids than the homologous antigen. On the other hand, antigens from Strigomonas culicis, Angomonas deanei, and Phytomonas serpens showed low cross-reactivity with VL and CanL samples. The sera from patients with American tegumentary leishmaniasis showed low levels of cross-reactivity with all trypanosomatids investigated, even with L. (L) chagasi, without titers dissimilarity among them. These parasites were also worthless as antigen source for detection of CD cases, which required homologous antigens to reach 100% positivity. This study showed, by ELISA, that crude extract of Crithidia and Leptomonas have epitopes similar to L. (L.) chagasi, which supports the idea of using them as antigens source for the serodiagnosis of visceral leishmaniasis.     

Visceral leishmaniasis unresponsive to pentostam caused by Leishmania tropica in Kenya

We report the characterization of 6 Leishmania tropica isolates from 2 patients with visceral leishmaniasis who were unresponsive to treatment with sodium stibogluconate. The Leishmania isolates, MHOM/KE/81/NLB-029A, -029XIB, and -029XIC and MHOM/KE/81/NLB-030I, -030B, and -030XXA, all from splenic aspirates, were characterized by cellulose acetate electrophoresis using 11 enzymes: malate dehydrogenase, malic enzyme, phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, superoxide dismutase, glutamate-oxaloacetate transaminase, adenylate kinase, nucleoside hydrolase, mannose phosphate isomerase, glucose phosphate isomerase, and phosphoglucomutase. Isozyme migration patterns were indistinguishable from those of 2 WHO reference strains of Leishmania tropica (MHOM/SU/60/LRC-L39, NLB-305 and MHOM/IQ/OO/LRC-L36, NLB-067). These are the first reported cases of visceral leishmaniasis (kala-azar) caused by L. tropica in Africa; these cases were refractory to sodium stibogluconate.     

Blood meal identification and parasite detection in laboratory-fed and field-captured Lutzomyia longipalpis by PCR using FTA databasing paper

The phlebotomine sand fly Lutzomyia longipalpis takes blood from a variety of wild and domestic animals and transmits Leishmania (Leishmania) infantum chagasi, etiological agent of American visceral leishmaniasis. Blood meal identification in sand flies has depended largely on serological methods but a new protocol described here uses filter-based technology to stabilise and store blood meal DNA, allowing subsequent PCR identification of blood meal sources, as well as parasite detection, in blood-fed sand flies. This technique revealed that 53.6% of field-collected sand flies captured in the back yards of houses in Teresina (Brazil) had fed on chickens. The potential applications of this technique in epidemiological studies and strategic planning for leishmaniasis control programmes are discussed.     

Chemotherapy of leishmaniasis: recent advances in the treatment of visceral disease

New lipid formulations of amphotericin B--AmBisome, Amphotec, and Abelcet--have dramatically decreased the toxicity associated with amphotericin B and have made this group of agents the treatment of choice for visceral leishmaniasis. An agent of a completely different chemical class, the aminoglycoside aminosidine, was 97% curative in India. This agent too may be used for visceral leishmaniasis.     

Interleukin 10 receptor blockade--pentavalent antimony treatment in experimental visceral leishmaniasis

Interleukin 10 (IL-10), a suppressive Th2 cell-type cytokine, promotes disease progression in experimental visceral leishmaniasis. To extend testing the therapeutic effects of applying IL-10 receptor (IL-10R) blockade with antileishmanial chemotherapy, BALB/c mice with established intracellular Leishmania donovani infection were injected once with anti-IL-10R mAb at the time low-dose, daily pentavalent antimony (Sb) therapy was initiated. In this treatment model, simultaneous administration of anti-IL-10R enhanced overall antileishmanial activity in the liver in an interferon-gamma-dependent fashion, and accelerated the kinetics of Sb-associated killing, induced a >10-fold Sb dose-sparing effect and shortened the required duration of Sb treatment. These results suggest the possibility of using mAb-induced IL-10R blockade to develop low-dose and/or short-course immunochemotherapeutic regimens in visceral leishmaniasis.     

Excreted factors and membrane-associated carbohydrates of Indian leishmaniae

Antigenic identity between the cell surface carbohydrate ligands and their excreted factor (EF) in all forms of Indian leishmaniasis were assessed by 11 carbohydrate-specific lectins. Our results demonstrated that 3 lectins, viz. PNA, SBA and WFA showed unique selectivity towards skin-dwelling parasites. The EFs of visceral leishmaniasis (VL), post-kala-azar dermal leishmaniasis (PKDL) and cutaneous leishmaniasis (CL) formed band against ConA at 1000, and 500 micrograms/ml concentration, respectively. RCA-120 at 3 mg/ml concentration was positive to both Leishmania tropica and L. major, whereas SBA was specific to L. tropica, L. major and PKDL strains at the same concentration. Antisera directed against the EFs (EF-As) induced agglutination to homologous promastigotes suspension. Cross-reactivity of agglutination was observed in different strains but highest was found among PKDL and CL strains. Although PKDL cases are normally found in patients with the history of visceral leishmaniasis (kala-azar), surprisingly in this study, the surface saccharides of PKDL strains had close affinity to CL type instead of VL.     

Superoxide mediates the toxicity of paraquat for Chinese hamster ovary cells.

The roles of superoxide and H2O2 in the cytotoxicity of paraquat were assessed in Chinese hamster ovary cells. Neither catalase nor superoxide dismutase inhibited the loss of ability to form colonies when added to the medium. When introduced into the cells, superoxide dismutase but not catalase inhibited the toxicity of paraquat. That superoxide dismutase acted by its known catalytic action is shown by the loss of inhibition when the enzyme was inactivated by H2O2 before being introduced into the cells. The lack of inhibition by catalase, by dimethyl sulfoxide, and by desferoxamine suggests that the toxicity is not mediated by a reaction between H2O2 and superoxide to engender the hydroxyl radical. Exposure of Chinese hamster ovary cells to paraquat may be a suitable means to determine the effects of superoxide anion in cultured cells and the ways in which cells can resist this toxic action.     

Treatment of Helicobacter pylori infection favourably affects gastric mucosal superoxide dismutases.

BACKGROUND AND AIMS: Excessive production of reactive oxygen metabolites (ROMs) by phagocytic cells is thought to contribute to the mucosal pathology of Helicobacter pylori infection. Previously, H pylori infection was shown to have a differential effect on some gastric mucosal scavenger enzymes of ROMs-namely, mitochondrial and cytoplasmic superoxide dismutases-reflected by a large increase in the cytokine inducible manganese superoxide dismutase and a marginal decrease in the constitutive copper/zinc superoxide dismutase. The present study was performed to evaluate whether these altered mucosal superoxide dismutase concentrations and activities in H pylori associated gastritis are reversed to normal by successful treatment of the infection. PATIENTS AND METHODS: In two different treatment groups-namely, omeprazole or ranitidine, in combination with clarithromycin and metronidazole (OME/AB (n = 33) and RAN/AB (n = 30))-manganese superoxide dismutase and copper/zinc superoxide dismutase concentrations were evaluated by enzyme linked immunosorbent assays in homogenates of gastric antrum and corpus biopsy specimens obtained before and eight weeks after successful treatment of H pylori infection. Superoxide dismutase activities in these homogenates were determined spectrophotometrically in eight patients of both groups before and after successful treatment. The concentrations of gastric mucosal superoxide dismutases were also determined in 12 patients with a persistent H pylori infection, with (n = 4) or without (n = 8) eradication therapy. Infection and eradication of H pylori were confirmed by a combination of culture and histology. RESULTS: Concentrations of manganese superoxide dismutase were significantly lower after than before therapy in antral (p < 0.001 in both treatment groups) and corpus (p < 0.001 in both treatment groups) mucosa. By contrast, copper/zinc superoxide dismutase concentrations were significantly higher (p < 0.001) only in antral mucosa of the OME/AB treated group. Manganese superoxide dismutase activity was significantly lower after than before treatment in antral (OME/AB p < 0.01, RAN/AB p < 0.001), but not in corpus mucosa. Copper/zinc superoxide dismutase activity was not significantly altered by therapy. In the 12 patients with a persistent H pylori infection no major changes in the gastric mucosal superoxide dismutase concentrations were found. CONCLUSIONS: The raised manganese superoxide dismutase and reduced copper/ zinc superoxide dismutase concentrations and activities in H pylori associated gastritis were reversed towards normal by successful treatment of the infection.     

Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide.

Superoxide dismutase reduces injury in many disease processes, implicating superoxide anion radical (O2-.) as a toxic species in vivo. A critical target of superoxide may be nitric oxide (NO.) produced by endothelium, macrophages, neutrophils, and brain synaptosomes. Superoxide and NO. are known to rapidly react to form the stable peroxynitrite anion (ONOO-). We have shown that peroxynitrite has a pKa of 7.49 +/- 0.06 at 37 degrees C and rapidly decomposes once protonated with a half-life of 1.9 sec at pH 7.4. Peroxynitrite decomposition generates a strong oxidant with reactivity similar to hydroxyl radical, as assessed by the oxidation of deoxyribose or dimethyl sulfoxide. Product yields indicative of hydroxyl radical were 5.1 +/- 0.1% and 24.3 +/- 1.0%, respectively, of added peroxynitrite. Product formation was not affected by the metal chelator diethyltriaminepentaacetic acid, suggesting that iron was not required to catalyze oxidation. In contrast, desferrioxamine was a potent, competitive inhibitor of peroxynitrite-initiated oxidation because of a direct reaction between desferrioxamine and peroxynitrite rather than by iron chelation. We propose that superoxide dismutase may protect vascular tissue stimulated to produce superoxide and NO. under pathological conditions by preventing the formation of peroxynitrite.     

安石榴苷减轻心肌缺血/再灌注损伤的作用及机制研究

目的 探讨安石榴甙（PUN）预先处理对心肌缺血/再灌注损伤（MI/RI）的作用及其机制。 方法 选取成年雄性SD大鼠,PUN 30 mg/（kg·d）生理盐水灌胃7 d后,建立心肌缺血再灌注（MI/R）模型。采用右侧颈总动脉插管检测心脏功能,用伊文思蓝和氯化三苯基四氮唑（TTC）双染检测心梗面积,测定血清肌酸激酶同工酶（CK-MB）和乳酸脱氢酶（LDH）活性反映心肌损伤,原位末端标记（TUNEL）法检测心肌细胞凋亡,比色法检测心肌丙二醛（MDA）含量和超氧化物歧化酶（SOD）的活性,蛋白免疫印迹检测磷酸腺苷活化蛋白激酶（AMPK）表达及磷酸化。 结果 PUN预先处理可改善MI/R后的心脏功能,减少心梗面积和心肌细胞凋亡,降低CK-MB和LDH的活性,降低心肌氧化应激,增加AMPK磷酸化（均P<0.05或P<0.01）,而使用AMPK抑制剂（compound c）可阻断PUN对MI/R的保护作用（P<0.05或P<0.01）。 结论 PUN预先处理可减轻MI/RI,其机制可能与其激活AMPK有关。     

Effect of brief regional ischemia followed by reperfusion with or without superoxide dismutase and catalase administration on myocardial sarcoplasmic reticulum and contractile function

The effect of reperfusion with and without free radical scavengers on sarcoplasmic reticulum and contractile function was examined in a canine model of 15-minute coronary artery occlusion followed by reperfusion. Dogs were reperfused with (n = 13) or without (n = 16) superoxide dismutase and catalase or were killed at 15 minutes of ischemia (n = 17). Superoxide dismutase and catalase were administered as a bolus (20,000 and 12,500 U/kg, respectively) beginning 1.25 minutes before reperfusion followed by infusion of 16,000 and 12,500 U/kg/hr, respectively. Sarcoplasmic reticulum function was evaluated from the rate of calcium uptake of unfractionated subepicardial, subendocardial, and transmural homogenates determined with and without ruthenium red to close the calcium release channel. Mechanical function was evaluated by means of sonomicrometry. Fifteen minutes of ischemia significantly (p less than 0.05) depressed the sarcoplasmic reticulum calcium uptake rate only in the subendocardium (from 25 +/- 2 to 14 +/- 1 nmol/min/mg without ruthenium red and from 60 +/- 3 to 49 +/- 3 nmol/min/mg with ruthenium red). Reperfusion with or without superoxide dismutase and catalase restored homogenate calcium uptake rates to normal, although severe contractile dysfunction persisted. This indicates that damage to the sarcoplasmic reticulum may not be the major cause of postreperfusion contractile dysfunction. Ischemia-reperfusion caused a decrease in systolic shortening from 19 +/- 2% to 1 +/- 2% with and from 18 +/- 1% to 4 +/- 1% without free radical scavengers (p = NS between groups). Thus administration of superoxide dismutase and catalase beginning shortly before reperfusion had no effect on postreperfusion contractile dysfunction or sarcoplasmic reticulum function.