Effects of T lymphocytes, interleukin-1, and interleukin-6 on renal fibrosis in canine end-stage renal disease

Canine end-stage renal disease (ESRD) is defined as the almost complete failure of renal function or irreversible destruction and is characterized by extensive glomerular sclerosis, tubular atrophy, interstitial inflammation, and fibrosis. Renal fibrosis is a common pathway leading to kidney failure. Infiltrating immunocytes in the end-stage kidney and several related factors are involved in renal fibrogenesis. A total of 18 renal tissue samples were obtained from canine patients with ESRD using biopsy and necropsy procedures. The extent of renal fibrosis was histopathologically examined by Masson trichrome staining. T-cell and B-cell localization and macrophage lineages were determined by immunohistochemical staining. Additionally, interleukin-1 (IL-1), IL-2, and IL-6 levels in the canine ESRD kidney were immunohistochemically evaluated and compared with expression patterns in the normal kidney. Significant fibrosis and infiltrating immunocytes consistent with lymphocytes were observed. Although the B-cell count was increased in the end-stage kidney, immunostaining patterns disclosed a marked increase in the number of CD3(+) cells. Furthermore, the remarkable increase in IL-1 and IL-6 levels suggests that T cells in the kidneys of dogs with ESRD spontaneously express these cytokines. In this study, the correlation between the degree of renal fibrosis and cytokines in canine ESRD was examined. The present study shows that T lymphocytes and IL-6 play important roles in renal fibrosis.     

The investigation of lipid peroxidation, anti-oxidant levels and some hematological parameters in sheep naturally infested with Wohlfahrtia magnifica larvae

Wohlfahrtia magnifica is the main agent of traumatic myiasis in many central and eastern European countries as well as in the Mediterranean basin and Asian countries. The present study was aimed to investigate the effect of myiasis infestation on lipid peroxidation, antioxidant levels and several hematological parameters in the sheep naturally infested with W. magnifica larvae. A total of 38 sheep, including 19 awassi sheep naturally infested with W. magnifica larvae and 19 clinically healthy awassi sheep, were studied. The infected animals were divided into three groups depending on the number of larvae (Group 1: <50 larvae; Group 2: 50-100 larvae; Group 3: >100 larvae). In blood samples, red blood cell counts, hemoglobin, hematocrit concentration and white blood cell, neutrophil, lymphocyte, eosinophil, basophil counts, plasma malondialdehyde, erythrocyte glutathione levels and erythrocyte glutathione peroxidase activity were studied. The results revealed a marked decrease in red blood cell counts and hemoglobin concentrations along with a significant increase in white blood cell and neutrophil counts. The elevation in plasma malondialdehyde levels, a function of lipid peroxidation, established a significant difference between the control group and groups 2, 3. Decreased activity of erythrocyte glutathione peroxidase was found significant in the control group and all parasitemia. We conclude that in natural infestations with W. magnifica, as in infestation with Lucilia cuprina, there is a notable increase in inflammatory activities resulting from the movements, secretions, and toxins of the larvae and form the toxins secreted by the bacteria - which leads to an impression of anemia - and that the tissue injury results in an increase in level of free radicals in the organism.     

Concentrations of strontium,barium, cadmium,copper, zinc,manganese, chromium,antimony, selenium,and lead in the liver and kidneys of dogs according to age,gender, and the occurrence of chronic kidney disease

This study was conducted to measure the concentrations of strontium (Sr), barium (Ba), cadmium (Cd), copper (Cu), zinc (Zn), manganese (Mn), chromium (Cr), antimony (Sb), selenium (Se), and lead (Pb) in canine liver, renal cortex, and renal medulla, and the association of these concentrations with age, gender, and occurrence of chronic kidney disease (CKD). Tissues from 50 dogs were analyzed using inductively coupled plasma mass spectrometry. Cu, Zn, and Mn levels were highest in the liver followed by the renal cortex and renal medulla. The highest Sr, Cd, and Se concentrations were measured in the renal cortex while lower levels were found in the renal medulla and liver. Female dogs had higher tissue concentrations of Sr (liver and renal medulla), Cd (liver), Zn (liver and renal cortex), Cr (liver, renal cortex, and renal medulla), and Pb (liver) than male animals. Except for Mn and Sb, age-dependent variations were observed for all element concentrations in the canine tissues. Hepatic Cd and Cr concentrations were higher in dogs with CKD. In conclusion, the present results provide new knowledge about the storage of specific elements in canine liver and kidneys, and can be considered important reference data for diagnostic methods and further investigations.     

Characterization of xenobiotic biotransformation in hepatic, renal and gut tissues of cattle and sheep

Microsomal and cytosolic preparations of hepatic, renal, ileal and ruminal tissues of cattle and sheep were used to measure oxidative, hydrolative and conjugative biotransformations of 11 xenobiotic substrates. Within species, enzyme activities were generally higher (P less than .05) in hepatic than non-hepatic tissue but, in both species, non-hepatic tissue exhibited considerable capacities for metabolizing certain substrates. Sheep rumen wall (with papillae) was notably high in cytochrome P-450 content (34% of hepatic value), in glutathione conjugation of ethacrynic acid (223% of hepatic activity; P less than .05), and UDP-glucuronidation of estrone (290% of hepatic activity; P less than .05). Sheep differed (P less than .05) from cattle, having lower cytochrome P-450 content in liver and ileum (but not kidney); lower N-demethylase activity in liver, but two- to threefold higher activity in kidney; lower sulfotransferase activity in liver and kidney; and higher glutathione S-transferase activity toward certain substrates. UDP-glucuronidation varied too widely among substrates to afford strong generalization in comparisons among tissues or between species. Non-hepatic tissues in ruminants exhibit considerable capacities for oxidative, hydrolative and conjugative metabolism of xenobiotics. Sheep and cattle differ widely in hepatic and non-hepatic capacities for biotransforming certain xenobiotics.     

The activity and properties of adenosine triphosphatase in various swine organs (liver, cerebral and kidney cortex, small intestinal mucosa)]

Studies into the activity of adenosine triphosphatase (ATPase) in homogenates of liver, cerebral cortex, renal cortex, and mucosa of small intestine of swine have shown differentiated activity patterns, with peak activity developing in the liver. This has been related to a particularly high metabolism performance of the liver in fattening pigs. No difference was found to exist between magnesium activation of ATPase of swine tissue homogenates and that in tissue obtained from ruminants. ATPase which could be activated by sodium and potassium ions and inhibited by ouabain was detectable from cerebral and renal cortex. Sodium and potassium ATPases accounts from some 25 per cent of the total activity. ATPase that could be stimulated by calcium ions was recorded only from liver homogenate. The optimum pH values of ATPase were between 7.5 and 8 in the liver, 9 in mucosa of small intestine, and 9.5 in cerebral and renal cortex.     

Sexual difference in ascorbic acid synthesis, tissue ascorbic acid and plasma total antioxidant capacity in mature chickens

1. An experiment was conducted with commercial White Leghorn type chickens to determine the effect of gender on tissue ascorbic acid concentration, antioxidant capacity and ascorbic acid synthesis. 2. Birds reared and maintained on litter were given a standard layer diet, without supplemental ascorbic acid, from 18 weeks of age. Tissue ascorbic acid concentration, plasma total antioxidant capacity and renal L-gulonolactone oxidase activity were measured at 30 weeks of age. 3. Females and males differed in ascorbic acid synthesis, as measured by renal L-gulonolactone oxidase activity, and tissue ascorbic acid concentration. 4. Plasma total antioxidant capacity and adrenal, gonadal, plasma and pituitary ascorbic acid concentrations were significantly higher in males, whereas ascorbic acid synthesis and splenic and thymic ascorbic acid concentrations were significantly higher in females. 5. L-Gulonolactone oxidase activity was not detected in the comb of cockerels.     

α-Luminol prevents decreases in glutamate, glutathione, and glutamine synthetase in the retinas of glaucomatous DBA/2J mice

Objective  To test the hypothesis that in DBA/2J mice, oxidative stress decreases glutamine synthetase (GS) levels resulting in a loss of neuronal glutamate and that the antioxidant α-luminol (GVT®) decreases this stress and glutamate loss in some types of glaucoma.
Animals  DBA/2J mice were separated into two groups, of which one was not treated, and the other treated with GVT in the drinking water. At 7 months of age, retinas were examined from five untreated DBA/2J mice, seven GVT-treated mice, and five C57BL/6 mice (negative controls).
Methods  Serial 0.5 μm plastic sections were immunogold stained for glutamate, GS, and total glutathione, followed by image analysis for staining patterns and density.
Results  Focal decreases in glutamate immunostaining were common in the inner nuclear layer (INL) of DBA/2J retinas, but not in C57BL/6 or GVT-treated DBA/2J retinas. Decreases in glutathione and GS immunostaining were found in DBA/2J retinal regions where neuronal glutamate immunostaining was reduced. Retinas from GVT-treated DBA/2J had no significant decreases in INL levels of glutamate, glutathione, or GS.
Conclusions  Retinas of dogs with primary glaucoma are reported to have focal depletion of neuronal glutamate. In DBA/2J mice, similar changes occur prior to the development of clinical disease. In these focal glutamate-depleted regions, levels of glutathione and GS are also reduced, consistent with the hypothesis that oxidative stress contributes to retinal changes in glaucoma. The ability of GVT, an antioxidant, to inhibit retinal abnormalities in DBA/2J mice provides further support for this hypothesis.     

Antioxidant Activity of Tocotrienol Rich Fraction Prevents Fenitrothion-induced Renal Damage in Rats

Fenitrothion (FNT) is an organophosphate compound widely used as pesticide in Malaysia. The present study aims to investigate effects of palm oil tocotrienol rich fraction (TRF) on the renal damage of FNT-treated rats. A total of 40 male Sprague Dawley rats were divided into 4 groups randomly, the control, TRF, FNT and FNT+TRF groups. FNT (20 mg/kg b.w.) and TRF (200 mg/kg b.w.) were given orally for 28 days continuously. Rats from the FNT+TRF group were supplemented with TRF 30 minutes prior to administration of FNT. Rats were sacrificed after 28 days, and the kidneys were removed for determination of oxidative stress and histological analysis. Plasma was collected for determination of blood creatinine and urea level. Statistical analysis showed that palm oil TRF has a protective effect against renal oxidative damage induced by FNT. In the FNT+TRF group, malondialdehyde and protein carbonyl levels were significantly lower, while the glutathione level as well as superoxide dismutase and catalase activities were significantly higher compared with the FNT-treated group (p<0.05). As for renal function, there was a markedly lower urea level (p<0.05) in the FNT+TRF group compared with the FNT-treated group, but there was no significant difference in creatinine level. Besides, total protein also showed no significant difference for all groups of rats (p>0.05). Histological evaluation also revealed that the FNT+TRF group had less glomerulus and renal tubule damage than the FNT-treated group. In conclusion, palm oil TRF was able to reduce oxidative stress and renal damage in FNT-treated rats.     

Heat shock-derived reactive oxygen species induce embryonic mortality in in vitro early stage bovine embryos

Heat shock is known to increase the mortality of early stage embryos, but the exact mechanism is unclear. In the present study, we investigated the possibility that the increased mortality is caused by heat shock-generated reactive oxygen species (ROS). The level of ROS was controlled by using beta-mercaptoethanol (beta-ME), a scavenger of ROS. In vitro-produced 8-cell stage embryos were cultured at 38.5 C or heat-shocked by exposure to 41 C for 6 h with 0, 10 and 50 microM beta-ME. Intracellular ROS levels were measured by a fluorescent dye, 2',7'-dichlorodihydrofluorescein diacetate (DCHFDA), and intracellular reduced form of glutathione (GSH) contents were estimated by another fluorescent dye, 4-chloromethyl-6,8-difluoro-7-hydroxycoumarin. Total glutathione content was estimated by the glutathione recycling assay. On day 8 after insemination, heat shock decreased the percentage of embryos that developed to the blastocyst stage and increased intracellular ROS levels, but there was no significant effect on the GSH and total glutathione contents. In contrast, beta-ME significantly decreased ROS levels in heat-shocked embryos and increased the GSH and total glutathione concentrations. Ten microM beta-ME significantly improved the viability of heat-shocked embryos. beta-ME caused no detrimental effects when it was added at normal culture temperature (38.5 C). These results indicate that ROS is the primary cause of increased embryonic mortality in heat-shocked early stage embryos.     

Betulinic acid prevents alcohol-induced liver damage by improving the antioxidant system in mice

Betulinic acid (BA), a pentacyclic lupane-type triterpene, has a wide range of bioactivities. The main objective of this work was to evaluate the hepatoprotective activity of BA and the potential mechanism underlying the ability of this compound to prevent liver damage induced by alcohol in vivo. Mice were given oral doses of BA (0.25, 0.5, and 1.0 mg/kg) daily for 14 days, and induced liver injury by feeding 50% alcohol orally at the dosage of 10 ml/kg after 1 h last administration of BA. BA pretreatment significantly reduced the serum levels of alanine transaminase, aspartate transaminase, total cholesterol, and triacylglycerides in a dose-dependent manner in the mice administered alcohol. Hepatic levels of glutathione, superoxide dismutase, glutathione peroxidase, and catalase were remarkably increased, while malondialdehyde contents and microvesicular steatosis in the liver were decreased by BA in a dose-dependent manner after alcohol-induced liver injury. These findings suggest that the mechanism underlying the hepatoprotective effects of BA might be due to increased antioxidant capacity, mainly through improvement of the tissue redox system, maintenance of the antioxidant system, and decreased lipid peroxidation in the liver.     

Effect of dietary calcium on selenium retention in postweaning swine

Two experiments were conducted to evaluate the effect of dietary Se and Ca on Se utilization in postweaning swine. Two levels of dietary Se (.3 or 5.0 ppm) supplemented as sodium selenite and four levels of total dietary Ca (.50, .80, 1.10 or 1.40%) in a 20% protein, corn-soybean meal diet were evaluated. Inorganic Ca was supplied from dicalcium phosphate and limestone. In Exp. I, 135 pigs weaned at 4 wk of age were allotted by sex, litter and weight and fed a basal diet for 7 d and then their treatment diets for a 28-d period. Plasma and tissue were collected at the end of the trial for Se concentration and glutathione peroxidase (GSH-Px) activity. Dietary Ca had no effect on gain or feed measurements but 5.0 ppm Se depressed daily gain slightly. When 5.0 ppm dietary Se was fed, there resulted higher liver, kidney, heart and longissimus muscle Se concentrations than when .3 ppm was provided, but dietary Ca had no effect on tissue Se values within each dietary Se level. Plasma GSH-Px increased when higher dietary Se was provided, whereas neither heart nor liver GSH-Px activity was affected by dietary Se or Ca level. In Exp. II, a 5-d balance trial was conducted with 32 barrows after adjustment to their treatment diet for a 28-d period. Selenium retention increased quadratically as dietary Ca increased, whereas Ca retention was not affected by dietary Se. These results suggest that low dietary Ca levels may reduce total Se retention but not Se metabolism within body tissue.     

Efficacy of dietary sodium selenite and calcium selenite provided in the diet at approved, marginally toxic, and toxic levels to growing swine.

A 2 x 3 factorial experiment conducted in three replicates of a randomized complete block design compared the effects of calcium selenite and sodium selenite at three different levels of Se (.3, 5, or 15 ppm) in the diets of growing swine on performance and tissue Se concentrations. Ninety pigs averaging 12.5 kg of BW were given ad libitum access to corn-soybean meal diets fortified with one of the treatment Se sources and dietary levels for a 35-d experimental period. Growth and feed intake were similar in pigs fed .3 and 5 ppm of Se but were lower (P less than .01) in those fed 15 ppm from either Se source. Serum Se increased (P less than .01) as dietary Se level increased with no difference between Se sources at each dietary Se level. Liver, kidney, and longissimus muscle Se concentrations increased (P less than .01) as the dietary level of Se increased and were similar when either Se sources was provided. These results indicate that calcium selenite was as effective as sodium selenite using the measurement criteria of growth, serum, and tissue Se concentrations and glutathione peroxidase activities of growing swine when fed at approved, marginally toxic, and toxic dietary Se levels.     

Adult-onset hypothyroidism in a lynx (Lynx canadensis).

A 19-yr-old female lynx (Lynx canadensis) presented for an acute onset of anorexia and reluctance to move. Physical examination, radiography, hematology, and serum biochemistry revealed evidence of renal failure, presumptive uremic gastritis, chronic intervertebral disk disease at T13-L1, and markedly low serum levels of total thyroxine (1.54 nmol/L) and total triixodothyronine (0.55 nmol/L). Twenty-five hours after its original presentation, the lynx exhibited horizontal nystagmus, which has been suggested as a clinical sign associated with hypothyroidism in domestic dogs. The lynx was euthanatized because of poor prognosis, and medical management concerns related to its chronic renal failure. Necropsy examination substantiated that the lynx had true hypothyroidism with 60-90% of the thyroid gland replaced with adipose tissue. Although feline adult-onset hypothyroidism may have low incidence, it should still be considered as a cause of nonspecific signs of disease in cats, as well as signs suggestive of hypothyroidism. Routine monitoring of baseline exotic felid thyroid levels throughout life would help to identify normal values and diagnose a potential disease that has obscure clinical signs.     

Effect of dietary cysteine supplements on canola meal toxicity and altered hepatic glutathione metabolism in the rat.

Experiments were conducted to determine the effects of feeding canola meal (Brassica campestris and Brassica napus) on the rat hepatic glutathione detoxification system and whether dietary cysteine supplements might modify such effects. Rats were fed test diets for 14 d. Body weight change, feed consumption, hepatic glutathione concentration, and hepatic glutathione-S-transferase (GSH-S-T) activities were determined. Weight gain was decreased when canola meal was fed, whereas hepatic glutathione concentrations increased, as did hepatic GSH-S-T activity. All effects correlated with total glucosinolate concentration in the canola meal. Dietary cysteine supplements, however, did not influence the growth reduction and increased hepatic glutathione concentrations caused by feeding canola meal. Supplemental cysteine prevented the elevation in hepatic GSH-S-T activity. The elevation in hepatic glutathione concentration caused by canola meals was not an overcompensation caused by an initial depletion and therefore reflected a general hepatotoxicity. Feeding supplemental cysteine increased hepatic glutathione levels at early time intervals and delayed the induction of GSH-S-T caused by canola meal toxicity. There was no beneficial effect of supplemental dietary cysteine in overcoming the toxicity of high levels of canola meal, but supplemental cysteine did modify the canola meal-induced changes in hepatic glutathione metabolism.     

Elemental composition, water, and total lipid content in peripheral nerves, spinal cord and brain of healthy adult dogs

Peripheral nerves, spinal cord, and brain of healthy adult dogs were analysed biochemically for sodium, potassium, calcium, magnesium, copper, zinc, iron, aluminium, silicon, total chloride, total tissue water and total lipid content. Flame atomic absorption spectrophotometry was used for elemental quantitation of the hydrochloric acid tissue extracts. Cerebrum and spinal cord had similar values for all parameters measured. Total sodium values were higher in nerves compared to central nervous system (CNS) (brain and spinal cord), while respective values for potassium were lower. Tissue levels of calcium, iron and silicon were comparable in brain, spinal cord and nerves. However, magnesium concentrations were two to three times higher in CNS than in nerves; and the reverse was true for aluminium levels. Tissue concentrations of zinc and copper were marginally higher in CNS than in nerves.     

Impact of thermal stress exposure on seminal quality,antioxidant defence system,TNF-α and TIMP-3 in Ossimi ram

Heat stress (HS) occupies huge importance nowadays as it leads to severe economic losses especially in livestock. Preserving sheep against HS is one of the governmental scopes where it represents huge percentage of global ruminant. The present research was conducted to study semen quality, some stress and inflammatory markers in Ossimi rams under both hot and mild climatic conditions. The current study was conducted on selected 46 ram samples divided into two groups during summer and winter. Semen analysis, testosterone (TES), cortisol (COR) and blood glucose (BG) levels, and lipid and protein profiles were done. Concentrations of tumour necrosis factor alpha (TNF-α), tissue inhibitor of metalloproteinase-3 (TIMP-3), nitric oxide (NO), malondialdehyde (MDA) and reduced glutathione (GSH) and specific activity of glutathione peroxidase (GPx) and superoxide dismutase (SOD) were assessed. The results in summer compared to winter revealed significant elevation of total defects and number of dead sperms; however, there was reduction in sperm total motility and concentration and external epididymal tail duct diameter. Histological study of epididymal tail lumen exhibited azoospermia. Further, TES, TIMP-3 and GSH levels were decreased and COR, TNF-α, NO and MDA were raised. Specific activities of GPx and SOD were also declined. Additionally, there was a significant increase in concentrations of BG and lipid profiles except high-density lipoprotein. Our data concluded that there were new insights into TNF-α and TIMP-3 as biomarkers can be used in diagnosis of sheep suffering from HS, but further studies are recommended to do in future work about such aspect.     

锰对1~4周龄五龙鹅血清脂类代谢、抗氧化指标及器官组织中锰沉积量的影响

本试验旨在研究饲粮中不同锰水平对1~4周龄五龙鹅血清脂类代谢、抗氧化指标及器官组织中锰沉积量的影响,以确定鹅饲粮中锰适宜添加水平。试验选用1日龄体重相近的五龙鹅360只,随机分为6个组,每组6个重复,每个重复10只鹅(公母各占1/2)。对照组(Ⅰ组)饲喂基础饲粮(锰含量为20 mg/kg),试验组分别饲喂在基础饲粮中添加30(Ⅱ组)、60(Ⅲ组)、90(Ⅳ组)、120(Ⅴ组)和150 mg/kg锰的试验饲粮(Ⅵ组)。试验期4周。结果表明:1)Ⅳ、Ⅴ、Ⅵ组血清甘油三酯和总胆固醇含量极显著高于Ⅰ组(P0.01),Ⅲ组显著高于Ⅰ组(P0.05)。各组血清碱性磷酸酶活性差异不显著(P0.05)。2)Ⅳ、Ⅴ、Ⅵ组血清总抗氧化能力和谷胱甘肽过氧化物酶活性极显著高于Ⅰ组(P0.01),Ⅲ组显著高于Ⅰ组(P0.05);Ⅴ组血清丙二醛含量极显著低于Ⅰ、Ⅱ、Ⅲ组(P0.01),Ⅳ、Ⅵ组显著低于Ⅰ、Ⅱ、Ⅲ组(P0.05)。3)Ⅳ、Ⅴ、Ⅵ组血清、心脏、肝脏和胰脏中锰沉积量极显著高于Ⅰ组(P0.01),Ⅱ、Ⅲ组血清、心脏和肝脏中锰沉积量显著高于Ⅰ组(P0.05)。由此可见,饲粮中添加锰能提高五龙鹅血清甘油三酯、总胆固醇含量,增强机体抗氧化能力,增加器官组织中锰沉积量。建议鹅饲粮中锰适宜添加水平为90~120 mg/kg。     

Comparative analysis of commercial renal diets for cats, with emphasis on their fatty acid composition

The objective of this study was to compare renal diets for cats that are commercially available in The Netherlands. The diets were analysed and their composition compared with a guideline proposed by the authors. Special attention was paid to the fatty acid composition of the diets and the role of fatty acids in the progression of chronic renal failure. On the basis of a total score for nutrient levels relative to the guideline recommendations, the diets were ranked as to expected efficacy.     

The porcine erythropoietin gene: cDNA sequence, genomic sequence and expression analyses in piglets

The porcine erythropoietin (EPO) gene and its cDNA have been cloned and characterized. The cDNA encodes a protein of 194 amino acids. The gene structure and sequence show a high degree of homology to the corresponding human and murine gene. Steroid hormone receptor binding sites are present both in the promoter and in the 3' flanking region of the gene, which also contains an oxygen-sensing sequence. The promoter lacks classical promoter elements such as TATA and CAAT boxes. Expression analyses using a competitive RT-PCR assay showed that the kidneys contain about ten times more erythropoietin mRNA than the liver in five-week-old piglets, thus indicating that the shift from mainly hepatic to mainly renal EPO production has taken place at this age. The testes showed a higher ratio of EPO mRNA to total RNA than the liver. Spleen showed very low levels of expression, while no expression of erythropoietin mRNA was detected in brain tissue, bone marrow, lung, lymph nodes, and ovaries.     

Systemic and pituitary pars intermedia antioxidant capacity associated with pars intermedia oxidative stress and dysfunction in horses

OBJECTIVE: To determine whether a deficiency in systemic or local (pars intermedia) antioxidant capacity is associated with pituitary pars intermedia oxidative stress and pituitary pars intermedia dysfunction (PPID) in horses. SAMPLE POPULATION: Blood samples from 20 horses with PPID and 20 healthy client-owned horses, archived paraffin-embedded adrenal gland and substantia nigra tissues from 20 horses, and pituitary gland tissue from 16 horses. PROCEDURES: Total glutathione, superoxide dismutase, and glutathione peroxidase activities were determined in RBCs. Accumulation of a systemic marker of oxidative stress (3-nitrotyrosine) was assessed in plasma and formalin-fixed, paraffin-embedded adrenal gland and substantia nigra tissues. Local antioxidants (total and manganese superoxide dismutase, glutathione peroxidase, and total glutathione) were measured in pars intermedia tissues. RESULTS: No significant differences existed in systemic antioxidant enzyme activity or accumulation of 3-nitrotyrosine between horses with PPID and control horses. In pituitary gland tissues, glutathione peroxidase activity was increased in horses with oxidative stress, whereas total glutathione concentration and superoxide dismutase activity remained unchanged. There was an age-associated decrease in manganese superoxide dismutase activity in the pars intermedia. CONCLUSIONS AND CLINICAL RELEVANCE: There was no evidence of systemic accumulation of oxidative stress markers or deficiencies in antioxidant capacity in horses with PPID, suggesting that these are unlikely to be major predisposing factors in the development of PPID. Manganese superoxide dismutase activity in the pars intermedia decreased significantly with increasing age. Role of an age-associated decrease in antioxidant capacity for the pars intermedia in the development of PPID in horses warrants further investigation.