Plasma Flow Rate Research Articles

Ozone oxidative post-conditioning in acute renal failure

The ischaemia-reperfusion process is largely mediated by reactive oxygen species. Taking into account that a transient and controlled administration of ozone is able to upregulate cellular antioxidant enzymes, a morphological, biochemical and functional renal study was performed in rats undergoing warm renal ischaemia. Rats were divided into four groups. All except the negative controls underwent 60 min' bilateral renal ischaemia followed by 10 days' reperfusion. The positive control group received no further treatment. The ozone group received an ozone/oxygen mixture (ozone dose 0.5 mg/kg) immediately after the ischaemia and daily for the 10 days' reperfusion; the oxygen group were given the same concentration of oxygen alone (13 mg/kg). Biochemical parameters fructosamine, phospholipase A2, catalase, superoxide dismutase and thiobarbituric acid reactive substances were measured, as well as renal plasma flow and glomerular filtration rate. Renal plasma flow and glomerular filtration rate decreased significantly in the positive controls and the oxygen group whereas values in the ozone group were similar to those in the negative control group. With respect to the biochemical parameters, ozone maintained a homeostasis redox, with significant increases in catalase and superoxide dismutase activities and similar values for phospholipase A2 and fructosamine compared with the negative control group. Fewer morphological alterations were seen in kidneys from the ozone group. No advantages were obtained in the positive control and oxygen groups. The protective effect of ozone may be explained by upregulation of the antioxidant defence system and beneficial effects on blood circulation and in oxygen metabolism. Ozone treatment may represent a therapeutic approach for minimising renal damage after transplantation.

Endothelial nitric oxide synthase: from structure to function in one aspartic substitution

Cherney and co-workers examine the functional phenotype of the G894T eNOS polymorphism in a selected group of apparently healthy subjects. The investigators used L-arginine infusion and induced changes in renal hemodynamics. While L-arginine increased effective plasma flow and glomerular filtration rate in GG subjects, these responses were blunted in GT/TT subjects, suggesting that either the G894T polymorphism impairs eNOS function, or GG subjects exhibit augmented eNOS responsiveness to L-arginine. The complexity of this seemingly straightforward conclusion deserves elaboration.

How advanced aging influences clinical laboratory results

During normal aging, the biological structural changes merely narrow: the functional capacity, the residual homeostasis, is sufficient for a healthy lifestyle. Changes in elderly patients are generally poor symptoms, and clinical laboratory diagnoses are therefore of great importance. The aim of the author is to present age-dependent changes in some of the more important laboratory parameters. The levels of some compounds tend to rise, e.g., leptin, glucose, homocysteine, prostate-specific antigen, sex hormone binding-globulin, atrial natriuretic peptide, etc. This may be explained not only by enhanced production, but also by enhanced breakdown and excretion; the levels of other compounds may remain relatively constant, e.g., IgA, IgG, prolactin, the blood pH, etc.; and the levels of yet others may by decreased, e.g., albumin, total body calcium, phosphorus, iron, potassium, creatinine in the urine, renal plasma flow and glomerular filtration rate, vitamin D, oestrogen, aldosterone, testosterone, dehydroepiandrosterone and sulfate, etc. There are also differences (can be marked) between men and women (sex-related), and genetic influences. The author considers that, instead of cross-sectional analyses, it would be more correct to carry out longitudinal analyses in investigations of state among the elderly.

Evaluation of surface and bonding properties of cold rolled steel sheet pretreated by Ar/O 2 atmospheric pressure plasma at room temperature

In this study, cold rolled steel sheet for automotive was pretreated by the Ar/O 2 atmospheric pressure plasma at room temperature to improve the adhesive bonding properties. Through the analysis of contact angle and calculation of work of adhesion, the change of surface properties related to the plasma power, treatment time, and flow rate of O 2 gas were investigated before and after plasma treatment. Contact angle was degreased and work of adhesion was increased after plasma treatment. Meanwhile, the changes of surface roughness and morphology were observed by atomic force microscopy (AFM). And the chemical compositions of the steel sheet before and after plasma treatment were characterized by X-ray photoelectron spectroscopy (XPS). Surface roughness was slightly changed and new functional group, oxides, appeared on the surface of steel sheet after plasma treatment. Based on design of experiments and artificial neural network (ANN), the single lap shear test was performed to analyze the effect of plasma treatment parameters gas on adhesive bonding strength. From the result of the single lap shear test, the adhesive bonding strength of joint which was treated by Ar/O 2 atmospheric pressure plasma was improved about 23% compared with that of untreated sheet.

Numerical analysis for effect of process parameters of low-current micro-PAW on constricted arc

A model was put forward to simulate the electromagnetic phenomena and fluid field in plasma arc occurring during the low-current microplasma arc welding (low-current micro-PAW) process. The effects of the nozzle neck-in and welding current of micro-plasma arc on the arc electromagnetic field distribution were discussed. Finally, under the condition of different welding current, welding voltage, arc length, shield gas flow rate, and plasma flow rate, welding experiments of image sampling were carried out. Three types of microplasma arc, namely, needle plasma arc, columnar plasma arc, and opening model plasma arc, are founded by experiment. Based on the unified model, a thorough investigation of the low-current microplasma arc characteristics during the micro-PAW process was conducted. It was found that the process parameters have significant effects on the microplasma arc and the distributions of current density and electromagnet force distribution.

Effect of sodium overload on renal function of offspring from diabetic mothers

The aim if this study was to evaluate the effect of sodium overload on blood pressure and renal function in the offspring of diabetic rat mothers. Diabetes was induced with a single dose of streptozotocin before mating. Experimental groups were control (C), offspring from diabetic mother (D), control with sodium chloride (NaCl) overload (CS), and offspring from diabetic mother submitted to NaCl overload (DS). After weaning, all groups received food ad libitum; groups C and D had water ad libitum, and CS and DS received NaCl 0.15 M as drinking water. Renal morphology and function were evaluated in 3-month-old rats. Glomerular area, macrophage infiltration, interlobular artery wall thickness, and renal vascular resistance were significantly increased in CS, D, and DS compared with C. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were decreased in CS and D compared with C. In DS, GFR and fractional filtration were increased, suggesting a state of hyperfiltration. Hypertension was observed in groups D, CS, and DS from 2 months on and was more severe in DS. Our data suggest that diabetes during intrauterine development and salt overload beginning at an early age can cause hypertension and renal injury. When these conditions were associated, morphological and functional changes were much more intense, suggesting acceleration in the process of kidney injury.

Electrical, structural, and chemical properties of HfO2 films formed by electron beam evaporation

High dielectric constant hafnium oxide films were formed by electron beam (e-beam) evaporation on HF last terminated silicon (100) wafers. We report on the influence of low energy argon plasma (∼70 eV) and oxygen flow rate on the electrical, chemical, and structural properties of metal-insulator-silicon structures incorporating these e-beam deposited HfO2 films. The use of the film-densifying low energy argon plasma during the deposition results in an increase in the equivalent oxide thickness (EOT) values. We employ high resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy (XPS), and medium energy ion scattering experiments to investigate and understand the mechanisms leading to the EOT increase. We demonstrate very good agreement between the interfacial silicon oxide thicknesses derived independently from XPS and HRTEM measurements. We find that the e-beam evaporation technique enabled us to control the SiOx interfacial layer thickness down to ∼6 Å. Very low leakage current density (<10−4 A/cm2) is measured at flatband voltage +1 V into accumulation for an estimated EOT of 10.9±0.1 Å. Based on a combined HRTEM and capacitance-voltage (CV) analysis, employing a quantum-mechanical CV fitting procedure, we determine the dielectric constant (k) of HfO2 films, and associated interfacial SiOx layers, formed under various processing conditions. The k values are found to be 21.2 for HfO2 and 6.3 for the thinnest (∼6 Å) SiOx interfacial layer. The cross-wafer variations in the physical and electrical properties of the HfO2 films are presented.

Hypertriglyceridemia Induced Severe Pancreatitis with Multi System Organ Failure

Purpose: Introduction: Hypertriglyceridemia is a well known cause of pancreatitis. Serum triglyceride (TG) values above 1000 mg/dl can precipitate acute pancreatitis. Reduction of TG level below 1000 mg/dl prevents further episodes of pancreatitis. Diet restriction and fibric acid derivatives is the mainstay of treatment modalities. The role of plasmapheresis is controversial, mainly because of limited experience. Methods: Case Report: A 25 y/o Hispanic woman with no significant past medical history presented to ED with severe pain in abdomen, nausea and vomiting. Upon examination, she was in distress, afebrile and had tenderness in epigastric region with no evidence of xanthelesema or eruptive xanthomas. Laboratory analysis revealed a lipemic sample, markedly elevated TG 9720, and undeterminable other lipid fractions. WBC was 16.1 and Lipase 763. She was started on an Insulin drip to stimulate her lipoprotein lipase for her hypertriglyceridemia. Aggressive fluid management, analgesics, imipenem-cilastin were started and she was admitted to the ICU. CT abdomen showed normal GB, severe pancreatitis without necrosis and small bowel ileus. Over the next 24 hours, her condition deteriorated with worsening of abdominal pain, respiratory distress and anuria. Results: Subsequently she was intubated and placed on mechanical ventilation. The patient underwent plasmapheresis within 36 hours, and TG level remarkably decreased to 306. Her hospital stay was complicated by Multi System Organ Failure including acute renal failure requiring hemodialysis, mechanical ventilation, tracheostomy and intraabdominal abscesses. Plasmapheresis played a pivotal role in improving her clinical as well as laboratory condition. Patient was discharged home on fenofibrate, metformin and followed as outpatient. Conclusion: Discussion: Treatment of hypertriglyceridemia induced pancreatitis includes nil per oral, insulin drip (with or without heparin) and plasmapheresis. Plasmapheresis is an emerging method of decreasing the toxic chylomicron fraction, trigyceride and plasma proteases. It improves blood and plasma flow rates and perfusion to vital organs and also helps to avoid pseudo lab value which could be misleading in patient management. There has been no independent study to prove the effectiveness of plasmapheresis. Most of the data is extracted from case reports. Piolot et al reported successful use of plasmapheresis, which reduced the levels of TGs by 65–70%. In one case report, the outcome after plasmapheresis was dependent on the timing of its initiation. Our case thus emphasizes the importance of plasmapheresis for hypertriglyceridemia induced pancreatitis and emphasizes the need for randomized controlled trials evaluating its timing and use.

Misoprostol Effects on Diclofenac‐Induced Cardiorenal Changes in Salt‐Sensitive Patients with Hypertension: The MEDIC Study

To determine whether coadministration of misoprostol with the nonsteroidal antiinflammatory drug diclofenac lessens the increase in blood pressure and improves the alterations in renal hemodynamics induced by diclofenac. Prospective, randomized, double-blind, placebo-controlled, crossover study. Two university research centers. Nineteen senior (mean age 62 yrs [range 55-73 yrs]), salt-sensitive patients with stage 1 or 2 hypertension. After a 3-week antihypertensive withdrawal lead-in phase, patients received either diclofenac 75 mg alone or diclofenac 75 mg plus misoprostol 200 microg twice/day for 14 days. After a 10-day washout period, patients received the alternate treatment. Blood pressure was measured by 24-hour ambulatory blood pressure monitoring, effective renal plasma flow (ERPF) rate was determined by para-aminohippurate clearance, and glomerular filtration rate (GFR) was measured by iothalamate clearance. Mean arterial pressure (MAP = diastolic blood pressure + 0.33[systolic - diastolic blood pressure]) and rate-pressure product (RPP = systolic blood pressure x heart rate x 10(-2)) were also used to compare treatment groups. Diclofenac alone increased MAP by a mean +/- SEM of 5.0 +/- 1.0 mm Hg and RPP by 337 +/- 181 units compared with baseline. The ERPF rate and GFR decreased by 40.5 +/- 26.9 ml/minute and 14.1 +/- 6.5 ml/minute, respectively. Diclofenac plus misoprostol decreased the diclofenac-induced increase in MAP by 3.3 +/- 1.0 mm Hg (95% confidence interval [CI] 1.1-5.3 mm Hg, p=0.004) and decreased the RPP by 724 +/- 238 units (95% CI 225-1223 units, p=0.007). The ERPF rate increased by 56.1 +/- 35.0 ml/minute (95% CI -24.7-137.0 ml/min, p=0.15) and GFR by 18.1 +/- 7.1 ml/minute (95% CI 1.9-34.5 ml/min, p=0.03). Diclofenac alone was relatively well tolerated; no adverse effects were reported with diclofenac plus misoprostol. In senior salt-sensitive patients with hypertension, coadministration of misoprostol with diclofenac attenuated the blood pressure elevation and renal vasoconstrictive effects of diclofenac and was well tolerated.

Association of ABCB1genetic variants with renal function in Africans and in Caucasians

BackgroundThe P-glycoprotein, encoded by the ABCB1 gene, is expressed in human endothelial and mesangial cells, which contribute to control renal plasma flow and glomerular filtration rate. We investigated the association of ABCB1 variants with renal function in African and Caucasian subjects.MethodsIn Africans (290 subjects from 62 pedigrees), we genotyped the 2677G>T and 3435 C>T ABCB1 polymorphisms. Glomerular filtration rate (GFR) was measured using inulin clearance and effective renal plasma flow (ERPF) using para-aminohippurate clearance. In Caucasians (5382 unrelated subjects), we analyzed 30 SNPs located within and around ABCB1, using data from the Affymetrix 500 K chip. GFR was estimated using the simplified Modification of the Diet in Renal Disease (MDRD) and Cockcroft-Gault equations.ResultsIn Africans, compared to the reference genotype (GG or CC), each copy of the 2677T and 3435T allele was associated, respectively, with: GFR higher by 10.6 ± 2.9 (P < 0.001) and 4.4 ± 2.3 (P = 0.06) mL/min; ERPF higher by 47.5 ± 11.6 (P < 0.001) and 28.1 ± 10.5 (P = 0.007) mL/min; and renal resistances lower by 0.016 ± 0.004 (P < 0.001) and 0.011 ± 0.004 (P = 0.004) mm Hg/mL/min. In Caucasians, we identified 3 polymorphisms in the ABCB1 gene that were strongly associated with all estimates of GFR (smallest P value = 0.0006, overall P = 0.014 after multiple testing correction).ConclusionVariants of the ABCB1 gene were associated with renal function in both Africans and Caucasians and may therefore confer susceptibility to nephropathy in humans. If confirmed in other studies, these results point toward a new candidate gene for nephropathy in humans.

대기압 Ar/O2플라즈마 표면처리된 자동차용 냉연강판의 표면특성 및 접착특성평가

Cold rolled steel sheet for automotive was treated by Ar/ atmospheric pressure plasma to improve the adhesive bonding strength. Through the contact angle test and calculation of surface free energy for cold rolled steel sheet, the changes of surface properties were investigated before and after plasma treatment. The contact angle was decreased and surface free energy was increased after plasma treatment. And the change of surface roughness and morphology were observed by AFM(Atomic Force Microscope). The surface roughness of steel sheet was slightly changed. Based on Taguchi method, single lap shear test was performed to investigate the effect of experimental parameter such as plasma power, treatment time and flow rate of gas. Results shows that the bonding strength of steel sheet treated in Ar/ atmospheric pressure plasma was improved about 20% compared with untreated sheet.

Laser and plasma nitriding of titanium using CW-CO2 laser in the atmosphere

Surface nitriding of the titanium by the mixing technology with laser and plasma (LPN) in atmosphere has been investigated. Comparing with the technique of laser nitriding, we could obtain the titanium nitride at relatively low laser power density and the oxidation was prevented without the chamber. The synthesized layers comprised of titanium nitrides were about 178 μm depth. The effect of the laser power density, scanning velocity, and plasma flow rate on the components consisting of the material of the nitrided layer was studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to reveal the components consisting of the material of the nitrided layer.

Expression and role of connexins in the rat renal vasculature

Gap junctions are present in the juxtaglomerular apparatus enabling intercellular communication. Our study determined the location of different connexin subtypes within the juxtaglomerular apparatus of the rat, and the role of these subtypes in renal hemodynamics through the use of specific mimetic peptides. Immunohistochemical analysis showed connexins 37 and 40 expression in the endothelial and renin-secreting cells of the afferent arteriole, while connexin 40 was also found in extra- and intraglomerular mesangial cells. In contrast, connexin 43 was weakly expressed in endothelial cells of the afferent arteriole and within the glomerulus. Intra-renal infusion of the peptides (GAP) reported to block specific gap junctions ((Cx37,43)GAP27 or (Cx40)GAP27), elevated blood pressure, plasma renin activity, and angiotensin II levels, while decreasing renal plasma flow without a significant change in the glomerular filtration rate. Subsequent restoration of blood pressure reduced both renal plasma flow and glomerular filtration rate. In contrast, (Cx43)GAP26 reduced glomerular filtration rate without alterations in blood pressure, renal plasma flow, plasma renin activity, or angiotensin II levels. Hence, connexins 37 and 40 are expressed in the rat juxtaglomerular apparatus and these proteins control, in part, the renin-angiotensin system and renal autoregulation.

Effects of Electrical Stimulation of the Superior Ovarian Nerve and the Ovarian Plexus Nerve on the Ovarian Estradiol Secretion Rate in Rats

The present experiments examined the effects of electrical stimulation of the superior ovarian nerve (SON) and the ovarian plexus nerve (OPN) on the ovarian estradiol secretion in rats. The rats were anesthetized on the day of estrus, and the ovarian venous blood was collected intermittently. The secretion rate of estradiol from the ovary was calculated from differences in the estradiol concentration between ovarian venous plasma and systemic arterial blood plasma, and from the flow rate of ovarian venous plasma. Either an SON or OPN, ipsilateral to the ovary from which ovarian venous blood was collected, was electrically stimulated at a supramaximal intensity for C-fibers. The secretion rate of estradiol was significantly decreased by 47 +/- 6% during SON stimulation, but it was not significantly changed during OPN stimulation. These results suggest that autonomic nerves, which reach the ovary via the SON, have an inhibitory role in ovarian estradiol secretion.

Sterilization Efficacy of Steam Plasma Flow at Atmospheric Pressure

Recently, it has bemome a social problem that the disease infection by the pathogenic micro-organism spreads all over the world. Therefore, it is expected to establish an advanced sterilization method which has the advantages of simple configuration and ability to operate at atmospheric pressure. We studied the sterilization effects of the steam plasma flow at atmospheric pressure on bacteria. We developed a plasma source of the steam plasma flow at atmospheric pressure in a quartz tube of 8 mm in diameter and clarified its plasma characteristics and sterilization efficacy against Geobacillus stearothermophilus. A flow rate of the steam plasma flow of atmospheric pressure in a tube is 8.1 L/min which equals to the velocity of 2.7 m/s. When the applied voltage was 13 kVpp and its frequency was 3 kHz, the discharge current of 62 mA and the discharge power of 30 W were observed. Under this condition, a good sterilization result of G. stearothermophilus was obtained for the sterilization time of 30 minutes.

Specific adsorption of the autoantibodies from rheumatoid arthritis patient plasma using histidine-containing affinity beads

Rheumatoid arthritis is characterized by chronic polyarthritis and destruction of multiple joints. In this study, poly(hydroxyethyl methacrylate-N-methacryloyl-(L-histidine)-methylester) (PHEMAH) beads were used in the removal of pathogenic antibodies from rheumatoid arthritis patient plasma in a packed bed column. PHEMAH beads, in the size range of 80–120 μm, were produced by suspension polymerization. The beads were contacted with blood in an in vitro system. Loss of blood cells and clotting times were followed. PHEMAH beads were characterized by scanning electron microscopy. We found that PHEMAH beads had a spherical shape and porous structure. Loss of cells in the blood contacting with PHEMAH beads was negligible. IgM-antibody adsorption capacity decreased significantly with the increase of the plasma flow-rate. With increasing IgM-antibody concentration, the amount of IgM-antibody adsorbed per unit mass increased and then reached saturation. Maximum IgM-antibody adsorption amount was 69.2 mg/g. IgM-antibody molecules could be repeatedly adsorbed and desorbed without noticeable loss in the IgM-antibody adsorption amount.

Application of CCD Cameras to Investigations of Mixing on Boundaries of a Thermal Plasma Jet

Mixing of a thermal plasma jet with the surrounding atmosphere was studied using two CCD cameras (PCO SensiCam) situated detecting simultaneously the radiation of argon and nitrogen. The evaluation of image differences between two records showed that the location of regions on plasma jet boundaries characterised by stronger nitrogen radiation changes with the plasma flow rate. Close-to-laminar flow results in a small mixing rate and consequently low nitrogen optical emission on plasma jet boundaries. The increase of the flow rate leads to the formation of a relatively thick and stable layer on the boundaries characterised by strong nitrogen radiation. Further enhancement of the flow rate results in the formation of unstable regions of excited nitrogen molecules moving along the jet.

Connexins 37 and 40 transduce purinergic signals mediating renal autoregulation

Our previous data indicated that various subtypes of connexin (Cx) were expressed in the juxtaglomerular apparatus. Experiments were performed to characterize the effects on renal autoregulation of specific mimetic peptides that inhibit these Cx subtypes in Wistar-Kyoto rats. Intrarenal infusion of (Cx37,43)GAP27 increased autoregulatory index of renal plasma flow (0.06 +/- 0.05 to 0.47 +/- 0.06, n = 6, P < 0.05) and glomerular filtration rate (GFR; 0.01 +/- 0.07 to 0.49 +/- 0.07, P < 0.05). The additional administration of 8-cyclopentyl- 1,3-dipropylxanthine (CPX) produced a further elevation of autoregulatory index of RPF (0.86 +/- 0.07, P < 0.05) and GFR (0.88 +/- 0.09, P < 0.05), compared with (Cx37,43)GAP27 alone. However, the addition of pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid (PPADS) to (Cx37,43)GAP27 did not. Combined treatment with CPX and PPADS markedly worsened autoregulatory index of RPF (0.04 +/- 0.10 to 0.81 +/- 0.06, n = 6 P < 0.01) and GFR (0.05 +/- 0.08 to 0.79 +/- 0.05, P < 0.01). (Cx40)GAP27 induced similar changes to (Cx37,43)GAP27. Renal autoregulation was preserved in the presence of (Cx43)GAP26. Our results indicate that the inhibition of gap junction impaired renal autoregulation. Furthermore, the present data provide evidence that both adenosine and purinergic receptors contribute to glomerular autoregulation. Finally, our findings suggest that gap junctions, at least in part, transduce purinergic signals mediating renal autoregulation.

Obesity and chronic kidney disease: therapeutic implications

Obesity has now reached epidemic proportions, with far-reaching healthcare and economic implications. Obesity has been associated with end-organ damage in several tissues including the kidney and is one of the most important modifiable and preventable causes of death. Insulin resistance and the compensatory hyperinsulinemia, oxidative stress and adipocytokines, among others, have been implicated in the causation of obesity-related kidney damage. Obesity-related focal glomerulosclerosis is now a well recognized distinct histopathological entity and its pathophysiology has been related to the ‘hyperfiltration’ mechanism associated with increased renal plasma flow and glomerular filtration rate. This review will discuss the epidemiology and pathophysiology of obesity-related kidney damage with special focus on the central role of insulin resistance/hyperinsulinemia, adipocytokines and oxidative stress, as well as summarize the current evidence and recommendations in the management of this condition.

The effect of oral contraceptives on the nitric oxide system and renal function

We have demonstrated that oral contraceptive (OC) users exhibit elevated angiotensin II levels and angiotensin II type 1 receptor expression, indicative of renin-angiotensin system (RAS) activation, yet the renal and systemic consequences are minimal, suggesting that there is increased vasodilatory activity, counteracting the effect of RAS activation. We hypothesized that the nitric oxide (NO) system would be upregulated in OC users and that this would be reflected by a blunted hemodynamic response to l-arginine infusion. All subjects were studied after a 7-day controlled sodium and protein diet. Inulin and para-aminohippurate clearance techniques were used to assess renal function. l-Arginine was infused at 100, 250, and 500 mg/kg, each over 30 min. Skin endothelial NO synthase mRNA expression was assessed by real-time PCR. While OC nonusers exhibited significant increases in effective renal plasma flow (670.8 +/- 35.6 to 816.2 +/- 59.7 ml.min(-1).1.73 m(-2)) and glomerular filtration rate (133.4 +/- 4.3 to 151.0 +/- 5.7 ml.min(-1).1.73 m(-2), P = 0.04) and declines in renal vascular resistance (81.1 +/- 6.1 to 63.5 +/- 6.2 mmHg.ml(-1).min, P = 0.001) at the lower l-arginine infusion rates, the responses in OC users were blunted. While l-arginine reduced mean arterial pressure at the 250 and 500 mg/kg doses in OC nonusers, OC users only exhibited a decrease in mean arterial pressure at the highest infusion rate. In contrast, tissue endothelial NO synthase mRNA levels were higher in the OC users (P = 0.04). In summary, these findings suggest that the NO system is upregulated by OC use in young, healthy women. Increased activity of the NO pathway may modulate the hemodynamic effects of RAS activation in OC users.