Activity Of NO System Research Articles

Cardiac morphological and functional changes induced by C-type natriuretic peptide are different in normotensive and spontaneously hypertensive rats.

Inflammation and fibrosis are key mechanisms in cardiovascular remodeling. C-type natriuretic peptide (CNP) is an endothelium-derived factor with a cardiovascular protective role, although its in-vivo effect on cardiac remodeling linked to hypertension has not been investigated. The aim of this study was to determine the effects of chronic administration of CNP on inflammatory and fibrotic cardiac mechanisms in normotensive Wistar rats and spontaneously hypertensive rats (SHR). Twelve-week-old male SHR and normotensive rats were infused with CNP (0.75 μg/h/100 g) or isotonic saline (NaCl 0.9%) for 14 days (subcutaneous micro-osmotic pumps). Echocardiograms and electrocardiograms were performed, and SBP was measured. After treatment, transforming growth factor-beta 1, Smad proteins, tumor necrosis factor-alpha, interleukin-1 and interleukin-6, nitric oxide (NO) system and 2-thiobarbituric acid-reactive substances were evaluated in left ventricle. Histological studies were also performed. SHR showed lower cardiac output with signs of fibrosis and hypertrophy in left ventricle, higher NO-system activity and more oxidative damage, as well as higher pro-inflammatory and pro-fibrotic markers than normotensive rats. Chronic CNP treatment-attenuated hypertension and ventricular hypertrophy in SHR, with no changes in normotensive rats. In left ventricle, CNP induced an anti-inflammatory and antifibrotic response, decreasing both pro-fibrotic and pro-inflammatory cytokines in SHR. In addition, CNP reduced oxidative damage as well as collagen content, and upregulated the NO system in both groups. Chronic CNP treatment appears to attenuate hypertension and associated end-organ damage in the heart by reducing inflammation and fibrosis.

DYNAMICS OF CONCENTRATIONS OF NO-SYSTEM COMPONENTS DURING B16/F10 MELANOMA GROWTH IN FEMALE MICE WITH CHRONIC NEUROGENIC PAIN

Since chronic neurogenic pain has been reported to affect biological characteristics of B16/F10 melanoma, the purpose of the study was to analyze concentrations of components of the NO-system in mice during the growth of transplantable B16/F10 melanoma combined with chronic neurogenic pain. Methods. The study included 64 female mice. Melanoma was transplanted under the skin of the back to animals of the main group 2 weeks after the bilateral sciatic nerve ligation. Levels of NOS-3, NOS-2, endothelin-1, L-arginine, citrulline, total nitrite and ADMA were determined by ELISA in the intact skin and in tumor tissues. Results. The study showed that the dynamics of the studied parameters differed in tumor growth alone and in combination with chronic pain. Stably increased levels of NO-synthases in the tumor and stably increased ADMA levels with their decrease by week 3 of the growth were registered in the tumor growth with pain. Conclusions. Chronic pain probably contributes to the development of immunological tolerance to tumor antigens in the skin. Conditions are formed that facilitate the survival of tumor cells and contribute to the further development of melanoma. The dynamics of the NO-system activity can stimulate neoangiogenesis and enhance tumor invasion. Changes in the ADMA inhibitor levels in the tumor growth combined with chronic pain may indicate the control of NO levels through the metabolic regulation of NO-synthase activity, thus providing increased melanoma invasiveness.

115. Significance of systemic vascular disorders in gestational complications in pregnancy

Many pathogenetic similar disorders of pregnancy, including preeclampsia, placenta abruption, pregnancy losses, have been attributed, at least in part, to defects in the tightly regulated systemic vascular changes necessary to support a healthy pregnancy. Evaluation of the levels of endogenous regulators makes it possible to determine the risk of the realization of these pathological conditions from the early stages of pregnancy. Study objective To evaluate the role of endogenous regulators of angiogenesis in the development of recurrent miscarriage and preeclampsia. Methods Immunological and biochemical study of peripheral blood of pregnant women divided into three groups: 43 patients with recurrent pregnancy losses, 46 – with preeclampsia and 34 women of the control group. To explore the plasma levels of endothelin-1, VEGF and PlGF and activity of NO system we studied the angiogenesis process. Results The level of endothelin-1, in women with recurrent miscarriage and with preeclampsia, were significantly higher in both groups by 2.2 and 1.8 times (p Conclusions The pathogenetic mechanisms of development of preeclampsia and reproductive losses are associated with a violation of the functional state of the endothelium and the inferiority of the processes of angiogenesis.

BPC 157 antagonized the general anaesthetic potency of thiopental and reduced prolongation of anaesthesia induced by L-NAME/thiopental combination.

We hypothesized that certain effects of the general anaesthetic thiopental are dependent on NO-related mechanisms, which were consequently counteracted by stable gastric pentadecapeptide BPC 157. (1) All rats intraperitoneally received thiopental (20, 30, 40, and 50 mg/kg) while medication BPC 157 (10 μg/kg, 10 ng/kg, and 10 pg/kg) was given intraperitoneally at 5 min before thiopental. (2) To determine NO-related mechanisms, all rats received intraperitoneally thiopental 40 mg/kg while BPC 157 (10 μg/kg), L-NAME (10 mg/kg) and L-arginine (30 mg/kg) were applied alone and/or combined. BPC 157 was given at 25 min before thiopental while L-NAME, L-arginine, alone and/or combined, were applied at 20 min before thiopental. (1) BPC 157 own effect on thiopental anaesthesia: BPC 157 (10 ng/kg and 10 μg/kg) caused a significant antagonism of general anaesthesia produced by thiopental with a parallel shift of the dose-response curve to the right. (2) L-NAME-L-arginine-BPC 157 interrelations: L-NAME: Thiopental-induced anaesthesia duration was tripled. L-arginine: Usual thiopental anaesthesia time was not influenced. Active only when given with L-NAME or BPC 157: potentiating effects of L-NAME were lessened, not abolished; shortening effect of BPC 157: abolished. BPC 157 and L-NAME: Potentiating effects of L-NAME were abolished. BPC 157 and L-NAME and L-arginine: BPC 157 +L-NAME +L-arginine rats exhibited values close to those in BPC 157 rats. Thiopental general anaesthesia is simultaneously manipulated in both ways with NO system activity modulation, L-NAME (prolongation) and BPC 157 (shortening/counteraction) and L-arginine (interference with L-NAME and BPC 157).

Chronic treatment with atrial natriuretic peptide in spontaneously hypertensive rats: beneficial renal effects and sex differences.

ObjectiveThe aim of this study was to investigate the effects of chronic treatment with atrial natriuretic peptide (ANP) on renal function, nitric oxide (NO) system, oxidative stress, collagen content and apoptosis in kidneys of spontaneously hypertensive rats (SHR), as well as sex-related differences in the response to the treatment.Methods10 week-old male and female SHR were infused with ANP (100 ng/h/rat) or saline (NaCl 0.9%) for 14 days (subcutaneous osmotic pumps). Systolic blood pressure (SBP) was recorded and diuresis and natriuresis were determined. After treatment, renal NO synthase (NOS) activity and eNOS expression were evaluated. Thiobarbituric acid-reactive substances (TBARS), glutathione concentration and glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were determined in the kidney. Collagen was identified in renal slices by Sirius red staining and apoptosis by Tunel assay.ResultsFemale SHR showed lower SBP, oxidative stress, collagen content and apoptosis in kidney, and higher renal NOS activity and eNOS protein content, than males. ANP lowered SBP, increased diuresis, natriuresis, renal NOS activity and eNOS expression in both sexes. Renal response to ANP was more marked in females than in males. In kidney, ANP reduced TBARS, renal collagen content and apoptosis, and increased glutathione concentration and activity of GPx and SOD enzymes in both sexes.ConclusionsFemale SHR exhibited less organ damage than males. Chronic ANP treatment would ameliorate hypertension and end-organ damage in the kidney by reducing oxidative stress, increasing NO-system activity, and diminishing collagen content and apoptosis, in both sexes.

Involvement of nitric oxide and caveolins in the age-associated functional and structural changes in a heart under osmotic stress

Previous work done in our laboratory showed that water restriction during 24 and 72h induced changes in cardiovascular NOS activity without altering NOS protein levels in young and adult animals. These findings indicate that the involvement of NO in the regulatory mechanisms during dehydration depends on the magnitude of the water restriction and on age. Our aim was to study whether a controlled water restriction of 1 month affects cardiac function, NO synthase (NOS) activity and NOS, and cav-1 and -3 protein levels in rats during aging. Male Sprague-Dawley rats aged 2 and 16 months were divided into 2 groups: (CR) control restriction (WR) water restriction. Measurements of arterial blood pressure, heart rate, oxidative stress, NOS activity and NOS/cav-1 and -3 protein levels were performed. Cardiac function was evaluated by echocardiography. The results showed that adult rats have greater ESV, EDV and SV than young rats with similar SBP. Decreased atria NOS activity was caused by a reduction in NOS protein levels. Adult animals showed increased cav-1. Water restriction decreased NOS activity in young and adult rats associated to an increased cav-1. TBARS levels increased in adult animals. Higher ventricular NOS activity in adulthood would be caused by a reduction in both cav. Water restriction reduced NOS activity and increased cav in both age groups. In conclusion, our results indicated that dehydration modifies cardiac NO system activity and its regulatory proteins cav in order to maintain physiological cardiac function. Functional alterations are induced by the aging process as well as hypovolemic state.

BPC 157 antagonized the general anesthetic potency of thiopental and reduced prolongation of anesthesia time induced by L‐NAME/thiopental combination (1061.3)

We hypothesized the general anesthetic thiopental effect depending on NO‐related mechanisms, consequently counteracted by stable gastric pentadecapeptide BPC 157.(i) To determine the general anesthetic effect of thiopental and possible counteraction depending on BPC 157 administration, all rats received intraperitoneally thiopental (20, 30, 40 mg/kg) while medication (BPC 157 (10 μg/kg, 10 ng/kg, 10 pg/kg) was given intraperitoneally at 5 min before thiopental. (ii) To determine NO‐related mechanisms, all rats received intraperitoneally thiopental 40 mg/kg while BPC 157 (10 μg/kg), L‐NAME (10 mg/kg), L‐arginine (30 mg/kg) were applied alone and/or combined. BPC 157 was given at 25 min before thiopental while L‐NAME, L‐arginine, alone and/or combined, were applied at 20 min before thiopental.(i) BPC 157 (10 ng/kg and 10 μg/kg), caused significant antagonism of general anesthesia produced by thiopental with a parallel shift of the dose‐response curve to the right. (ii) L‐NAME. Thiopental‐induced anesthesia duration was tripled. L‐arginine. Active only given with L‐NAME or BPC 157: habitual thiopental anesthesia time not influenced; potentiating effects of L‐NAME lessened, not abolished; shortening effect of BPC 157: abolished. BPC 157 and L‐NAME. Potentiating effects of L‐NAME was abolished. L‐NAME and L‐arginine and BPC 157. L‐NAME+L‐arginine+BPC 157 rats exhibited values close to those in BPC 157 rats.Thiopental general anaesthesia is simultaneously manipulated in both ways with NO‐system activity modulation, L‐NAME (prolongation) and BPC 157 (shortening/counteraction). BPC 157 and L‐arginine might serve two NO‐system pathways, more or less active, alternatively activated.Grant Funding Source: Supported by Grant 108‐ 1083570‐3635, Croatia

The role of DDAH2/NOS/NO in lung endothelial cell damages in streptozotocin induced diabetic rats with sepsis

Objective To investigate the pulmonary microvascular responsiveness of diabetic animals to sepsis and the potential mechanism of NO system.Methods Sixty-four Wistar rats of clean grade were randomly (random number) divided into 4 groups,namely normal control group (group A,n =16),diabetes group (group B,n =16),sepsis group (group C,n =16),diabetes and sepsis group (group D,n =16).Diabetic mellitus model was made in rats with injection of streptozotocin,STZ (65 mg/kg).Successful model was defined as the blood glucose value≥ 16.67 mmol/L 48 hours after injection of STZ.All animals were fed 4 weeks before initiation of next experiment.The sepsis model was established by intravenous injection of LPS (10 mg/kg) in rats.RT-PCR was used to determine the mRNA expression of Tie-2 in rats'blood.The ratio of dry/wet of lung tissue and the extravasation of Evans blue dye into the lung were detected.Quantitation of NO in lung tissue and serum was measured by using Griess method.RT-PCR was also used for determination of iNOS,eNOS,DDAH2 mRNA expressions in lung tissue.Data were analyzed with ANONA and LSD method for comparison between groups,and P ＜ 0.05 was considered statistically significant.Results Compared with septic group.,the diabetic rats with sepsis group demonstrated higher expression of Tie-2 mRNA in blood (19.72 ± 0.70) vs.(3.99 ± 0.92),P =0.00,lower ratio of dry/wet in lung tissue (0.19 ±0.01) vs.(0.22 ±0.01),P =0.000,higher permeability of Evans blue dye into lung tissue (3.76 ± 0.77) vs.(1.74 ± 0.24),P =0.000.Serum NO level was lower in group D than that in group C (123.13 ±4.24) vs.(188.30 ±5.18),P =0.000,however,NO levels in lung tissue of both group D and group C were higher than that in control group (53.62 ± 6.70),(23.63± 3.92) vs.(10.37 ± 1.29),P =0.00,and NO level in group D was higher in 2 times than that in group C (P =0.00).However,there were no differences in eNOS expression among groups A,B and C,but the difference in eNOS expression was present between group D with lower expression and group A,that lower in group D (0.07 ±0.02) vs.(0.38 ±0.05),P=0.017.Compared with group C,the expression of iNOS was higher in group D (80.23 ±2.49),(32.48±5.37) vs.(1.74±0.23),P=0.00),and the expression of DDAH2 was lower in group D (0.49 ±0.13),(7.26 ±0.50) vs.(11.96 ±0.55).Conclusions Diabetic rats with sepsis enhanced endothelial cell damages.Diabetes deteriorates the regulatory activity of NO system,suggesting the potential mechanism of the worsened damages of EC in diabetic sepsis host. Key words: Diabetes; Sepsis; Pulmonary microvascular endothelial; DDAH2; Asymmetric dimethylarginine ; NOS; NO; Endothelial cell injury

Sex Differences in the Beneficial Cardiac Effects of Chronic Treatment with Atrial Natriuretic Peptide In Spontaneously Hypertensive Rats

IntroductionThe aim of this study was to investigate both the effects of chronic treatment with atrial natriuretic peptide (ANP) on systolic blood pressure (SBP), cardiac nitric oxide (NO) system, oxidative stress, hypertrophy, fibrosis and apoptosis in spontaneously hypertensive rats (SHR), and sex-related differences in the response to the treatment.Methods10 week-old male and female SHR were infused with ANP (100 ng/hr/rat) or saline (NaCl 0.9%) for 14 days (subcutaneous osmotic pumps). SBP was recorded and nitrites and nitrates excretion (NOx) were determined. After treatment, NO synthase (NOS) activity, eNOS expression, thiobarbituric acid-reactive substances (TBARS) and glutathione concentration were determined in left ventricle, as well as the activity of glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD). Morphological studies in left ventricle were performed in slices stained with hematoxylin-eosin or Sirius red to identify collagen as a fibrosis indicator; immunohistochemistry was employed for identification of transforming growth factor beta; and apoptosis was evaluated by Tunel assay.ResultsFemale SHR showed lower SBP, higher NO-system activity and less oxidative stress, fibrosis and hypertrophy in left ventricle, as well as higher cardiac NOS activity, eNOS protein content and NOx excretion than male SHR. Although ANP treatment lowered blood pressure and increased NOS activity and eNOS expression in both sexes, cardiac NOS response to ANP was more marked in females. In left ventricle, ANP reduced TBARS and increased glutathione concentration and activity of CAT and SOD enzymes in both sexes, as well as GPx activity in males. ANP decreased fibrosis and apoptosis in hearts from male and female SHR but females showed less end-organ damage in heart. Chronic ANP treatment would ameliorate hypertension and end-organ damage in heart by reducing oxidative stress, increasing NO-system activity, and diminishing fibrosis and hypertrophy.

Role of Nitric Oxide in the Pathogenesis of Alloxan Diabetes

We studied the effects of N(w)-nitro-L-arginine (L-NNA), a nonselective inhibitor of NO synthases, on the severity of type 1 diabetes mellitus induced by subcutaneous injection of 130 mg/kg alloxan in August rats with high activity of NO system and in Wistar rats. Five days after alloxan injection, hyperglycemia levels after overnight fasting in August and Wistar rats were 27.1±3.7 and 22.0±1.1 mmol/liter, respectively (p<0.03). The mortality over 15 days after alloxan injection in August rats was higher than in Wistar rats (36 and 26%, respectively). L-NNA normalized glucose levels in diabetics of both groups. It completely prevented mortality in August and reduced it to 13% in Wistar rats. Body weight loss and polydipsia after L-NNA injection were also less pronounced in August rats. Plasma nitrite/nitrate concentrations in August rats were 32% higher than in Wistar rats, both in intact and diabetic rats. These data attest to an important role of NO in the pathogenesis of alloxan diabetes.

Fraction SX of Maitake Mushroom Favorably Influences Blood Glucose Levels and Blood Pressure in Streptozotocin-Induced Diabetic Rats

We assessed whether fraction SX derived from maitake mushroom could play a beneficial role in the treatment of a laboratory model of type-1 diabetes by decreasing circulating glucose levels and lowering blood pressure (BP). We injected 50 mg/kg body weight (BW) streptozotocin (STZ) intraperitoneally (i.p.) into 48 male Sprague-Dawley rats (SD) to produce a laboratory model of type-1 diabetes. SD were divided into four groups of 12 SD. A control group ate straight pulverized rat chow. To three treatment groups, we added into the pulverized rat chow: gliclazide (10 mg/kg), pioglitazone (10-30 mg/kg), or maitake SX (2.5 g/kg). In addition to measuring BW, circulating glucose level, and BP, the following procedures were also carried out: insulin challenge (insulin sensitivity), losartan challenge (renin-angiotensin system activity), Nw-nitro-L arginine-methyl ester hydrochloride (LNAME) challenge (nitric oxide [NO] system activity), and evaluation of serum angiotensin converting enzyme (ACE) activity. All treatments compared with control generally decreased circulating glucose levels, but only the maitake SX consistently enhanced measured insulin sensitivity. We found that maitake SX could significantly lower systolic blood pressure (SBP) in diabetic SD. In general, only SD receiving maitake SX, not the two drugs, showed decreased activity of the renin-angiotensin system and increased NO system activity compared with control under the conditions examined. Our results suggest that maitake SX may be useful for treating perturbations in glucose-insulin metabolism and elevated BP in type-1 diabetes.

1.009 NIGRAL IRON DEPOSITION OCCURS ACROSS MOTOR PHENOTYPIC EXPRESSIONS OF PARKINSON'S DISEASE

Currently, there are numerous data showing that free radicals may play an important role in the mechanisms of emergence and development of central nervous system diseases. Objective: To evaluate the activity of NO-system, depending on the stage of Parkinson’s disease. Methods: We examined 55 patients with PD (28 men and 27 women) aged 30 to 75 years. The functional state of NO-system was evaluated by changes in the level of content in erythrocyte membranes of stable metabolites of NO – NO2 and NO3, the activity of eNOS, NADPH-dependent nitrate reductase, the content of peroxynitrite (ONOO−). Results: Parameters of NO in the number of I-II-III stages of growing 23.01±0.425 – 27, 69±0.421 – 31, 77±0.745mmol/L, control (22.72±0.09). Indicator of eNOS is reduced in a number of I-II-III century (11.01±0.453; 9.35±0.144; 8.57±0.491mmol/min/l, the control group 13.9±0.423). NADPH-dependent nitrate reductase increased in the number of I-II-III stage (1.41±0.234; 1.6±0.523; 2.05±0.312mmol/min/l), control (1.02±0.234), the contents of peroxynitrite-ONOO±, was increased in parallel in a row I-II-III century. (0.21±0.213; 0.32±0.345; 0.43±0.153mmol/l) in control 0.08±0.223. Conclusion: The imbalance in the NO-system are most pronounced in patients in the developed stage of Parkinson’s disease and appears to play an important role in the pathogenesis of this disease.

Effects of cold stress on nitric oxide in duodenum of chicks

Animals may suffer from a variety of environmental stressors every day, among which is cold stress, which commonly exists in cold regions. The aim of this study was to investigate changes in antioxidative function and inducible nitric oxide synthase-nitric oxide (iNOS-NO) system activity in the duodenum of chicks as a reaction to cold stress. A total of 84 male chicks (15 d old) were randomly allocated to 12 groups (7 chickens/group). There were 1 control group and 5 treatment groups for acute cold stress and 3 control groups and 3 treatment groups for chronic cold stress. Antioxidative function was examined by superoxide dismutase (SOD), and oxidative damage was examined by malondialdehyde (MDA) detection. The iNOS-NO system activity was identified by NO content and NOS activity assay, and the transcription of iNOS mRNA was tested by fluorescence quantitative PCR. The results showed that under acute cold stress MDA level increased, the activity of NO in the duodenum fluctuated, and the activity of SOD and iNOS in the duodenum first increased and then decreased, whereas the expression of iNOS mRNA decreased. Under chronic cold stress the activity of SOD, NO, and NOS first decreased and then increased, whereas the MDA level and the expression of iNOS mRNA increased. The results indicated that both acute and chronic cold stress could cause duodenum oxidative stress and change in iNOS, which was related to the intestinal damage process.

Alterações vasculares em ratos obesos por dieta rica em gordura: papel da Via L-arginina/NO Endotelial

FUNDAMENTO: Mecanismos subjacentes a anormalidades vasculares na obesidade ainda não estão completamente esclarecidos. OBJETIVO: Foi avaliada a via do óxido nítrico/L-arginina na resposta vascular de ratos obesos por dieta rica em gordura, enfocando as células endoteliais e do músculo liso. MÉTODOS: Ratos com 30 dias de vida foram divididos em 2 grupos: controle (C) e obeso (OB, ratos sob dieta rica em gordura por 30 semanas). Após 30 semanas, foram registrados o peso corporal, índice de adiposidade, pressão arterial e perfis metabólicos e endócrinos dos animais. Foram obtidas curvas para noradrelanina na ausência e presença de inibidor de óxido nítrico sintase (L-NAME, 3x10-4M) em aorta torácica intacta e com desnudamento em ratos C e OB. RESULTADOS: As medidas de peso corporal, índice de adiposidade, leptina e insulina aumentaram nos ratos OB, enquanto a pressão arterial permaneceu inalterada. A obesidade também produziu tolerância à glicose e resistência à insulina. A reatividade à noradrenalina da aorta intacta foi similar em ratos C e OB. A presença de L-NAME produziu um aumento similar nas respostas máximas, mas um desvio maior à esquerda das respostas nas aortas intactas dos ratos C em relação aos ratos OB [EC50 (x10-7M): C = 1,84 (0,83-4,07), O = 2,49 (1,41-4,38); presença de L-NAME C = 0,02 (0,01-0,04)*, O = 0,21 (0,11-0,40)*†,*p < 0,05 vs controle respectivo,†p < 0,05 vs controle mais L-NAME, n = 6-7]. Nenhum dos protocolos alterou a reatividade à noradrenalina de aortas com desnudamento. CONCLUSÃO: A obesidade induzida por dieta rica em gordura promove alterações metabólicas e vasculares. A alteração vascular envolveu uma melhora da via endotelial L-arginina/NO provavelmente relacionada à hiperinsulinemia e hiperleptinemia induzidas por dieta. A maior resistência aos efeitos do L-NAME na aorta de ratos obesos diz respeito a menor vulnerabilidade de indivíduos obesos na presença de patologias associadas que causam danos à atividade do sistema NO.

Effect of Acute Alloxan Diabetes on Ischemic and Reperfusion Arrhythmias in Rats with Different Activity of Nitric Oxide System

Similar degree of glycemia (28-31 mmol/liter) and similar mortality (37-42%) were revealed in August rats exhibiting enhanced activity of NO system and in Wistar rats 3 weeks after alloxan treatment. Under conditions of myocardial ischemia caused by 10-min coronary artery ligation, the intensity of arrhythmias did not differ from the control in Wistar rats with diabetes mellitus and increased in August rats. Under conditions of reperfusion, diabetes produced an antiarrhythmic effect in Wistar rats and did not affect arrhythmia in August rats. Plasma concentrations of nitrates and nitrites in Wistar and August rats increased by 82 and 143%, respectively, compared to the control. The level of hemoxygenase-1 (hsp32) in the myocardium remained unchanged in Wistar rats and decreased by 26% in August rats. Thus, the absence of antiarrhythmic effect of acute diabetes in August rats is probably related to elevated NO content and reduced antioxidant activity.

Rat skeletal muscle contractility: The role of beta-adrenoceptors and nitric oxide system

Both beta-adrenoceptors and the nitric oxide system play a significant role in the modulation of skeletal muscle contractility. Skeletal muscle adrenoceptors mainly belong to beta2 subtype, while all three types of nitric oxide synthase may influence muscle contractility. The aim of our study was to investigate the possible interplay between beta-adrenoceptor agonists and nitric oxide system in the modulation of contractility of isolated rat hemidiaphragm. Adrenaline (0.05-1.5 μmol/L) and noradrenaline (1-5 μmol/L) given in a cumulative manner produced a concentration-related increase in Td. L-NAME (1, 3 and 10 mmol/L; 30 min of incubation) produced a significant, dose-dependent increase in Td of the muscle pretreated with cumulative concentrations of adrenaline (ΔTd up to 16%). When hemidiaphragm was pretreated with noradrenaline instead of adrenaline, L-NAME (3 mmol/L) it produced a similar potentiation of Td. In conclusion, nitric oxide seems to oppose beta-adrenoceptor potentiation of diaphragm contractility, and such an interaction depends on previous adrenoceptor stimulation. Nitric oxide probably decreases beta-adrenoceptor response via cGMP-induced stimulation of phosphodiesterase 2. The interaction between substances which modulate NO system activity and cAMP levels in the skeletal muscle may be of a great clinical importance for the treatment of certain respiratory and neurological diseases.

Stress-induced changes in the nitric oxide system of shore crabs living under different ecological conditions

The NO synthesis system in the brain and hemolymph of shore crabs Hemigrapsus sanguineus (Decapoda: Varunidae) living under different ecological conditions was examined under normal conditions and under acute stress. Intact crabs sampled from an area with a high anthropogenic load had a higher initial level of NO compared to crabs from a relatively clean location. After acute damaging exposure, the dynamics of the NO system activity in crabs from different stations differed markedly. The number of NO-positive elements in the brain and the level of NO metabolites in the hemolymph dramatically increased immediately after injuries in all groups of crabs. One hour after acute exposure, the expression of inducible NO-synthase in the protocerebral neurons was observed in crabs inhabiting the chronically polluted area. These results demonstrate for the first time the influence of pollution on the activity of NO-ergic processes and the involvement of nitric oxide in the formation of behavioral defense response in crustaceans under acute stress.

Exposure to zinc deficiency in fetal and postnatal life determines nitric oxide system activity and arterial blood pressure levels in adult rats

We had previously shown that prenatal exposure to Zn-deficient diets induces an increase in blood pressure and impairs renal function in adult rats. The aim of the present study was to investigate if moderate Zn restriction during early growth periods, fetal life and lactation would induce impairment in the vascular and renal NO system and alterations in plasma lipid profile. We also investigated if these effects persisted into adult life, even when a Zn-replete diet was provided after weaning. Pregnant rats were fed control (30 parts per million (ppm)) or low (8 ppm) Zn diets throughout gestation up to weaning. Afterwards, male offspring from low-Zn mothers were assigned to low- or control-Zn diets during 60 d. Male offspring from control mothers were fed a control diet. Animals exposed to Zn restriction showed low birth weight, increased systolic blood pressure and serum TAG levels, and decreased glomerular filtration rate in adulthood. Zn restriction induced a decrease in vascular and renal NO synthase activity and a reduced expression of the endothelial NO synthase isoform in aorta. A control-Zn diet during post-weaning growth returned TAG levels to normal but was unsuccessful in normalising systolic blood pressure, glomerular filtration rate or NO system activity in Zn-deficient offspring. Zn restriction during fetal life, lactation and/or post-weaning growth induced alterations in the vascular and renal NO system and in lipid metabolism that could contribute to the programming of hypertension and renal dysfunction in adulthood.

Effects of omega-3 PUFAs on activity of NO-system after myocardial ischemia/reperfusion

The most of eNOS protein is known to be localized in cell plasmatic membranes, especially in caveolae. However, effects of cell membrane modification on the activity of NO-system remain to a large extent unclear. This study was to determine if eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids influence NOS activity and NO production after their supplementation to the rat diet (4 weeks, 0.1 g/kg per day). An increased intake of omega-3 PUFAs resulted in an increase in EPA and DHA contents in the membranes of cardiomyocytes after isolated heart ischemia/reperfusion (1.8-fold and 3.5-fold, respectively). Levels of arachidonic acid (AA), production of LTC4 and TxA2 were reduced (2.1-fold, 3.0-fold and 1.8-fold, respectively). We have found that ischemia/reperfusion reduced a total NOS and eNOS activities (1.4-fold and 4.2-fold, respectively) and increased iNOS activity in cardiac tissue by 57%. Cell membrane modification by omega-3 PUFAs prevented both a decrease in the total activity of NOS and eNOS. It also limited an excessive activation of the iNOS, improved myocardial function, prevented vasoconstriction and reduced oxidative stress in the heart after ischemia/reperfusion. Our results suggest that cardioprotective effects of omega-3 PUFAs were realized through a decrease in AA content in cell membranes, potentiation of the protective function of eNOS and modulation of iNOS-derived NO release after ischemia/reperfusion.

EFFECT OF NITRIC OXIDE INHIBITION ON KIDNEY FUNCTION IN EXPERIMENTAL RENOVASCULAR HYPERTENSION

We examined the effect of acute systemic blockade of nitric oxide (N0) synthesis on blood pressure and renal function in rats with angiotensin II dependent two-kidney, one-clip Goldblatt hypertension. Hypertensive animals had significantly higher blood pressures, plasma NO metabolite concentrations and urinary NO metabolite excretion rates than control rats. Intravenous administration of NG-nitro-L-arginine methylester (L-NAME) (10 mg/kg) increased mean arterial pressure in both hypertensive and control animals with the magnitude of increase being greater in hypertensive than control rats (32±3 vs. 20±2 mmHg,p< 0.05). L-NAME did not affect glomerular filtration rates of normal and clipped kidneys but significantly decreased non-clipped kidney glomerular filtration rate (1.1±0.1 vs. 0.7±0.1 ml/min per g kidney wt, p< 0.05). Blood flow to normal and non-clipped kidneys fell in response to L-NAME. Percent reduction in renal blood flow produced by L-NAME was significantly greater in non-clipped than normal kidneys (38±3 vs. 24±2%,p< 0.05). In contrast, clipped kidney blood flow increased after L-NAME (3.3±0.2 vs. 4.0±0.2 ml/min per g kidney wt,p< 0.05). An identical improvement in clipped kidney blood flow occurred when arterial pressure was raised with aortic constriction indicating that the systemic pressor effect of L-NAME was responsible for this finding. These results indicate that NO plays an important role in systemic and non-clipped kidney hemodynamics in renovascular hypertension. Because NO has little influence on stenotic kidney function, the stimulus for increased NO system activity in this disease appears to be vascular shear stress rather than elevated circulating or intrarenal angiotensin II concentrations.