Fully Balanced Fluids do not Improve Microvascular Oxygenation, Acidosis and Renal Function in a Rat Model of Endotoxemia.

The expectation of fluid therapy in patients with septic shock is that it corrects hypovolemia, with the aim of restoring tissue perfusion and oxygenation and organ function. This study investigated whether different types of resuscitation fluids were effective in improving renal microcirculatory oxygenation, acidosis, oxidative stress, and renal function in a rat model of endotoxemic shock. Five groups of rats were used: a sham group, a lipopolysaccharide (LPS) group, and three LPS groups that received 30 mL/kg/h of 0.9% sodium chloride (0.9% NaCl), a new bicarbonate buffered crystalloid solution closely resembling the composition of plasma (FB-Cxt) or a hydroxyethyl starch-ringer acetate solution. Systemic hemodynamic variables, renal blood flow, microvascular oxygenation, oxidative/nitrosative stress, and renal function were measured. LPS-induced shock was only partially resolved by fluid administration. Animals became arterially hypotensive despite adequate central venous pressure. Hydroxyethyl starch-ringer acetate was more effective at improving arterial pressures and renal blood flow than 0.9% NaCl or FB-Cxt. Fluids had marginal effects on pH and HCO3 levels irrespective of the buffer, or on renal µPO2 and dysfunction. Colloids increased the markers of renal oxidative stress (P < 0.001), whereas unbalanced crystalloids increased the markers of nitrosative stress during sepsis (P < 0.01). Endotoxemia-induced acidosis and decreases in renal µPO2 or renal injury were not corrected solely by fluid resuscitation, irrespective of the buffer of the fluid. Our study supported the idea that fluids must be supplemented by other compounds that specifically correct renal inflammation and oxygenation to be effective in resolving septic shock-induced renal failure.

Ascorbic acid improves renal microcirculatory oxygenation in a rat model of renal I/R injury.

BACKGROUND AND OBJECTIVES: Acute kidney injury (AKI) is a clinical condition associated with a degree of morbidity and mortality despite supportive care, and ischemia/reperfusion injury (I/R) is one of the main causes of AKI. The pathophysiology of I/R injury is a complex cascade of events including the release of free oxygen radicals followed by damage to proteins, lipids, mitochondria, and deranged tissue oxygenation. In this study, we investigated whether the antioxidant ascorbic acid would be able to largely prevent oxidative stress and consequently, reduce I/R-related injury to the kidneys in terms of oxygenation, inflammation, and renal failure. MATERIALS AND METHODS: Rats were divided into three groups (n = 6/group): (1) a time control group; (2) a group subjected to renal ischemia for 60 min by high aortic occlusion followed by 2 h of reperfusion (I/R); and (3) a group subjected to I/R and treated with an i.v. 100 mg/kg bolus ascorbic acid 15 min before ischemia and continuous infusion of 50 mg/kg/hour for 2 h during reperfusion (I/R + AA). We measured renal tissue oxidative stress, microvascular oxygenation, renal oxygen delivery and consumption, and renal expression of inflammatory and injury markers. RESULTS: We demonstrated that aortic clamping and release resulted in increased oxidative stress and inflammation that was associated with a significant fall in systemic and renal hemodynamics and oxygenation parameters. The treatment of ascorbic acid completely abrogated oxidative stress and inflammatory parameters. However, it only partly improved microcirculatory oxygenation and was without any effect on anuria. CONCLUSION: The ascorbic acid treatment partly improves microcirculatory oxygenation and prevents oxidative stress without restoring urine output in a severe I/R model of AKI.

Effects of Crataegus microphylla on vascular dysfunction in streptozotocin-induced diabetic rats.

Vascular dysfunction plays a key role in the pathogenesis of diabetic vascular disease. In this study, we aimed to investigate whether chronic in vivo treatment of Crataegus microphylla (CM) extract in diabetic rats induced with streptozotocin (STZ, intraperitoneal, 65 mg/kg) preserves vascular function and to evaluate whether the reduction of inducible nitric oxide synthase (iNOS), proinflammatory cytokines, and lipid peroxidation mediates its mechanisms of action. Starting at 4 weeks of diabetes, CM extract (100 mg/kg) was administrated to diabetic rats for 4 weeks. In aortic rings, relaxation to acetylcholine and vasoreactivity to noradrenaline were impaired, whereas aortic iNOS expression and plasma tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), total nitrite-nitrate, and malondialdehite levels were increased in diabetic rats compared with controls. Chronic CM treatment significantly corrected all the above abnormalities in diabetic rats. In comparison, pretreatment of the aorta of diabetic rats with N-[3(aminomethyl) benzyl]-acetamidine, dihydrochloride (10(-5) M), a selective inhibitor of iNOS, produced a similar recovery in vascular reactivity. These results suggest that chronic in vivo treatment of CM preserves endothelium-dependent relaxation and vascular contraction in STZ-induced diabetes, possibly by reducing iNOS expression in the aorta and by decreasing plasma levels of TNF-α and IL-6 and by preventing lipid peroxidation.

Acute effects of balanced versus unbalanced colloid resuscitation on renal macrocirculatory and microcirculatory perfusion during endotoxemic shock.

This study was designed to investigate the acute effects of balanced versus unbalanced colloid resuscitation on renal macrocirculatory and microcirculatory perfusions during lipopolysaccharide-induced endotoxemic shock in rats. We tested the hypothesis that balanced colloid resuscitation would be better for the kidney than unbalanced colloid resuscitation. Shock was induced by lipopolysaccharide (10 mg/kg i.v. over 30 min). When mean arterial pressure (MAP) was decreased to 40 mmHg, fluid resuscitation was started with either hydroxyethyl starch (HES130/0.42) dissolved in saline (HES-NaCl) as an unbalanced colloid solution or HES130/0.42 dissolved in Ringer's acetate (HES-RA) as a balanced colloid solution. Microvascular perfusion in the renal cortex was monitored using laser speckle imaging, and in addition, systemic hemodynamics, renal artery blood flow (RBF), and plasma ion levels were measured. Shock decreased MAP, led to anuria, and worsened all other parameters. Hydroxyethyl starch-NaCl improved MAP (P > 0.05) but did not improve RBF (P > 0.05), metabolic acidosis (P > 0.05), and plasma ion levels (P > 0.05). Hydroxyethyl starch-RA improved MAP (P < 0.05), RBF (P < 0.05), and renal microvascular perfusion (P < 0.05), but did not improve metabolic acidosis (P > 0.05) and plasma ion levels (P > 0.05). Both HES-NaCl and HES-RA treatment could normalize creatinine clearance but not fractional sodium excretion. In endotoxemic rats, balanced colloid (HES) resuscitation was shown to be superior to unbalanced colloid resuscitation in terms of improvement of renal macrovascular and microvascular perfusions. However, whether this results in improved renal function in the long term warrants further study.

Balanced vs unbalanced crystalloid resuscitation in a near-fatal model of hemorrhagic shock and the effects on renal oxygenation, oxidative stress, and inflammation.

BACKGROUND: The aim of the present study was to test the hypothesis that balanced crystalloid resuscitation would be better for the kidney than unbalanced crystalloid resuscitation in a rat hemorrhagic shock model. METHODS: Male Wistar rats were randomly assigned to four groups (n=6/group): (1) time control; (2) hemorrhagic shock control; (3) hemorrhagic shock followed by unbalanced crystalloid resuscitation (0.9% NaCl); and (4) hemorrhagic shock followed by acetate and gluconate-balanced crystalloid resuscitation (Plasma Lyte). We tested the solutions for their effects on renal hemodynamics and microvascular oxygenation, strong-ion difference, systemic and renal markers of inflammation and oxidative stress including glycocalyx degradation as well as their effects on renal function. RESULTS: The main findings of our study were that: (1) both the balanced and unbalanced crystalloid solutions successfully restored the blood pressure, but renal blood flow was only recovered by the balanced solution although this did not lead to improved renal microvascular oxygenation; (2) while unbalanced crystalloid resuscitation induced hyperchloremia and worsened metabolic acidosis in hemorrhaged rats, balanced crystalloid resuscitation prevented hyperchloremia, restored the acid-base balance, and preserved the anion gap and strong ion difference in these animals; (3) in addition balanced crystalloid resuscitation significantly improved renal oxygen consumption (increased VO(2), decreased [Formula: see text] ); and (4) however neither balanced nor unbalanced crystalloid resuscitation could normalize systemic inflammation or oxidative stress. Functional immunohistochemistry biomarkers showed improvement in L-FABP in favor of balanced solutions in comparison to the hemorrhagic group although no such benefit was seen for renal tubular injury (measured by NGAL) by giving either unbalanced or balanced solutions. CONCLUSIONS: Although balanced crystalloid resuscitation seems superior to balanced crystalloid resuscitation in protecting the kidney after hemorrhagic shock and is certainly better than not applying fluid resuscitation, these solutions were not able to correct systemic inflammation or oxidative stress associated with hemorrhagic shock.

The pathogenesis of acute kidney injury and the toxic triangle of oxygen, reactive oxygen species and nitric oxide.

Despite the identification of several of the cellular mechanisms thought to underlie the development of acute kidney injury (AKI), the pathophysiology of AKI is still poorly understood. It is clear, however, that instead of a single mechanism being responsible for its etiology, AKI is associated with an entire orchestra of failing cellular mechanisms. Renal microcirculation is the physiological compartment where these mechanisms come together and exert their integrated deleterious action. Therefore, the study of renal microcirculation and the identification of the determinants of its function in models of AKI can be expected to provide insight into the pathogenesis and resolution of AKI. A major determinant of adequate organ function is the adequate oxygen (O(2)) supply at the microcirculatory level and utilization at mitochondrial levels for ATP production needed for performing organ function. The highly complex architecture of the renal microvasculature, the need to meet a high energy demand and the borderline hypoxemic nature of the kidney makes it an organ that is highly vulnerable to injury. Under normal, steady-state conditions, the oxygen supply to the renal tissues is well regulated and utilized not only for mitochondrial production of ATP (mainly for Na reabsorption), but also for the production of nitric oxide and the reactive oxygen species needed for physiological control of renal function. Under pathological conditions, such as inflammation, shock or sepsis, however, the renal microcirculation becomes compromised, which results in a disruption of the homeostasis of nitric oxide, reactive oxygen species, and oxygen supply and utilization. This imbalance results in these compounds exerting pathogenic effects, such as hypoxemia and oxidative stress, resulting in further deterioration of renal microcirculatory function. Our hypothesis is that this sequence of events underlies the development of AKI and that integrated therapeutic modalities targeting these pathogenic mechanisms will be effective therapeutic strategies in the clinical environment.

The role of renal hypoperfusion in development of renal microcirculatory dysfunction in endotoxemic rats.

PURPOSE: To study the role of renal hypoperfusion in development of renal microcirculatory dysfunction in endotoxemic rats. METHODS: Rats were randomized into four groups: a sham group (n = 6), a lipopolysaccharide (LPS) group (n = 6), a group in which LPS administration was followed by immediate fluid resuscitation which prevented the drop of renal blood flow (EARLY group) (n = 6), and a group in which LPS administration was followed by delayed (i.e., a 2-h delay) fluid resuscitation (LATE group) (n = 6). Renal blood flow was measured using a transit-time ultrasound flow probe. Microvascular perfusion and oxygenation distributions in the renal cortex were assessed using laser speckle imaging and phosphorimetry, respectively. Interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-α were measured as markers of systemic inflammation. Furthermore, renal tissue samples were stained for leukocyte infiltration and inducible nitric oxide synthase (iNOS) expression in the kidney. RESULTS: LPS infusion worsened both microvascular perfusion and oxygenation distributions. Fluid resuscitation improved perfusion histograms but not oxygenation histograms. Improvement of microvascular perfusion was more pronounced in the EARLY group compared with the LATE group. Serum cytokine levels decreased in the resuscitated groups, with no difference between the EARLY and LATE groups. However, iNOS expression and leukocyte infiltration in glomeruli were lower in the EARLY group compared with the LATE group. CONCLUSIONS: In our model, prevention of endotoxemia-induced systemic hypotension by immediate fluid resuscitation (EARLY group) did not prevent systemic inflammatory activation (IL-6, IL-10, TNF-α) but did reduce renal inflammation (iNOS expression and glomerular leukocyte infiltration). However, it could not prevent reduced renal microvascular oxygenation.

Ischemic preconditioning affects hexokinase activity and HKII in different subcellular compartments throughout cardiac ischemia-reperfusion.

The glycolytic enzyme hexokinase (HK) is suggested to play a role in ischemic preconditioning (IPC). In the present study we determined how ischemic preconditioning affects HK activity and HKI and HKII protein content at five different time points and three different subcellular fractions throughout cardiac ischemia-reperfusion. Isolated Langendorff-perfused rat hearts (10 groups of 7 hearts each) were subjected to 35 min ischemia and 30 min reperfusion (control groups); the IPC groups were pretreated with 3 times 5-min ischemia. IPC was without effect on microsomal HK activity, and only decreased cytosolic HK activity at 35 min ischemia, which was mimicked by decreased cytosolic HKII, but not HKI, protein content. In contrast, mitochondrial HK activity at baseline and during reperfusion was elevated by IPC, without changes during ischemia. No effect of IPC on mitochondrial HK I protein content was observed. However, mitochondrial HK II protein content during reperfusion was augmented by IPC, albeit not following the IPC stimulus. It is concluded that IPC results in decreased cytosolic HK activity during ischemia that could be explained by decreased HKII protein content. IPC increased mitochondrial HK activity before ischemia and during reperfusion that was only mimicked by increased HK II protein content during reperfusion. IPC was without effect on the phosphorylation status of HK before ischemia. We conclude that IPC is associated with 1) a biphasic response of increased mitochondrial HK activity before and after ischemia, 2) decreased cytosolic HK activity during ischemia, and 3) cellular redistribution of HKII but not HKI.

The effect of alpha-lipoic acid on NOS dispersion in the lung of streptozotocin-induced diabetic rats.

Oxidative stress and impaired bioactivity of nitric oxide (NO) play an important role in the organ pathogenesis and angiopathic complications of diabetes mellitus. In this study, we evaluated the effects of alpha-lipoic acid (ALA) on nitric oxide synthase (NOS) in lung tissues. ALA is a strong antioxidant. We wonder how it can affect oxidative stress and NO in the lung cells and vessels of diabetic rats. Wistar rats were divided into four groups; control, diabetic [65 mg/kg streptozotocin (STZ) for 15 days], STZ+ALA-treated (65 mg/kg ALA every 2 days for 15 days), and ALA-only-treated animals. At the end of the experimental period, lipid peroxidation, superoxide dismutase (SOD), and inducible NOS (iNOS) and endothelial NOS (eNOS) distribution were evaluated. Oxidative stress decreased with ALA in diabetic animals, and SOD also increased with ALA. iNOS and eNOS increased in diabetic animals, and ALA prevented iNOS increment in lung tissues. As a result, ALA can prevent some diabetic effects on the lungs and can also protect from vascular damages.

The relationship between nitric oxide and leptin in the lung of rat with streptozotocin-induced diabetes.

Lung structural changes and immunoreactivity of endothelial (eNOS)- and inducible nitric oxide synthase (iNOS) were investigated by light microscopy in lungs of treated and untreated diabetic rats. Diabetes was induced by a single intraperitoneal (i.p.) injection of 65 mg kg(-1) streptozotocin (STZ) in Wistar albino male rats. Diabetic rats received daily i.p. doses of dexamethasone (2 mg kg(-1)), leptin (0.5 microg kg(-1)) and intramuscular insulin (20 U kg(-1)) or a combination of these drugs for 1 week starting 4 weeks after the STZ injections. After treatment, the blood levels of glucose, leptin, insulin and nitrate/nitrite (NO(3) (-)/NO(2) (-)) were measured. Dilatation of alveoli and alveolar ducts, partial alveolar wall thickening and increased eNOS- and iNOS characterized the diabetic rat lungs. High blood glucose and nitrate/nitrite levels as well as low insulin and leptin levels were also present. Treatment with insulin, dexamethasone and a combination of these drugs resulted in improvement of the structural and immunohistochemical abnormalities. The most effective treatment was insulin therapy. Leptin administration resulted in increased relative amounts of extracellular material, which led to noticeable respiratory efficiency in the diabetic rat lungs. All treatments except leptin lowered blood glucose levels. The combination of insulin and dexamethasone increased blood leptin and insulin, while the remaining diabetic rats had blood with low leptin and insulin concentrations. These results suggest that therapy with insulin plus dexamethasone but not therapy with leptin is beneficial for diabetics.

Effects of artichoke extract supplementation on gonads of cadmium-treated rats.

The present study was designed to determine whether artichoke (Cynara scolymus) exerts a protective effect on gonads of cadmium-treated rats and if there is a relationship between artichoke supplementation and nitric oxide (NO) formation in cells. Forty Wistar albino male rats, weighing an average of 90 g each, were equally divided into four groups receiving 1 mg/100 g cadmium chloride by injection (group 1), the same dose CdCl2 plus 3 mg/100 g artichoke extract (group 2), the same dose of artichoke extract (group 3), and male controls (group 4). Four additional groups, labeled 5-8, consisted of identically treated and control female rats. After 4 weeks of treatment, the animals were killed and their gonads were removed for histological examination. As expected, the seminiferous tubules and Leydig cells were damaged by cadmium. Ovarian tissue was not damaged to the same extent as testicular cells. Artichoke extract exerted a clear protective effect against Cd-induced testicular damage and lowered NO production to the same level of that in the control groups.

Effects of coenzyme Q10 on the heart ultrastructure and nitric oxide synthase during hyperthyroidism.

Coenzyme Q10 is an important component of mitochondrial electron transport chain and antioxidant. Hyperthyroidism manifests hyperdynamic circulation with increased cardiac output, increased heart rate and decreased peripheral resistance. The heart is also under the oxidative stress in the hyperthyroidism. The aim of this study was to examine both how the coenzyme Q10 can affect heart ultrastructure in the hyperthyroidism and how the relationship between nitric oxide synthase (NOS) and heart damage and coenzyme Q10. Swiss Black C57 mice received 5 mg/kg L-thyroxine. Coenzyme Q10 (1.5 mg/kg) and L-thyroxine together was given to second group mice. Coenzyme Q10 and serum physiologic were applied to another two groups, respectively. All treatments were performed daily for 15 days by gavage. Free triiodothyronine and thyroxine were increased in two groups given L-thyroxine; thyroid-stimulating hormone level did not change. Hyperthyroid heart showed an increased endothelial NOS (eNOS) and inducible NOS (iNOS) immunoreactivity in the tissue. Coenzyme Q10 administration decreased these NOS immunoreactivities in the hyperthyroid animals. Cardiomyocytes of the hyperthyroid animals was characterized by abnormal shape and invaginated nuclei, and degenerative giant mitochondria. Desmosome plaques reduced in density. In hyperthyroid mice given coenzyme Q10, the structural disorganization and mitochondrial damage regressed. However, hearts of healthy mice given coenzyme Q10 displayed normal ultrastructure, except for increased mitochondria and some of them were partially damaged. Coenzyme Q10 increased the glycogen in the cardiomyocytes. In conclusion, coenzyme Q10 administration can prevent the ultrastructural disorganization and decrease the iNOS and eNOS increment in the hyperthyroid heart.

Changes of nitric oxide synthase-containing nerve fibers and parameters for oxidative stress after unilateral cavernous nerve resection or manuplation in rat penis.

After pelvic surgeries such as radical prostatectomy, two major complications--urinary incontinence and erectile dysfunction (ED) may occur. Etiologies for ED are multiple pathologic mediators/systems. Oxidative stress, which is known to be induced after surgical trauma, could be a cause of ED. The purposes of in this study are to investigate the effect of unilateral manipulation/ dissection and resection of the cavernous nerve (neurotomy) to NOS (nitric oxide synthase)-containing nerve fibers and pressure after electro stimulation in rat corpus cavernosum, and to determine whether these procedures would produce oxidative stress within rat cavernous tissue 3 weeks and 6 months after the operation. Male rats were divided into 5 groups. Rats in groups 1 and 2 underwent unilateral cavernous nerve manipulation and sacrificed 3 weeks and 6 months after the operation, respectively. Rats in groups 3 and 4 underwent unilateral neurotomy of a 5-mm. segment of the cavernous nerve, and they were sacrificed 3 weeks and 6 months after nerve ablation, respectively. Group 5 rats were control animals for biochemical analysis. Intracavernous pressure following electro stimulation reduced is significantly 3 weeks after unilateral resection, as compared to that of the manipulated nerve (P < 0.05), and it recovered 6 months after neurotomy. The recovery was also confirmed by NADPH (nicotinamide adenine dinucleotide phosphate) diaphorase staining in neurotomy groups. Lipid peroxidation, which is an indicater of oxidative stress, was determined by measuring thiobarbituric acid reacting substance (TBARS) levels and superoxide dismutase (SOD) activity. These markers indicated that unilateral cavernous nerve manipulation or resection produced oxidative stress within rat corpus cavernosum. Oxidative stress was more prominent 3 weeks after unilateral neurotomy (P < 0.05). Also, compared to the control animal group, oxidative stress was observed three weeks after manipulation of unilateral cavernous nerve (P < 0.05). Resection of the cavernous nerve caused more prominent oxidative stress than in the manipulation group. This study suggested, that unilateral cavernous neurotomy caused a decrease of intra cavernous pressure and NOS fibers in rat corpus cavernosum, and they recovered 6 months after neurotomy. Our data also provided evidence that neurotomy and manipulation of the cavernous nerve caused oxidative stress in rat corpus cavernosum and that oxidative stress was more prominent in the nerve resection group.

Inhibition of inducible nitric oxide synthase in murine visceral larva migrans: effects on lung and liver damage.

The roles of nitric oxide production and oxidative process were studied in mice infected with Toxocara canis and treated with aminoguanidine which is a specific inhibitor of inducible nitric oxide synthase (iNOS). Relations of nitric oxide synthase inhibition and tissue pathology were assessed by biochemical, histological and immunohistochemical methods. In experiments, Balb/c albino mice were inoculated with T. canis eggs either with or without aminoguanidine treatment or alone, at 24th, 48th hours and on 7th days. LPx and SOD values in liver tissue and plasma were measured. Liver and lung tissues were evaluated for the pathological lesions. The expression of eNOS and iNOS in both tissues were studied with immunohistochemistry in the same intervals. We observed significant differences between T. canis infected and aminoguanidine treated animals. Larval toxocarosis led to oxidative stress elevation in plasma. Microscopic examination of the liver histological sections revealed pathological lesions in the hepatic parenchyma in infected mice. In the mice received T. canis eggs plus aminoguanidine, the sinusoidal areas were enlarged. Histological lesions were more severe at 48 hours after infection. Numbers of eNOS and iNOS expressing epithelial cells were increased in the T. canis infected mice. The activities of eNOS and iNOS were also observed in the body of the larvae which have migrated to lung and liver. As a result, we have demonstrated that in vivo production of eNO and iNO during T. canis infection cause direct host damages and it is strongly related to the oxidative stress. We propose that larval NO can also be effective in larval migration, but it needs further investigation on distribution of NO in larvae.

Short-term hyperglycemia increases endothelial glycocalyx permeability and acutely decreases lineal density of capillaries with flowing red blood cells.

Hyperglycemia is becoming recognized as an important risk factor for microvascular dysfunction. We hypothesized that short-term hyperglycemia, either on the scale of hours or weeks, alters the barrier function and the volume of the endothelial glycocalyx and decreases functional capillary density and deformability of the red blood cells (RBCs). All experiments were performed in anesthetized, mechanically ventilated, C57BL/6 mice that were either normoglycemic, acutely hyperglycemic (25 mM) for 60 min due to infusion of glucose, or hyperglycemic (25 mM) for 2-4 wk (db/db mice). The glycocalyx was probed using 40-kDa Texas red dextran, which is known to permeate the glycocalyx, and 70-kDa FITC dextran, which has impaired access to the glycocalyx in healthy animals. Clearance of the dye from the blood was measured. An orthogonal polarization spectral imaging technique was used to visualize the number of capillaries with flowing RBCs of the dorsal flexor muscle. The data indicate that short-term hyperglycemia causes a rapid decrease of the ability of the glycocalyx to exclude 70-kDa dextran. No change in the vascular permeation of 40-kDa dextran was observed. Glycocalyx volume was not affected by short-term hyperglycemia. In addition, 1 h of hyperglycemia resulted in a 38% decrease of the lineal density of capillaries with flowing RBCs. This decreased lineal density was not observed in the 2- to 4-wk hyperglycemia model. Short-term hyperglycemia was without any effect on the deformablity of the RBCs. The data indicate that the described increased vascular permeability with hyperglycemia can be ascribed to an increased permeability of the glycocalyx, identifying the glycocalyx as a potential early target of hyperglycemia.

Effects of orlistat and its relationship with nitric oxide in the small intestinal mucosa.

Nitric oxide (NO) is known to be a messenger molecule that plays an important role in physiological and pathological conditions. It is synthesized by an enzyme called nitric oxide synthase (NOS). Inducible NOS (iNOS), one of the three isomers of NOS, has both protective and toxic properties. In this study, the role of NO has been evaluated by gastrointestinal symptoms induced by orlistat which is used in obesity treatment. Orlistat was given to Wistar rats with and without iNOS inhibition. The effects of orlistat and inhibition of NOS were studied. Glucose, urea, alanine transaminase (ALT), and gamma glutamil transpeptidase (GGT) were descreased after short- and long- term orlistat applications. Dexamethasone increased level of these enzymes. Cholesterol and triglyceride were increased in all experimental groups than the controls. This increment was more severe in animals received orlistat and dexamethasone together. Small intestinal tissue also were researched histologically and NADPH-diaphorase (NADPH-d) histochemistrically. Orlistat caused histological damages in brush border membranes, connective tissues of villi, and lymphocyte migration also increased. Dexamethasone treatment prevented these damages partially while orlistat increased the NOS distribution in the tissue sections. Dexamethasone, which is an iNOS inhibitor, decreased NADPH-d histochemistry. There was a similiar NOS distribution both in the control and orlistat+dexamethasone group. Hence, we concluded that long- term trials with orlistat and similar drugs are needed.

In vivo inhibition of inducible nitric oxide and evaluation of the brain tissue damage induced by Toxocara canis larvae in experimentally infected mice.

Nitric oxide (NO) is known to be produced by macrophages, endothelial cells and neurons and synthesized by an enzyme called nitric oxide synthase (NOS). Various effector mechanisms and infections can affect the NO production. Excessive amount of NO will lead to biochemical reactions, which cause toxic effects. In this study the role of NO has been evaluated in larval toxocarosis, which is a systemic parasite infection caused by T. canis larvae. Infection was established in the Balb/c mice with or without inducible NOS (iNOS) inhibition and the effects of infection and NOS inhibition were observed according to the results of SOD and LPx measurements in brain tissue and NADPH-diaphorase (NADP-d) histochemistry. Results of NADPH-d histochemistry indicate that iNOS inhibition has protective effect on the brains of infected mice and that larval T. canis infection could be related to oxidative stress, and NO production and iNOS inhibition can protect the tissue from damage in this infection.

Arteriolar changes in nitric oxide activity and sensitivity during the course of streptozotocin-induced diabetes.

Nitric oxide (NO) may play an important role in the pathogenesis of diabetic microangiopathy. However, arteriolar changes in NO activity and sensitivity to NO may be dependent on both the type of arteriole and the duration of diabetes. Therefore, we assessed, in the in situ spinotrapezius muscle preparation of streptozotocin-diabetic rats and of controls, inside diameters of A2-A4 arterioles and the reactivity to topically applied acetylcholine and nitroprusside, before and after N(G)-nitro-L-arginine (L-NNA) at 2, 4, 6 and 12 weeks of diabetes. In A2 arterioles, basal diameters and the contribution of NO to basal diameter were not affected during the course of streptozotocin-induced diabetes. However, the maximal response to acetylcholine in these arterioles was attenuated after 2 until 4 weeks, and from 4 weeks on a sustained decrease in reactivity to sodium nitroprusside was observed. In A3 arterioles, both the basal diameter and the contribution of NO to basal diameter were decreased after 2 weeks and increased after 6 weeks, while the response to sodium nitroprusside was unaffected. In A4 arterioles, a significant increase in basal diameter was observed after 6 weeks only. Thus, this study shows that streptozotocin-induced diabetes causes microvascular changes in NO activity and sensitivity that depend on the type of arteriole. For each order of arteriole, these changes show a specific pattern during the course of diabetes.