Evidence for the existence of two distinct functions for the inducible NO synthase in the rat kidney: effect of aminoguanidine in rats with 5/6 ablation

Exercise in Diabetic Nephropathy: Protective Effects and Molecular Mechanism

Diabetic nephropathy (DN) is a serious complication of diabetes, and its progression is influenced by factors like oxidative stress, inflammation, cell death, and fibrosis. Compared to drug treatment, exercise offers a cost-effective and low-risk approach to slowing down DN progression. Through multiple ways and mechanisms, exercise helps to control blood sugar and blood pressure and reduce serum creatinine and albuminuria, thereby alleviating kidney damage. This review explores the beneficial effects of exercise on DN improvement and highlights its potential mechanisms for ameliorating DN. In-depth understanding of the role and mechanism of exercise in improving DN would pave the way for formulating safe and effective exercise programs for the treatment and prevention of DN.

N-acetylcysteine protects against diabetic nephropathy through control of oxidative and nitrosative stress by recovery of nitric oxide in rats

The diabetes mellitus (DM) induces several changes, with substantial increase of reactive oxygen species (ROS). The ROS cause damage to systemic and renal microvasculature, which could be one of the mechanisms involved in the development of diabetic nephropathy (DN). The ROS modulate other substances like the nitric oxide (NO), a vasodilator with important role in the renal function. N-acetylcysteine (NAC) is an antioxidant that acts replenishing intracellular cysteine levels, which is essential for glutathione formation. The aim of this study was to evaluate the effect of early or late NAC treatment on oxidative/nitrosative stress in DN progression. All rats were submitted to unilateral nephrectomy and diabetes was induced with streptozotocin. The animals were allocated into six groups: controls that received water (CTL) or NAC (CTL + NAC); diabetic groups that received early or late, water (DM-E; DM-L) or NAC (DM + NAC-E; DM + NAC-L), started on 5th day (early) or 4th week (late) after diabetes induction, during 8 weeks. After NAC treatment, the rats were placed in individual metabolic cages to obtain urine and blood samples for analysis of metabolic profile, renal function, thiobarbituric acid reactive substances (TBARS) and NO. At the end of the protocol, the renal cortex was removed for TBARS, NOS evaluation, antioxidants markers and histology. The DM-E group compared to CTL showed a significant increase in glycemia and proteinuria and impaired renal function; there was a significant increase of TBARS in plasma, urine and renal tissue, and also a significant decrease in plasma NO, which were reverted after early NAC treatment. The eNOS was decreased and iNOS was increased in DM-E vs. CTL, p < 0.05. The early NAC treatment in DM rats reduced proteinuria, creatinine, urea, TBARS and iNOS and, increased creatinine clearance, NO and eNOS, increasing significantly the antioxidant defenses, promoting elevated catalase and glutathione compared to DM-E group, all p < 0.05. The late NAC treatment in diabetic rats vs.DM-E showed reduced proteinuria and TBARS excretion and higher values of creatinine clearance and NO, all statistically significant. Histological analysis of the animals in DM-E or DM-L showed significant tubular changes with degeneration and vacuolization in tubular cells, dilated tubular lumen, intense glycosidic degeneration, and discreet mesangial expansion with interstitial fibrosis area. The DM + NAC-E group showed moderate glycosidic degeneration, however, did not present tubular degeneration or fibrosis. The DM + NAC-L group showed severe glycosidic degeneration, moderate tubular cell degeneration, light and focal dilatation of the tubules, with no fibrosis. Our study showed that NAC protected the diabetic rats against renal injury, probably due to the control of oxidative stress via recovery of the NO bioavailability, showing that early NAC was more effective than late treatment. All these data suggest that NAC may be useful in the adjuvant treatment in a safe way, in the early phase of the disease. Eventually, prolonged treatment, even if it is started later, could change the natural history of the disease, delaying the complications of diabetes in renal tissue.

Antioxidant diet and sex interact to regulate NOS isoform expression and glomerular mesangium proliferation in Zucker diabetic rat kidney

Oxidative stress contributes substantially to the pathophysiology of diabetic nephropathy (DN). Consumption of an antioxidant-fortified (AO) diet from an early age prevents or delays later development of DN in the Zucker rat female with type 2 diabetes. We hypothesize this is due to effects on mesangial matrix and renal nitric oxide synthase (NOS) distribution and to sex-specific differences in NOS responses in the diabetic kidney. Total glomerular tuft area (GTA) and PAS-positive tuft area (PTA), endothelial (e), neuronal (n) and inducible (i) NOS were quantified in males and females on AO or regular (REG) diet at 6 and 20 weeks of age. eNOS was observed in glomeruli and tubules. nNOS predominantly localized to tubular epithelium in both cortex and medulla. iNOS was expressed in proximal and distal tubules and collecting ducts. Sex, diabetes duration and AO diet affected the distribution of the three isoforms. GTA and PTA increased with duration of hyperglycemia and showed a negative correlation with renal levels of all NOS isoforms. AO diet in both genders was associated with less PAS-positive staining and less mesangial expansion than the REG diet, an early increase in cortical iNOS in males, and sex-specific changes in cortical eNOS at 20 weeks. These effects of AO diet may contribute to sex-specific preservation of renal function in females.

Chronic Running Exercise Alleviates Early Progression of Nephropathy with Upregulation of Nitric Oxide Synthases and Suppression of Glycation in Zucker Diabetic Rats

Exercise training is known to exert multiple beneficial effects including renal protection in type 2 diabetes mellitus and obesity. However, the mechanisms regulating these actions remain unclear. The present study evaluated the effects of chronic running exercise on the early stage of diabetic nephropathy, focusing on nitric oxide synthase (NOS), oxidative stress and glycation in the kidneys of Zucker diabetic fatty (ZDF) rats. Male ZDF rats (6 weeks old) underwent forced treadmill exercise for 8 weeks (Ex-ZDF). Sedentary ZDF (Sed-ZDF) and Zucker lean (Sed-ZL) rats served as controls. Exercise attenuated hyperglycemia (plasma glucose; 242 ± 43 mg/dL in Sed-ZDF and 115 ± 5 mg/dL in Ex-ZDF) with increased insulin secretion (plasma insulin; 2.3 ± 0.7 and 5.3 ± 0.9 ng/mL), reduced albumin excretion (urine albumin; 492 ± 70 and 176 ± 11 mg/g creatinine) and normalized creatinine clearance (9.7 ± 1.4 and 4.5 ± 0.8 mL/min per body weight) in ZDF rats. Endothelial (e) and neuronal (n) NOS expression in kidneys of Sed-ZDF rats were lower compared with Sed-ZL rats (p<0.01), while both eNOS and nNOS expression were upregulated by exercise (p<0.01). Furthermore, exercise decreased NADPH oxidase activity, p47phox expression (p<0.01) and α-oxoaldehydes (the precursors for advanced glycation end products) (p<0.01) in the kidneys of ZDF rats. Additionally, morphometric evidence indicated renal damage was reduced in response to exercise. These data suggest that upregulation of NOS expression, suppression of NADPH oxidase and α-oxoaldehydes in the kidneys may, at least in part, contribute to the renal protective effects of exercise in the early progression of diabetic nephropathy in ZDF rats. Moreover, this study supports the theory that chronic aerobic exercise could be recommended as an effective non-pharmacological therapy for renoprotection in the early stages of type 2 diabetes mellitus and obesity.

Exercise training upregulates nitric oxide synthases in the kidney of rats with chronic heart failure

There is an interaction between heart and kidney diseases, which is a condition termed cardiorenal syndrome. Exercise training has cardioprotective effects, involving upregulation of endothelial (e) nitric oxide synthase (NOS) in the cardiovascular system. However, the effects of exercise training on NOS in the kidney with heart disease are unknown. The aim of the present study was to investigate whether exercise training upregulates NOS in the kidney, left ventricle and aorta of rats with chronic heart failure (CHF). Male Sprague-Dawley rats underwent left coronary artery ligation (LCAL) to induce CHF and were randomly assigned to sedentary or treadmill exercise groups 4 weeks after LCAL. Three days after exercising for 4 weeks, urine samples were collected for 24 h and blood samples were collected following decapitation. Nitric oxide synthase activity and protein expression were examined. Significant interactions between CHF and exercise training were observed on parameters of cardiac and renal function. Exercise training improved cardiac function, decreased plasma B-type natriuretic peptide levels, decreased urinary albumin excretion and increased creatinine clearance in CHF rats. Nitric oxide synthase activity, eNOS expression and neuronal (n) NOS expression were significantly decreased in the left ventricle and kidney of CHF rats. Exercise training significantly increased NOS activity and eNOS and nNOS expression. Upregulation of NOS in the kidney and left ventricle may contribute, in part, to the renal and cardiac protective effects of exercise training in cardiorenal syndrome in CHF rats.

Expression and cellular localization of inducible nitric oxide synthase in lipopolysaccharide-treated rat kidneys

Although inducible nitric oxide synthase (iNOS) is known to play significant roles in the kidney, its renal localization has long been controversial. To resolve this issue, the authors identified iNOS-positive cell types in rat kidneys using double immunohistochemistry and confirmed iNOS positivity using enzyme histochemistry with NADPH-diaphorase (NADPH-d) and in situ RT-PCR. Adult male Sprague-Dawley rats were injected intraperitoneally with lipopolysaccharide (LPS) or saline as a control and sacrificed at various time intervals after injection. Quantitative real-time reverse transcriptase polymerase chain reaction showed that iNOS was not expressed in control kidneys but was induced in LPS-treated kidneys. iNOS immunostaining was strongest 6 to 18 hr after injection and decreased gradually to control levels by day 7. Double immunohistochemistry and NADPH-d revealed that iNOS expression was induced in the interstitial cells, glomerular parietal epithelial cells, the proximal part of the short-looped descending thin limb, the upper and middle papillary parts of the long-looped descending thin limb, some inner medullary collecting duct cells, and almost all calyceal and papillary epithelial cells. The present study determines the precise localization of iNOS in LPS-treated rat kidneys and provides an important morphological basis for examining the roles of iNOS in sepsis-induced acute kidney injury.

Muscarinic receptors and their mRNAs in type 2 Goto-Kakizaki diabetic rat prostate

BACKGROUND

As increasing evidence is pointing towards the relationship between diabetes and benign prostatic hyperplasia/lower urinary tract symptoms, we investigated the pharmacological properties and gene expressions of the muscarinic receptors in type 2 diabetes rat prostate.

METHODS

Twelve- and 70-week-old male Goto-Kakizaki (GK) rats and age-matched male Wistar rats were used in this study. The densities of muscarinic receptors (B(max) values) were determined by saturation studies with [(3)H]NMS ([N-methyl-(3)H] scopolamine methyl chloride) in the prostatic membrane particulates. The participation levels of M(1), M(2), and M(3) receptor protein and mRNA levels in the prostate were investigated by immunoblot analysis and real-time polymerase chain reaction (PCR), respectively.

RESULTS

The B(max) values in 12-week-old Wistar and GK, and in 70-week-old Wistar and GK rat prostates were 36.0 +/- 2.8, 49.4 +/- 11.4, 22.0 +/- 2.2, and 47.0 +/- 4.1 fmol/mg protein, respectively. However, there were no significant differences in the affinity constants between any groups. Immunoblot analysis showed the existence of significant amounts of M(1), M(2), and M(3) receptor subtypes in each rat prostate. According to real-time PCR studies the rank order of expression levels of muscarinic receptors mRNA subtypes in the prostate were M(3) > M(2) > M(1). In each receptor subtype in each group, diabetes induced up-regulation of mRNAs while the advanced age of the rats was related with down-regulation of mRNAs.

CONCLUSIONS

Our data indicated that type 2 diabetes induced up-regulation and age-related down-regulation of the expressions of muscarinic receptors and their mRNAs in the rat prostate.

Inhibitory effects of aminoguanidine on thyroid follicular carcinoma development in inflamed capsular regions of rats treated with sulfadimethoxine after N-bis(2-hydroxypropyl)nitrosamine-initiation

We have reported that thyroid capsular thickening with inflammation induced by an antithyroidal agent, sulfadimethoxine (SDM), might play a role in the development of invasive follicular carcinomas in rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). Inducible nitric oxide synthase (iNOS) expressed in the inflamed capsular regions further appeared to be implicated in the tumor progression. In the present study, the effects of an iNOS inhibitor, aminoguanidine (AG), on thyroid carcinogenesis were examined. F344 male rats were treated with SDM in drinking water (0.1%) with or without concomitant dietary administration of AG (0.2%) for 4 and 10 weeks after subcutaneous injection of DHPN at 2800 mg/kg bodyweight. At week 4, thyroid capsular thickening with inflammation was observed and iNOS-positive foci were found in the inflamed regions. In addition, single-strand DNA-positive inflammatory cells were scattered among neighboring follicular cells, indicating some cellular damage, at least partly in association with iNOS induction. Concurrent dietary administration of AG with SDM treatment slightly decreased the number of single-strand DNA-positive cells but did not alter the incidence and multiplicity of iNOS-positive foci in the inflamed capsular regions at week 4. At week 10, however, invasive follicular carcinomas predominantly arose in the thickened capsule in the DHPN-SDM-treated rats, and AG administration decreased (P < 0.05) their multiplicity. The carcinoma cells were partly positive for iNOS. These results thus suggested that iNOS induction in both inflammatory and tumor cells might play pivotal roles in tumor progression in this DHPN-SDM rat model.

Effects of a selection of histone deacetylase inhibitors on mast cell activation and airway and colonic smooth muscle contraction

Studies of histone deacetylase (HDAC) inhibitors, novel anticancer drugs, in models of autoimmune diseases, asthma, and inflammatory bowel disease suggest that HDAC inhibitors may also have useful anti-inflammatory effects. Accordingly, in vitro studies relevant to asthma and inflammatory bowel disease were conducted using a selection of HDAC inhibitors: suberoylanilide hydroxamic acid (SAHA, Vorinostat), and a related branched hydroxamic acid, diamide (1), MGCD0103 and two short chain fatty acid derivatives: sodium butyrate (of use in inflammatory bowel disease) and sodium valproate. The ability of those HDAC inhibitors to modulate antigen- or agonist-induced contraction of isolated guinea pig tracheal rings and colon, agonist-induced contraction of rat colon, and histamine release from rat peritoneal mast cells was examined. Pre-incubation (up to 6 h) with 10-40 microM of SAHA, diamide (1), or MGCD0103 caused significant inhibition of the antigen-induced contraction of sensitised guinea pig tracheal rings as well as inhibition of the contraction induced by histamine, 5-hydroxytryptamine and carbachol (G-protein coupled receptor agonists), while sodium butyrate (1 mM) and sodium valproate (100 microM) were weak inhibitors. Contraction of tracheal rings by sodium fluoride (NaF, a non-selective G-protein activator), KCl and a peroxyl radical generator was blocked by MGCD0103. Additionally, MGCD0103 significantly inhibited antigen-induced histamine release from IgE antibody-sensitised rat peritoneal mast cells, and NaF-induced histamine release, as well as inhibiting NaF-induced colon contraction. Those various effects appear to involve modulation of cell signaling, probably involving G-protein coupled pathways, and further support the development of HDAC inhibitors as anti-inflammatory agents.

Mitochondrial function and nitric oxide metabolism are modified by enalapril treatment in rat kidney

The renal and cardiac benefits of renin-angiotensin system (RAS) inhibition in hypertension exceed those attributable to blood pressure reduction, and seem to involve mitochondrial function changes. To investigate whether mitochondrial changes associated with RAS inhibition are related to changes in nitric oxide (NO) metabolism, four groups of male Wistar rats were treated during 2 wk with a RAS inhibitor, enalapril (10 mg x kg(-1) x day(-1); Enal), or a NO synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME) (1 mg x kg(-1) x day(-1)), or both (Enal+L-NAME), or were untreated (control). Blood pressure and body weight were lower in Enal than in control. Electron transfer through complexes I to III and cytochrome oxidase activity were significantly lower, and uncoupling protein-2 content was significantly higher in kidney mitochondria isolated from Enal than in those from control. All of these changes were prevented by L-NAME cotreatment and were accompanied by a higher production/bioavailability of kidney NO. L-NAME abolished mitochondrial NOS activity but failed to inhibit extra-mitochondrial kidney NOS, underscoring the relevance of mitochondrial NO in those effects of enalapril that were suppressed by L-NAME cotreatment. In Enal, kidney mitochondria H(2)O(2) production rate and MnSOD activity were significantly lower than in control, and these effects were not prevented by L-NAME cotreatment. These findings may clarify the role of NO in the interactions between RAS and mitochondrial metabolism and can help to unravel the mechanisms involved in renal protection by RAS inhibitors.

Effect of spironolactone and captopril on nitric oxide and S-nitrosothiol formation in kidney of L-NAME-treated rats

Although angiotensin-converting enzyme (ACE) inhibitors are well-established drugs in the treatment of hypertension, they are not supposed to be sufficient in the inhibition of aldosterone formation. The present study analyzes the effect of aldosterone receptor antagonist, spironolactone and ACE inhibitor, captopril on nitric oxide (NO) and S-nitrosothiol formation in the kidney of N(G)-nitro-L-arginine methyl ester (L-NAME)-treated rats. Male Wistar rats were divided into six groups: (1) controls, (2) L-NAME (40 mg/kg/day), (3) spironolactone (200 mg/kg/day), (4) captopril (100 mg/kg/day), (5) L-NAME+spironolactone, and (6) L-NAME+captopril. After 4 weeks, NO synthase (NOS) activity, protein expression of endothelial NOS, inducible NOS and concentration of thiol and S-nitrosothiol groups were determined in the kidney. Besides the increase in systolic blood pressure (by 32%) and the decrease in NOS activity (by 37%), L-NAME treatment lowered the concentration of thiols (by 32%) and S-nitrosothiols (by 36%) in the renal tissue. Simultaneous treatment with spironolactone preserved NOS activity and S-nitrosothiols on the control level, whereas captopril did not affect these parameters modified by L-NAME treatment. Moreover, spironolactone increased expression of endothelial NOS protein without affecting inducible NOS protein expression. In conclusion, both captopril and spironolactone prevented L-NAME-induced hypertension and the decline of the antioxidant potential of the kidney tissue. However, only spironolactone improved NOS activity which led to the S-nitrosothiols formation. Both NO itself and S-nitrosothiols may contribute to the preventive effect of spironolactone against development of L-NAME-induced hypertension.

Activity and expression of semicarbazide-sensitive benzylamine oxidase in a rodent model of diabetes: interactive effects with methylamine and alpha-aminoguanidine

Previous data indicate that methylamine injection in fasted healthy mice produced a hypophagic effect dependent of neuronal K(v)1.6 channels expression and increased by alpha-aminoguanidine, an inhibitor of semicarbazide-sensitive benzylamine oxidase enzymes mainly involved in amine degradation. In the present work we have investigated: 1) the level of expression and activity of the semicarbazide-sensitive benzylamine oxidase; 2) the effect of methylamine alone and in the presence of alpha-aminoguanidine on food intake of genetic obese and type II diabetes mice (the db/db mice). Db/db mice showed higher levels of semicarbazide-sensitive benzylamine oxidase activities in adipose tissue and in plasma than their lean counterpart (db/db(+) mice). Methylamine (30-75 microg, i.c.v.) showed similar hypophagic effects in obese and lean mice consistently with the levels of neuronal K(v)1.6 found in both animal strains. Alpha-aminoguandine (50 mg/kg, i.p.) increased methylamine (i.c.v.) hypophagia in both obese and lean mice and only in obese mice when methylamine was given i.p. These results suggest a crucial role of semicarbazide-sensitive benzylamine oxidase activity in controlling methylamine hypophagia in hyperphagic diabetic mice.

Effects of chronic inhibition of inducible nitric oxide synthase in hyperthyroid rats

We hypothesized that nitric oxide generated by inducible nitric oxide synthase (iNOS) may contribute to the homeostatic role of this agent in hyperthyroidism and may, therefore, participate in long-term control of blood pressure (BP). The effects of chronic iNOS inhibition by oral aminoguanidine (AG) administration on BP and morphological and renal variables in hyperthyroid rats were analyzed. The following four groups (n = 8 each) of male Wistar rats were used: control group and groups treated with AG (50 mg.kg(-1).day(-1), via drinking water), thyroxine (T4, 50 microg.rat(-1).day(-1)), or AG + T4. All treatments were maintained for 3 wk. Tail systolic BP and heart rate (HR) were recorded weekly. Finally, we measured BP (mmHg) and HR in conscious rats and morphological, plasma, and renal variables. T(4) administration produced a small BP (125 +/- 2, P < 0.05) increase vs. control (115 +/- 2) rats. AG administration to normal rats did not modify BP (109 +/- 3) or any other hemodynamic variable. However, coadministration of T4 and AG produced a marked increase in BP (140 +/- 3, P < 0.01 vs. T4). Pulse pressure and HR were increased in both T4- and T4 + AG -treated groups without differences between them. Plasma NOx (micromol/l) were increased in the T4 group (10.02 +/- 0.15, P < 0.05 vs. controls 6.1 +/- 0.10), and AG reduced this variable in T4-treated rats (6.81 +/- 0.14, P < 0.05 vs. T4) but not in normal rats (5.78 +/- 0.20). Renal and ventricular hypertrophy and proteinuria of hyperthyroid rats were unaffected by AG treatment. In conclusion, the results of the present paper indicate that iNOS activity may counterbalance the prohypertensive effects of T4.

Nitric oxide synthase expression in AT2 receptor-deficient mice after DOCA-salt

BACKGROUND

Angiotensin II type 2 receptor-deficient mice (AT(2)-/y) provide an opportunity to study the relationship between the angiotensin II type 1 receptor (AT(1)) and nitric oxide synthase (NOS) isoforms without concomitant AT(2) receptor-related effects. To test this relationship, the expression of renal NOS isoforms (neural, inducible, and endothelial) in AT(2)-/y and AT(2)+/y mice was examined. The mice were challenged with deoxycorticosterone acetate (DOCA)-salt to stimulate NO generation.

METHODS

Gene expression analyses by real-time polymerase chain reaction (PCR) (TaqMan) were performed in kidneys to characterize neuronal nitric oxide synthase (nNOS), epithelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and the AT(1) receptor. Pressure-natriuresis experiments were done to determine the physiologic background.

RESULTS

AT(2)-/y mice showed nNOS and iNOS up-regulation. DOCA-salt increased iNOS expression more in AT(2)-/y mice than in AT(2)+/y mice. Immunohistochemistry localized the iNOS expression with DOCA-salt mainly in the glomeruli. eNOS was not different between the groups, and was not affected by DOCA-salt. DOCA-salt increased mean arterial pressure more in AT(2)-/y mice than in AT(2)+/y mice. Concomitantly, the pressure-natriuresis relationship was shifted to the right in AT(2)-/y and AT(2)+/y mice after DOCA-salt. DOCA-salt decreased renal blood flow (RBF) and glomerular filtration rate (GFR) in both groups. iNOS blockade did not lower blood pressure.

CONCLUSION

We conclude that AT(2) receptor deletion and concomitant up-regulation of the AT(1) receptor is associated with up-regulation of nNOS and iNOS. Under DOCA-salt, renal iNOS expression was further increased. Because iNOS inhibition did not change blood pressure, iNOS may not be involved in the hemodynamics, but may contribute to organ damage.

Protection of wistar furth rats from chronic renal disease is associated with maintained renal nitric oxide synthase

Wistar Furth (WF) rats do not develop renal injury after severe reduction of renal mass. Because clinical and animal studies suggested that nitric oxide (NO) deficiency occurs and may contribute to chronic renal disease (CRD), the status of the NO system in WF versus Sprague Dawley (SD) rats was examined with the 5/6 renal ablation/infarction (A/I) model of CRD. Eleven weeks after A/I, SD rats developed proteinuria, severe kidney damage, decreased renal function, and marked decreases in total and renal NO synthase (NOS), specifically neuronal NOS. In contrast, WF rats exhibited elevated baseline and maintained post-A/I total NO production, with no decrease in renal cortex NOS activity despite a decrease in remnant neuronal NOS abundance. When low-dose chronic Nomega-nitro-L-arginine methyl ester treatment was added for WF A/I-treated rats, rapid progression of CRD was observed. In conclusion, elevated NO production in WF rats was associated with protection from the progression of CRD after renal mass reduction. The protection might be attributable to greater total and renal NO-generating capacity and increased nephron number, compared with SD rats. NOS inhibition rendered WF rats susceptible to progression, suggesting a possible critical threshold for NO production, below which renal injury occurs.

Protection against puromycin aminonucleoside-induced chronic renal disease in the Wistar-Furth rat

The Wistar-Furth (WF) rat is protected against chronic renal disease (CRD) following 5/6th ablation/infarction vs. the Sprague-Dawley (SD) rat, and protection was associated with preserved renal nitric oxide (NO) production. This study examined CRD induced with repeated administration of puromycin aminonucleoside (PAN). SD PAN developed nephrotic range proteinuria (>1 g/24 h), and at 15 wk severe renal injury developed and the glomerular filtration rate (GFR) was reduced to approximately 10% of sham. Total NO production, renal NO synthase (NOS) activity, and renal neuronal (n) and medullary endothelial (e)NOS abundance were reduced in the SD PAN. WF PAN exhibited less severe initial proteinuria (>400 mg/24 h), which abated within weeks, whereas GFR was normal and injury was minimal at 15 wk. Total NO production and renal NOS activity and abundance were significantly elevated compared with SD PAN. NOS mRNA (nNOS, eNOS, and inducible NOS) was not altered in WF, whereas SD showed significant increases in NOS gene expression with PAN. In conclusion, WF showed resistance to a second model of CRD with maintained renal NOS activity compared with SD.

Dietary L-Arginine Supplementation Improves the Glomerular Filtration Rate and Renal Blood Flow After 24 Hours of Unilateral Ureteral Obstruction in Rats

PURPOSE

Unilateral ureteral obstruction (UUO) results in a significant change in renal blood flow (RBF) and glomerular filtration rate (GFR) by 24 hours. The intake of L-arginine, a substrate of nitric oxide (NO) synthase (NOS), can augment NO production. NO can maintain renal function through its vasodilatory action. Therefore, we examined the effect of dietary arginine supplementation on renal function in UUO.

MATERIALS AND METHODS

GFR and RBF were measured by inulin and para-aminohippurate clearance, respectively, in control rats and in rats 24 hours after UUO. Rats were given arginine with or without the concomitant administration of N-nitro-L-arginine methyl ester. Urinary nitrate/nitrite (NO2/NO3) was measured by the Griess reaction and urinary cyclic guanosine monophosphate was determined by enzyme-linked immunosorbent assay. The expression of renal inducible NOS was determined by immunohistochemistry.

RESULTS

Urinary NO2/NO3 was significantly increased after 2 weeks of arginine, confirming increased NO production. In control rats GFR and RBF were not significantly different in untreated vs arginine treated groups. In contrast, arginine treatment significantly increased GFR in the obstructed kidney (0.06 +/- 0.01 to 0.14 +/- 0.02 ml per minute per 100 gm) and the contralateral kidney compared with control UUO. RBF was also significantly increased by arginine. The increases in renal function with arginine were blunted by a NOS inhibitor in obstructed and contralateral kidneys. Inducible NOS expression was increased in obstructed and contralateral kidneys.

CONCLUSIONS

This study demonstrates that L-arginine supplementation can improve renal function in acute UUO. This finding suggests that NO system may be a future site of pharmacological intervention for UUO.