Effects of whole blood viscosity and plasma NOx on cardiac function and cerebral blood flow in children with chronic kidney disease

Background/aim: The aim of the study was to investigate the effects of whole blood viscosity and plasma nitric oxide on cerebral and cardiovascular risks associated with chronic kidney disease. Materials and methods: The study group consisted of 40 pediatric patients and 21 healthy control subjects. Hematologic and biochemical variables, viscosity and plasma nitric oxide levels, echocardiographic findings, and middle cerebral artery blood flow velocity were examined. Results: Viscosity values of patients were significantly lower than those of the control group. Lower values of hematocrit, total protein, and albumin and higher values of ferritin in all patient groups resulted in significantly low viscosity levels. Plasma nitric oxide levels were higher in all patient groups than those in the controls. No statistically significant difference was present in middle cerebral artery blood flow velocity between the patient and control groups. Even when systolic functions were normal, the patient group had significant deterioration in diastolic functions, suggesting morbidity and mortality risks. Conclusions: Cerebral blood flow velocities were not affected by viscosity and nitric oxide levels, suggesting that cerebral circulation has the ability to make adaptive modulation. The metabolism of nitric oxide levels needs further investigation and studies in patients with chronic renal disease.

The long-term effects of progesterone-only contraceptives on endometrium and ovary in rats.

Progestin-only (p-only) contraceptives often cause breakthrough bleeding for unknown reasons. In this study, we aimed to evaluate the long-term effects of p-only contraceptives to gain a better understanding of breakthrough bleeding mechanism. Wistar rats were divided into etonorgesterel implant (Group 1, n = 25), depot medroxyprogesterone acetate injectable (Group 2, n = 25), and control groups (n = 5). Five rats each from groups 1 and 2 were examined every 10 days for up to 50 days after the medication. Uteri and ovaries were removed and prepared for immunohistochemistry and scanning electron microscopy. The tissue nitric oxide (NO) levels were determined by Griess reaction. Dynamic changes of endometrial estrogen and progesterone receptor immunoreactivity were observed in a time-dependent manner in groups 1 and 2. The number of endometrial pinopodes, which are small endometrial protrusions, increased in both groups. There was no difference between groups for the estrogen receptor in the surface epithelium of the ovary. Estrogen-alpha and progesterone receptor in follicular cells decreased in a time-dependent manner. The granulosa cells underwent atrophic and were disorganized. Decreased levels of uterine tissue NO were determined in groups 1 and 2. The effect of some p-only contraceptives make some dynamic changes in the endometrium, ovaries, steroid hormone receptors, cell morphology, and biochemical features of the tissues during their use.

The Effect of Hepcidin on Cardiac Ischemia-Reperfusion Injury.

Background/aim: Hepcidin is the main hormone in the regulation of iron metabolism which is also released from the heart. The aim of our study was to investigate the effects of hepcidin on the cardiac ischemia-reperfusion injury.Materials and methods: In this study, 12 Wistar albino rats were divided into two groups (n = 6 each): 1) The ischemia-reperfusion group (Group 1); 2) Hepcidin-treated group (Group 2). Rat hearts were perfused on Langendorff system with KH (Krebs-Henseleit) and subjected to 30 min stabilization, 30 min global ischemia, and 30 min reperfusion. Hepcidin (- M) was applied to group 2 at the onset of ischemia. Malondialdehyde (MDA), glutathione (GSH), and nitric oxide (NOx) levels were measured in heart tissue for NOx levels, viscosity, and ion content of perfusate were collected before ischemia and the 1st, 5th, 10th, 20th, and 30th minutes of reperfusion were determined. Apoptosis in heart was evaluated.Results: NOx and MDA levels significantly decreased in heart tissue in Hepcidin-treated group. NOx and viscosity of perfusate were not significantly different between the groups. Perfusate iron, calcium, magnesium, potassium, and sodium levels in group 2 were more homogeneous. Histologic structures of heart tissue were regularly in group 2. Apoptosis were increased in control group compared to hepcidin treated group.Conclusion: These results suggest that hepcidin may have a protective effect on the heart for the ischemia-reperfusion injury.

Maternal and umbilical venous adrenomedullin and nitric oxide levels in intrauterine growth restriction.

OBJECTIVE: To verify whether adrenomedullin (AM) and nitric oxide (NO) concentrations are changed in the maternal and fetal circulation in pregnancies complicated by intrauterine growth restriction (IUGR) compared to normal pregnancies, and to determine any relationship between them. METHODS: Forty-six small for gestational age (SGA) and 34 appropriate for gestational age (AGA) infants were included in the study. Umbilical and maternal venous AM and NO concentrations were determined. RESULTS: Umbilical NO concentrations in SGA infants (mean +/- SD; 176.2 +/- 75.8 micromol/L) were significantly greater than in AGA infants (143.4 +/- 39.2 micromol/L) (p = 0.015). However, umbilical AM concentrations were similar in SGA and AGA infants with 14.2 +/- 4.4 pmol/mL and 14.5 +/- 6.2 pmol/mL, respectively (p > 0.05). There was no relationship between NO and AM levels in umbilical blood (r = 0.09, p = 0.40). No difference was found between either AM or NO levels in the maternal plasma of the two groups. CONCLUSIONS: We suggest that NO is increased in the fetoplacental circulation in SGA infants probably as a response to decreased blood flow, whereas AM is not. Additionally, increased NO in the fetoplacental circulation was found to be independent from AM secretion.

Effects of different resistance exercise protocols on nitric oxide, lipid peroxidation and creatine kinase activity in sedentary males.

The purpose of this study was to determine the changes of oxidative response and exercise-induced muscle damage after two different resistance exercise protocols. Whether training with low or high intensity resistance programs cause alterations in the activities of lipid peroxidation, nitric oxide (NOx), and creatine kinase (CK) activity in human plasma was investigated. Twenty untrained males participated into this study. Ten of the subjects performed high intensity resistance (HR) exercise circuit and the rest of them performed low intensity resistance (LR) exercise circuit of 4 different exercises as a single bout. Venous blood samples were drawn pre-exercise, immediately after the exercise, and at the 6(th), 24(th), 48(th) and the72(nd) hours of post-exercise. Samples were analyzed for markers of muscle damage (CK), lipid peroxidation (MDA) and NOx. NOx production increased in HR group (p < 0.05). The MDA response to the two different resistance exercise protocol in this study caused a significant increase between pre and post-exercise values in both groups (p < 0.05). Also, there was a significant difference in the MDA level between the two groups in post-exercise values (p < 0.05) and higher values were observed in HR group. CK activities showed a significant increase in all post exercise values (p < 0.05) of both groups but there were no difference between HR and LR groups. These findings support that high intensity resistance exercise induces free radical production more than low intensity resistance exercise program. Key pointsHigh intensity resistance exercise caused increases in NOx, MDA and CK levels.Light intensity resistance exercises increased MDA and CK levels but did not affect NOx levels.Damage arose during resistance exercises may be related to the level of resistance applied.

The effects of iron treatment on viscosity in children with cyanotic congenital heart disease.

OBJECTIVE: This study was planned to determine the effects of iron treatment in children with cyanotic congenital heart disease. METHOD AND MATERIALS: A total of 39 patients with cyanotic congenital heart disease including 20 (51%) females, 19 (49%) males and whose mean age was 9.9 ± 6.2 years, average weight was 33 ± 18.4 kg were evaluated. Patients were categorized into two groups as having iron deficiency and no iron deficiency with respect to their ferritin levels. 4 mg/kg/day iron treatment with two valences was applied to the groups with iron deficiency for 3 months. Clinical and laboratory findings of both groups were assessed at the outset and 3 months later and viscosity measurements were carried out. RESULTS: Iron deficiency was identified in 21 (53.8%) out of 39 patients. Average Hb and Hct values following 3-month iron treatment increased from 14.8 ± 2.4 g/dl to 16.0 ± 2.0 (P = 0.003) and from %45.8 ± 7.5 to %47.6 ± 7.2 (P = 0.052), respectively. Average viscosity value, however, was 5.6 ± 1.0 cP, it reduced to 5.5 ± 1.0 cP value by demonstrating very little reduction (P = 0.741). Nevertheless, O2 sat value increased from 71.7 to 75% and complaints such as headache, visual blurriness, having frequent sinusitis decreased. CONCLUSIONS: It was observed that iron treatment increased Hb and Hct levels in patients with cyanotic congenital heart disease without raising viscosity and it ensured improvement in clinical symptoms.

Antioxidant effect of vitamin E in the treatment of nutritional iron deficiency anemia.

Oxidant status and antioxidants play important roles in anemias. The present study was conducted to investigate the oxidant-antioxidant status in iron deficiency anemia (IDA), and to evaluate the antioxidant effect of vitamin E in IDA treatment. Ten patients with IDA aged nine months were given only iron treatment, whereas another 10 patients were administered both iron and vitamin E. The complete blood count, plasma malonyldialdehyde (MDA) level, erythrocyte superoxide dismutase level, and the serum vitamin E level, both before and within the treatment phases were examined. The reticulocyte count at the first week of treatment was found lower in the vitamin E-treated group. The mean corpuscular volume (MCV) was found higher in the vitamin E-treated group at the end of therapy. The malonyldialdehyde levels of the group treated with vitamin E were found lower during treatment. These results suggest that iron administration in IDA treatment may stimulate lipid peroxidation, and that vitamin E supplied with iron may reduce the MDA production. The hematological indications of the findings of our study are that the reticulocyte response develops earlier and the microcytosis recovery occurs more rapidly in the vitamin E-administered group in comparison with the group treated with iron only.

Evaluation of oxidant stress in Wilson's disease and non-Wilsonian chronic liver disease in childhood.

BACKGROUND/AIMS: Oxygen free radicals have an important role in the pathogenesis of acute and chronic liver disease. Free radical formation and oxidative damage, probably mediated with copper accumulation, are important in Wilson's disease pathogenesis. This study was performed to determine if accumulating copper in Wilson's disease is a cause of further oxidant stress compared to non-Wilsonian liver disease. METHODS: In this study, we investigated plasma malondialdehyde and nitric oxide levels to estimate the oxidant stress and total antioxidant capacity and vitamin E/cholesterol, vitamin C and beta-carotene levels to estimate the antioxidant status of patients. The groups investigated included 24 patients with Wilson's disease (group I), 25 patients with non-Wilsonian chronic liver disease (group II) and 23 healthy controls (group III). Wilson's disease and non-Wilson's disease patients were divided into subgroups according to disease stage (i.e. chronic hepatitis and cirrhosis) and all parameters were compared between subgroups and controls. RESULTS: Malondialdehyde and nitric oxide levels were higher than controls in groups I and II (p=0.013, p=0.01), but these levels did not differ between the Wilson's disease and non-Wilson's disease groups. The parameters were also evaluated with respect to the disease stage (i.e. chronic hepatitis and cirrhosis), and there was no difference between groups I and II. Although malondialdehyde and nitric oxide levels were significantly different between both disease stage groups and the controls, we observed decreased vitamin C and beta-carotene levels only in cirrhosis stage (p=0.01, p=0.01). CONCLUSIONS: We observed the presence of oxidant stress unrelated to the etiology of the liver disorder in our study. Deficiency of the major antioxidants, vitamin C and beta-carotene, develops as the disease stage advances from chronic hepatitis to cirrhosis.

Increased plasma nitrate levels in patients with crush syndrome in the Marmara earthquake.

BACKGROUND: Crush syndrome has been described as extensive muscle damage, leading to acute renal failure. The aim of this study was to evaluate the possible role of nitric oxide, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) in crush syndrome. PATIENTS AND METHODS: A total of 17 patients suffering from crush syndrome, 7 patients without crush syndrome and 10 healthy controls were enrolled in the study. Plasma nitrate, TNF-alpha, IL-1 beta levels and biochemical parameters were measured. RESULTS: All patients with crush syndrome demonstrated acute renal failure. Plasma nitrate levels were elevated significantly in the crush syndrome patients compared with patients without crush syndrome (33.5 +/- 20.1 vs. 15.3 +/- 5 micromol/l, p=0.014). There was no significant difference in TNF-alpha and IL-1 beta levels between control and patient groups. CONCLUSION: Increased plasma nitrate levels in the crush syndrome may be related either to the elevated production of NO or the diminished excretion of nitrate or both.

Cerebrospinal fluid levels of nitric oxide and nitrotyrosine in neonates with mild hypoxic-ischemic encephalopathy.

The objective of this study was to determine the role of cerebral nitric oxide and its powerful oxidant peroxynitrite following mild birth asphyxia. The cerebrospinal fluid levels of nitric oxide and 3-nitrotyrosine as a marker for peroxynitrite are measured in neonates with mild hypoxic-ischemic encephalopathy. Based on the classification of Sarnat and Sarnat, term neonates with mild hypoxic-ischemic encephalopathy and neurologically normal neonates suspected of sepsis were taken as the control group. Nitric oxide measurements were done by chemiluminescence, and nitrotyrosine measurements were made by high-performance liquid chromatography. The Mann Whitney U-test was used, and a Pvalue < .05 was considered significant. Eleven patients with grade 1 hypoxic-ischemic encephalopathy and nine controls were included. The gestational age and birthweights were similar in both groups. Neither of the cerebrospinal fluid levels of nitric oxide (8.60 +/- 0.49 micromol/L) and nitrotyrosine (0.45 +/- 0.33 micromol/L) of the neonates with hypoxic-ischemic encephalopathy showed significant differences from that of the means of nitric oxide (8.66 +/- 1.07 micromol/L) and nitrotyrosine levels (0.25 +/- 0.13 micromol/L) of the controls. These data suggest that the oxidative stress is not overexpressed to lead nitric oxide and peroxynitrite to play a pathologic role in the early phase of mild hypoxic-ischemic encephalopathy of the newborn.

Cerebrospinal fluid and serum vascular endothelial growth factor and nitric oxide levels in newborns with hypoxic ischemic encephalopathy.

Excitatory amino acids, cytokines and nitric oxide (NO) have been studied in the etiology and pathogenesis of hypoxic ischemic encephalopathy (HIE) of the newborn. Vascular endothelial growth factor (VEGF) is a known mediator of angiogenesis and has been shown to induce vascular proliferation and permeability via NO-mediated mechanism during hypoxia. The objective of this study was to investigate the cerebrospinal fluid and serum VEGF and NO levels in different stages of HIE and the correlation between the two mediators. Cerebrospinal fluid (CSF) and serum samples of 19 newborns with HIE and 13 controls were obtained within the first 24 h of life and kept at -70 degrees C until the time of measurement. NO levels were determined by Sievers NOA by chemiluminescence method and VEGF levels were measured by the enzyme-linked immunosorbent assay double sandwich method. The NO levels in CSF were higher than the control and mild HIE group in newborns with moderate to severe HIE, and VEGF levels in CSF were higher in the mild HIE group compared to controls but similar in the moderate to severe HIE group compared to mild HIE and control patients. There was no difference between groups with regard to serum NO or VEGF levels, and no correlation was observed between NO and VEGF levels both in CSF and serum samples. Depending on the severity of the hypoxic insult the stimulus for NO production by VEGF may have variable effects on endothelial cells which may give rise to the current results.

Serum levels of nitric oxide end products and interactions with lipoproteins in patients with coronary artery disease.

The purpose of this study was to examine whether the serum levels of nitric oxide end products and the ratio of nitrite to lipoproteins are valid instruments in the clinical follow-up of patients with coronary artery disease. 65 subjects were divided into three groups, including patients with coronary artery disease, silent coronary artery disease and controls. The serum nitrite level and also the ratio of nitrite to high-density lipoprotein were significantly different between the groups. According to the number of obstructed arteries, the serum nitrite level and the ratio of nitrite to high-density lipoprotein were found statistically different between the groups. There was a positive correlation between the serum nitrite level and the ratio of nitrite to high-density lipoprotein and the number of obstructed arteries. In conclusion, the serum nitrite level and ratio of nitrite to high-density lipoprotein may provide a beneficial guide to follow-up the status of patients with coronary artery disease.

The effects of losartan and enalapril therapies on the levels of nitric oxide, malondialdehyde, and glutathione in patients with essential hypertension.

Several recent studies have shown that essential hypertension is associated with increased oxidative stress, which may cause hypertension via enhanced oxidation and inactivation of nitric oxide. In this study, we investigated the malondialdehyde, nitric oxide, and glutathione levels in newly diagnosed essential hypertensive patients and whether or not there was any effect of antihypertensive treatment with angiotensin II type 1 receptor antagonist, losartan or angiotensin converting enzyme inhibitor, enalapril on plasma malondialdehyde, nitric oxide, and glutathione values. We selected 17 patients (F/M: 10/7, mean age: 46.12 +/- 9.2 years) for enalapril therapy (10-20 mg/d) and 14 patients (F/M: 8/6, mean age: 47.7 +/- 7.5 years) for losartan therapy (50-100 mg/d), and compared them with 12 normotensive controls. At the beginning of the study, both treated groups showed significantly higher plasma malondialdehyde and lower glutathione and nitric oxide in exhaled air compared to the control group. After 9 weeks of enalapril and losartan treatment, both systolic and diastolic pressure were significantly reduced. Both enalapril and losartan produced a significant decrease in plasma malondialdehyde and a significant increase in plasma glutathione levels and nitric oxide in exhaled air after 9 weeks. Initial values of plasma nitrate levels in patient groups were similar to the control group and increased significantly after the treatment period. In conclusion, both losartan and enalapril may be regulators between oxidant stress and the antioxidant system.

Relationship between interleukin-6 levels and ambulatory blood pressure in women with polycystic ovary syndrome.

OBJECTIVE: To determine 24-hour ambulatory blood pressures (ABP) in patients with polycystic ovary syndrome (PCOS) and its relationship with interleukin-6 (IL-6). DESIGN: Prospective controlled study. SETTING: University hospital. PATIENT(S): Fifty-four PCOS patients. INTERVENTION(S): Ambulatory blood pressure monitoring was conducted. Anthropometric, hormonal, metabolic, and inflammatory parameters, including plasma IL-6, C-reactive protein (CRP), fibrinogen, and nitric oxide (NO), were measured in each subject. MAIN OUTCOME MEASURE(S): Ambulatory blood pressure and plasma IL-6, CRP, fibrinogen, and NO. RESULT(S): Serum IL-6 levels of PCOS women in the highest systolic blood pressure (SBP) quartile were significantly higher than those of women in the lowest SBP quartile. The high serum IL-6 levels (serum IL-6 level>or=5.1 pg/mL) were associated with a higher probability of raised SBP (>/=126 mm Hg), with an odds ratio of 2.2 (95% confidence interval 0.8-7.9). The systolic and diastolic (DBP) blood pressures were significantly related to serum IL-6 levels. The IL-6 levels were positively and significantly correlated with serum CRP levels. Interleukin-6 and CRP were negatively and significantly correlated with serum NO levels. CONLUSION(S): The results suggest that raised plasma IL-6 levels may be related to ambulatory SBP and DBP in PCOS.

Is oxidative damage in operation in patients with hereditary spastic paraparesis?

Oxidative stress resulting from increased free radical production and/or defects in antioxidant defences may be the cause of various neurodegenerative disorders. In this study, the roles of oxygen free radicals, nitric oxide, superoxide dismutase, vitamin E and vitamin C were investigated in pure and complicated hereditary spastic paraparesis (HSP) patients. The results showed that plasma SOD, vitamin E and nitric oxide levels were significantly low in HSP patients. These findings indicate the influence of oxidative damage in the degenerative process of HSP.

Are serum nitric oxide and vascular endothelial growth factor levels affected by packed red blood cell transfusions?

BACKGROUND: Nitric oxide (NO) and vascular endothelial growth factor (VEGF) are important mediators for hemodynamics and angiogenesis in the body. NO coming from endothelial cells and red blood cells is particularly effective in hypoxic vasodilation. VEGF has known effects on the induction of NO synthesis and is also known to be affected by blood product transfusions. The objectives of this study were to measure NO and VEGF levels before and after packed red blood cell (PRBC) transfusions. STUDY DESIGN AND METHODS: Blood was drawn from preterm newborns before and 30 min after PRBC transfusions and samples were used for NO and VEGF measurements. NO end products nitrite and nitrate were measured by modified Greiss method, VEGF levels measured by double sandwitch ELISA method. Vital signs including heart rate and blood pressure were also recorded. RESULTS: Thirty four newborns were included in the study and overall 54 transfusion episodes were assessed for mediator levels. No difference was observed between the mediator levels before and after PRBC transfusions. Vital signs were also unchanged. CONCLUSION: As there was no change in NO end product levels with PRBC transfusions, it might suggest that hypoxia was not severe enough to cause nitrite increase; however, other NO sources might still be active. VEGF levels were found to be unchanged and may reflect a delayed effect of transfusion on VEGF induction.

Prevention of doxorubicin-induced cardiotoxicity by melatonin.

Anthracyclines, such as doxorubicin and daunorubicin, are highly effective anticancer agents. Cardiotoxicity made by these agents develops as a complication of the cancer chemotherapy. Melatonin, the chief secretory product of the pineal gland, was recently found to be a free radical scavenger and antioxidant. We decided to evaluate the tissue-protective effect of melatonin against myocardial toxic effects of doxorubicin in six groups of rats. Rats were given doxorubicin (Dx) (45 mg/kg dose) and melatonin (MEL) (10 mg/kg), first doxorubicin and then melatonin (DM), first melatonin and then doxorubicin (MD). The degree of cardiac muscle cell alterations were examined either histologically (mean total score technique) or biochemically. In doxorubicin-treated group, malondialdehyde (MDA) levels of the heart tissue were significantly increased, glutathione (GSH) levels were decreased compared to the control rats. In the group in which first doxorubicin and then melatonin was given, MDA levels were significantly decreased and glutathione (GSH) levels were increased compared to the doxorubicin-treated group. During ultrastructural analysis, in doxorubicin-treated group, cellular edema, mitochondrial deformation, decreased glycogen stores, and disordered myofibrillary structure were observed. In contrast, in first doxorubicin and then melatonin-treated group, normal cellular structure was observed. But, first melatonin and then doxorubicin-treated group was not significantly preserved from the doxorubicin-induced changes. By preventing lipid peroxidation and myocardial lesions, melatonin may be highly effective in protecting against doxorubicin-induced cardiotoxicity.

Effect of montelukast on symptoms and exhaled nitric oxide levels in 7- to 14-year-old children with seasonal allergic rhinitis.

BACKGROUND: Cysteinyl leukotrienes have been found to exert potent inflammatory effects in the upper airways and play a fundamental role in the pathogenesis of allergic rhinitis. Previous studies have reported increased levels of exhaled nitric oxide (eNO) in patients with allergic rhinitis without asthma symptoms. OBJECTIVE: To investigate the role of treatment with montelukast on symptoms, eNO levels, and peripheral eosinophil counts of children with seasonal allergic rhinitis during pollen season. METHODS: A randomized, double-blind, parallel-group study performed between April and June 2005 in 57 children aged 7 to 14 years with seasonal allergic rhinitis was performed. The study comprised a 1-week screening period, a 1-week run-in period, and a 2-week treatment period with once daily montelukast, 5 mg, or matching placebo. RESULTS: No significant difference at baseline was found in symptom scores, eNO levels, and blood eosinophil counts between the treatment and placebo groups. After 2 weeks of montelukast treatment, improvements from the baseline in the daytime nasal, composite, and daytime eye symptoms scores were significantly greater in the montelukast group compared with the placebo group (P < .001, P < .001, and P < .01, respectively). A significant decrease was also found in eosinophil counts (P < .001) in the montelukast group compared with the placebo group after treatment. Montelukast treatment did not produce a significant effect on eNO levels compared with placebo (P = .96). CONCLUSION: Montelukast treatment provided significant improvement in symptoms and peripheral eosinophil counts of school-age children with seasonal allergic rhinitis; however, it did not show a significant effect on eNO levels.

Plasma and urine nitric oxide levels in healthy Turkish children.

Nitric oxide (NO) is an important messenger molecule with a wide range of actions in virtually all cell systems and organs. In kidneys it participates in glomerular and medullary hemodynamics, tubuloglomerular feed-back, renin secretion, and extracellular fluid balance. Although the role of NO in regulating renal function in adults is well-established, it has recently been suggested that NO has a more critical role in maintaining basal renal blood flow and glomerular filtration rate (GFR) in the developing kidney. NO is rapidly metabolized to the stable end products nitrite and nitrate, which are more slowly excreted into the urine. Thus these metabolites can be recommended as useful markers of endogenous NO synthase activity, despite limited data about age-related changes in in-vivo NO production. The aims of this study were to determine age-related normal reference values of serum and urinary NO metabolites and to assess the probable relationship between these metabolites and the GFR. Normal levels of NO end products in blood and urine of 296 healthy children (117 female, 179 male) between the ages of 0 and 16 were investigated, as was whether these values change with age. Serum and urinary nitrate levels did not differ according to sex. Serum nitrate levels are higher in younger children, especially in the newborn period, and decrease with age. Nitrate levels in urine are higher in younger children with a peak in infancy (1 month to 1 year) and decrease with age. It was demonstrated that this decrease in serum and urinary nitrate levels with age parallels the increase in GFR. In conclusion, urinary NO products may be an indirect marker of serum NO levels and NO might have an important regulatory function both in the maintenance of renal function and in the maturation of the developing kidneys.