Effect of cross-fostering on blood pressure and renal function in the New Zealand genetically hypertensive rat

1. The severity of hypertension displayed by adult spontaneously hypertensive rats (SHR) and Dahl (SS/Jr) rats can be reduced by 20-30 mmHg if the hypertensive pup is cross-fostered to a normotensive mother within the first 2 weeks of birth. In the SHR, at least, this blood pressure-lowering effect arises through programming of the neonatal kidney to excrete sodium more effectively. Thus, cross-fostering may only be effective in lowering pressure in salt-sensitive hypertensive strains. Accordingly, the aim of the present study was to determine whether cross-fostering is effective in lowering adult blood pressure in the salt-resistant New Zealand genetically hypertensive (GH) rat. 2. Genetically hypertensive and control normotensive (N) rat pups were reared by either their natural mothers or a foster mother of the opposite strain (NX and GHX). Blood pressure was tracked from the age of 6-18 weeks, at which time renal function was assessed using standard clearance techniques in anaesthetized rats. Renal function was also assessed in a separate group of young rats at 5-6 weeks of age. 3. Cross-fostered GHX rats had lower blood pressure than GH rats, but this difference was only apparent until 9 weeks. The NX rats had higher blood pressures than N rats, but again pressure converged at 10 weeks. Basal renal function did not differ between GH and GHX rats or between N and NX rats at either age. However, young GH rats had lower renal blood flow, glomerular filtration rate, urine output and sodium excretion than N rats. 4. These data show that cross-fostering is effective in lowering blood pressure in GH rats, albeit transiently. The kidneys do not appear to play a role, because renal function did not differ under the current experimental conditions between GH and GHX rats. However, the kidney may play a greater role in the onset of hypertension in the GH rat than previously thought.     

Failure of an angiotensin II antagonist to influence isoprenaline-induced antidiuresis in rats

Summary The purpose of this study was to elucidate the role of angiotensin II in isoprenaline-induced antidiuresis by use of the competitive angiotensin II antagonist saralasin. Isoprenaline is known to enhance the formation of angiotensin II. Since angiotensin II has been shown to increase proximal tubular salt and volume reabsorption and to decrease renal fluid and salt excretion the renal effects of isoprenaline might, at least partly, be mediated by angiotensin II.Isoprenaline, infused at 0.1 g/kg·min i. v. into anaesthetized rats, led to a marked decrease of urine flow, sodium and potassium excretion and to an increase in urinary osmolality, confirming previous data. Effective renal plasma flow increased significantly. Immediately after onset of the isoprenaline infusion a transient small fall in GFR was observed. On continuation of the infusion, GFR recovered, but marked antidiuresis persisted. Changes in renal hemodynamics, therefore, can be excluded as being responsible of the antidiuretic effect. Saralasin, infused at 6 g/kg· min i.v., did not affect isoprenaline-induced antidiuresis, antinatriuresis, antikaliuresis, and the increase in urinary osmolality, but prevented the rise in renal plasma flow observed during isoprenaline infusion, probably as a consequence of a weak angiotensin II-like effect of saralasin on renal vessels.It is concluded that angiotensin II does not play a role in isoprenaline-induced antidiuresis. The results are compatible with the view that -adrenoceptor stimulation may directly affect the tubular handling of water and salt.     

不同程度慢性乙型肝炎患者肾功能评估及危险因素分析

目的 对不同程度慢性乙型肝炎（CHB）患者肾功能进行评估,分析正规抗病毒治疗对CHB患者肾功能的影响,分析CHB患者肾功能损伤的危险因素。方法 收集2015年1月至2016年4月于安徽医科大学第一附属医院379例CHB患者,按照CHB临床分度将患者分为轻度组（191例）、中度组（123例）、重度组（65例）3组,采用简化MDRD方程计算CHB患者肾小球滤过率（eGFR）。分析不同程度CHB患者肾功能有无差异,正规抗病毒治疗对不同程度CHB患者肾功能的影响及年龄、性别、HBeAg、HBV DNA等对CHB患者肾功能的影响。结果 轻度组患者eGFR水平为（73.10±14.42）mL/（min·1.73m²）,中度组患者eGFR水平为（65.17±11.42）mL/（min·1.73m²）,重度组患者eGFR水平为（59.72±18.59）mL/（min·1.73m²）,3组间eGFR水平差异具有统计学意义（F=25.200,P=0.000）;CHB患者肝炎病情程度和年龄是引起CHB患者出现肾功能损伤的危险因素（P<0.05）。结论 CHB患者eGFR水平与病情程度相关,轻度和中度正规抗病毒治疗的CHB患者eGFR水平较未正规抗病毒治疗者eGFR水平高,肝炎病情程度与年龄是引起CHB患者出现肾功能损伤的危险因素。     

Effects of ozolinone,a diuretic active metabolite of etozoline,on renal function

Summary The renal action of 3-methyl-4-oxo-5-piperidino-thiazolidine-2-ylidine (ozolinone), a metabolite of the diuretic etozoline (Elkapin), was studied in anaesthetized dogs after i.v. injection and compared with the renal effects of furosemide. The diuretic action of ozolinone was rapid in onset and of short duration. Thesmallest effective i.v. dose was 1 mg\kg^–1. Maximal diuretic capacity was reached at 50 mg\kg^–1 i.v. Fractional tubular sodium reabsorption was depressed to 67% at maximal effective doses.Ozolinone had similar renal actions to those of furosemide. Like furosemide, ozolinone increased renal blood flow, slightly decreased glomerular filtration rate, depressed tubular chloride reabsorption more than sodium reabsorption, increased potassium excretion, lowered the pH of urine, decreased urinary osmolarity towards isotonicity and depressed tubular PAH secretion. As regards the effective doses and the maximal changes of tubular sodium excretion, ozolinone was somewhat less potent than furosemide.     

RENAL RESPONSES TO ANGIOTENSIN II IN CONSCIOUS DOGS: EFFECTS OF ASPIRIN AND INDOMETHACIN

1. Angiotensin II was infused into the renal artery of unanaesthetized dogs at 0.4 and 2.0 ng/kg per min for 40 min each. 2. Indomethacin (3 mg/kg, and 1 mg/kg per h infusion i.v.) accentuated the angiotensin II-induced falls in glomerular filtration rate, renal blood flow and urine flow rate. Indomethacin did not alter the effects of angiotensin II on Na+ or K+ excretions. 3. Aspirin (35 mg/kg p.o. 2.5 h and 0.5 h prior to experiment) did not significantly change the renal effects of angiotensin II. 4. Both aspirin and indomethacin accentuated renal vasoconstriction during briefer (5 min) angiotensin II infusion. 5. Thus indomethacin and aspirin had markedly different effects on the actions of angiotensin II in the kidney. This suggests that at least one of these drugs has actions which affect angiotensin II-mediated vasoconstriction other than via cyclooxygenase inhibition.     

Effect of the adenosine antagonist 8-phenyltheophylline on glycerol-induced acute renal failure in the rat.

8-Phenyltheophylline (8-PT)(10 mg kg-1) or its vehicle(1 ml kg-1) were administered intravenously or intraperitoneally twice daily over 48 h to rats with acute renal failure (ARF) induced by intramuscular (i.m.) injection of glycerol. Rats treated with 8-PT i.v. had significantly lower plasma urea and creatinine levels at 24 and 48 h compared to untreated animals. The vehicle also reduced plasma urea and creatinine when compared to untreated controls. However, plasma urea levels in 8-PT-treated rats were significantly lower than in vehicle-treated animals at 24 and 48 h after both i.v. and i.p. administration. Plasma creatinine concentrations also tended to be lower in the 8-PT-treated group. [3H]-inulin clearance at 48 h after i.m. glycerol was significantly greater in rats dosed i.p. with 8-PT compared to either untreated or vehicle treated rats. Examination of kidneys taken from rats 48 h after i.m. glycerol showed that 8-PT treatment significantly reduced renal damage and kidney weight compared to the untreated or vehicle-treated groups. In a 7 day study all the rats which received 8-PT i.p. survived whilst in the vehicle and untreated groups the mortality rates were 12 and 21% respectively. In a separate series of experiments 8-PT (10 mg kg-1, i.v. or i.p.) was found to antagonize adenosine-induced bradycardia in conscious rats for up to 5 h. There is no clear explanation for the partial protection afforded by the vehicle but it may be related to either its alkalinity or an osmotic effect produced by the polyethylene glycol component.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of glucagon on the renal hemodynamics of dogs

An intrarenal infusion of glucagon resulted in an increase of glomerular filtration rate (GFR) with the same order of magnitude of renal blood flow (RBF) but did not affect the intrarenal distribution of blood flow. A superimposition of acetylcholine and glucagon decreased GFR even though RBF increased significantly. These findings indicate that the effect of glucagon on GFR depended on the selective dilation of afferent arterioles without any change in permeability of glomerular capillaries and redistribution of filtration.     

Distal nephron function of the rat during acute aflatoxicosis

The effect of an acute intoxication with aflatoxin B1 (AFB1) on some parameters of distal nephron function was examined in rats 48 h after a single i.p. dose of 100 micrograms/kg body wt. The parameters tested were the capacity for the excretion of fixed acids and ammonium salts during metabolic acidosis and the concentration and dilution of urine applying conventional clearance techniques. The treated rats showed a glomerular filtration rate (GFR) approx. 50% lower than the controls, but they were able to reduce the urinary pH as were nonintoxicated animals. The ammonium excretion rate per ml of GFR was unimpaired in the treated rats, but the rate of excretion of fixed acids per ml of GFR was increased. The maximal urinary osmolality was significantly diminished in the intoxicated rats as was water reabsorption, when compared with data obtained in the controls. No differences between groups were seen in the free water formation although urinary excretion of electrolytes was significantly increased. The studies support the nephrotoxicity of AFB1 in the rat probably by interfering with transport function in the collecting tubule cells together with a diffuse impairment of proximal tubule function, as observed previously.     

血清胱抑素C的检测对早期肾功能损害价值的探讨

目的 探讨血清胱抑素C（Cys-C）的检测在诊断早期肾功能损害中的应用价值.方法 将253例肾损害疾病患者根据肌酐清除率（Ccr）测量值大小分为肾功能正常组（A组）、肾功能轻度损害组（B组）、肾功能中度损害组（C组）、重度损害及尿毒症组（D组）4组,选取60名作为健康对照组,用颗粒增强散射免疫法检测血清Cys-C的浓度,同时用酶法检测血肌酐（Scr）、血尿素氮（BUN）、肌酐清除率（Ccr）,并对各组血清Cys-C、Scr和BUN进行分析比较.结果 肾病患者中肾功能正常组（A组）和肾功能轻度损害组（B组）仅Cys-C与健康对照组差异有高度统计学意义（P〈0.01）,而在肾功能中度损害组（C组）、重度损害及尿毒症组（D组）的Cys-C、Scr和BUN均与健康对照组差异有统计学意义（P〈0.01或P〈0.05）.结论 血清Cys-C是肾功能早期损害的灵敏诊断指标,可早期判断肾小球滤过功能损害.     

Natriuresis, kaliuresis and diuresis in the rat following microinjections of carbachol into the septal area.

The effects of intraseptal injection of carbachol on natriuresis, kaliuresis and diuresis has been studied in conscious, unrestrained water-loaded male rats. Urinary sodium and potassium excretion increased following injections into the septal area. The intensity of the natriuresis and kaliuresis was dose-related. An antidiuretic effect was also observed. The Na+/K/ ratio increased with increasing doses of carbachol, indicating that the rise in urinary sodium exceeded that of potassium. Systematic mapping of the septal area yielded about the same results for all sites, excepting a zone located in the anterior-dorsal part of the medial nucleus which appeared more sensitive. The natriuretic effect of intraseptal carbachol in adrenalectomized rats demonstrated the secondary role played by the adrenals. Contrariwise the decrease of the natriuretic effect observed either in hypophysectomized rats or in rats bearing a median eminence lesion receiving intraseptal carbachol showed the important participation of these structures in urinary Na+ excretion. Adrenalectomy or median eminence lesions did not modify the kaliuretic response while hypophysectomy produced a transitory diminution. This fact favours the hypothesis of different mechanisms involved in Na+ and K+ excretion following intraseptal carbachol. These results leave open the question as to mechanism of action but suggest a possible role of the pituitary in mediating the responses. Also, the possibility of a role played by hemodynamic shifts is suggested.     

肾小球滤过率测算公式的计算机智能系统建立及临床应用研究

目的 建立肾小球滤过率(GFR)测算公式的计算机智能系统(CIS),并进行临床应用研究,评估其临床应用价值.方法 用VB编程,创建GFR测算公式的CIS,安装于专用计算机内使用.采用99mTc-DTPA清除率准确测定140例慢性肾衰竭(CRF)住院患者(肾功能不全组)与135例肾功能尚正常的其它肾病患者(肾功能正常组)的GFR(Tc-GFR),同时测血清胱抑素C(SCys-C)及肌酐(SCr)等指标,分别用Cockcroft/Gault公式计算内生肌酐清除率(CG-CCr)、CKDEPI等公式测算出GFR(CKDEPI · SCr-eGFR)等,对所得数据进行统计学分析.结果 CG-CCr、Filler G,et al· SCysC-eGFR、Rule·SCysC-eGFR与Tc-GFR差异有统计学意义(P＜0.05),肾功能不全者中,国内健康人·SCr&SCysC-eGFR与Tc-GFR也有统计学差异,其它公式eGFR与Tc-GFR均无统计学差异(均P＞0.05).结论 CIS较手工计算GFR简便、快速、数值精准,临床工作中应选择准确可靠的公式.     

Mechanisms of bee venom-induced acute renal failure.

The spread of Africanized bees in the American continent has increased the number of severe envenomation after swarm attacks. Acute renal failure (ARF) is one of the major hazards in surviving patients. To assess the mechanisms of bee venom-induced ARF, rats were evaluated before, up to 70 min and 24h after 0.5mg/kg of venom injection. Control rats received saline. Bee venom caused an early and significant reduction in glomerular filtration rate (GFR, inulin clearance, 0.84+/-0.05 to 0.40+/-0.08 ml/min/100g, p<0.0001) and renal blood flow (RBF, laser Doppler flowmetry), which was more severe in the cortical (-72%) than in the medullary area (-48%), without systemic blood pressure decrease. Creatine phosphokinase, lactic dehydrogenase (LDH) and serum glutamic oxaloacetic transaminase increased significantly, pointing to rhabdomyolysis, whereas serum glutamic pyruvic transaminase and hematocrit remained stable. Twenty-four hours after venom, RBF recovered but GFR remained significantly impaired. Renal histology showed acute tubular injury and a massive tubular deposition of myoglobin. Venom was added to isolated rat proximal tubules (PT) suspension subjected to normoxia and hypoxia/reoxygenation (H/R) for direct nephrotoxicity evaluation. After 60 min of incubation, 0.1, 2 and 10 microg of venom induced significant increases in LDH release: 47%, 64% and 86%, respectively, vs. 21% in control PT while 2 microg of venom enhanced H/R injury (85% vs. 55%, p<0.01). These results indicate that vasoconstriction, direct nephrotoxicity and rhabdomyolysis are important mechanisms in the installation of bee venom-induced ARF that may occur even without hemolysis or hypotension.     

Effects of statin treatment in men and women with stable coronary heart disease: a subgroup analysis of the GREACE Study

ABSTRACT

Background: Reducing low-density lipoprotein cholesterol (LDL-C) levels to National Cholesterol Expert Panel (NCEP) goal is recommended. However, sex-specific effects may influence benefit.

Methods and results: In this post hoc analysis of the GREek Atorvastatin and Coronary heart disease (CHD) Evaluation [GREACE] study we investigated the extent in vascular event reduction by statin treatment according to sex. From a total of 1600 patients with stable CHD, 624/176 and 632/168 were men/women on atorvastatin or on usual care, respectively. During 3-year follow-up, comparison of atorvastatin treatment with usual care demonstrated a relative risk reduction (RRR) of the primary end point (all vascular events) of 54?%?in women (hazard ratio [HR] 0.46, 95?%?confidence interval [CI] 0.24–0.87, p?=?0.003) and of 50?%?in men (HR 0.50, 95?%?CI 0.32–0.70, p?<?0.001). The fall in LDL-C levels played the key role in end point reduction in both sexes. However, in men there was an additional benefit related to the atorvastatin-induced increase in high density lipoprotein cholesterol (HDL-C) and estimated glomerular filtration rate (eGFR), while in women end points were related to a substantial triglycerides (TG) reduction.

Conclusions: Treatment with atorvastatin to the NCEP LDL-C goal compared with “usual care” significantly reduced CHD morbidity and mortality in both men and women. Both men and women benefited from statin treatment possibly with different mechanisms making a contribution over and above LDL-C reduction.     

Effects of chitosan oligosaccharide (COS) on the glycerol-induced acute renal failure in vitro and in vivo.

The purpose of this study was to investigate the effects of chitosanoligosaccharide (COS) on the change of inflammatory response, renal function factor, and renal oxidative stress in glycerol-induced ARF in vitro and in vivo. The molecular weight of COS was approximately below 10 kDa with 90% degree of deacetylation. Renal proximal tubular cells were treated with only COS (0, 0.01, 0.025, 0.05, 0.075 and 0.1%) or COS in the presence of glycerol (4mM). And rats were administered with glycerol (50%, 8 ml/kg) by intramuscular injection for the induction of ARF. For identification the protection effect of COS in the glycerol-induced ARF, rats were administered by COS (0.05 and 0.1%) using P.O. injection. The enzymatic activity of the released RDPase was assayed by the fluorometric method. The level of TNF-alpha in kidney or the culture medium was quantified using ELISA kit (R&D Systems, Minneapolis, USA) and, nitrite concentration was determined by the Griess reaction. We showed that COS stimulated the production of TNF-alpha, NO and the released RDPase. Glycerol increased the concentration of RDPase in kidney and decreased the released RDPase in proximal tubular cells. And, glycerol increased the production of NO, TNF-alpha, creatinine, and MDA, and decreased SOD. However, COS recovered the glycerol-induced inflammatory response, renal function factor, and antioxidant effect in kidney. COS had the antioxidant activity and the anti-inflammatory effect. And maybe that characteristics could help recover the glycerol-induced ARF.     

Comparison of the effects of propranolol and labetalol on renal haemodynamics at rest and during exercise in essential hypertension

Summary The effect of exercise on renal haemodynamics was examined in young patients with mild essential hypertension. Four groups of subjects were studied: 13 normotensive, healthy control subjects, and 15 untreated, 11 propranolol-treated, and 6 labetalol-treated patients. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were measured during four consecutive periods, a pre-exercise control period, two exercise periods with loads of 450 kpm/min and 600 kpm/min, respectively, and a post-exercise control period. In the untreated patients RPF and GFR were lower during exercise than in the normotensive control subjects, whereas no significant differences were found at rest. In the propranolol-treated patients the reduction in RPF and GFR during exercise was more pronounced than in the untreated hypertensives. In the labetalol-treated patients however, RPF and GFR were reduced only to the same degree as in the untreated hypertensives. The reduced renal blood flow in propranolol-treated patients may be attributed to a compensatory increase in sympathetic activity caused by an impaired cardiac response to exercise. The lack of reduction in renal blood flow during labetalol therapy could partly be related to alpha-adrenergic blockade in the renal vascular bed induced by labetalol, and partly to the smaller reduction in cardiac output during labetalol than during propranolol therapy.     

Amplification by atrial natriuretic peptide of the haemodynamic and renal responses to an acute volumic stress in the rat

1. The purpose of the present study was to test the effects of synthetic atrial natriuretic peptide (ANP) on renal haemodynamics and excretory capacities of salt and water in the rat during an 'acute volumic stress', which was induced by brisk disturbances of the circulatory volume. 2. To this end, 29 anaesthetized male Wistar rats were rapidly injected with 1 mL of 0.85% NaCl, repeated twice at 60 s intervals. The injectates contained no ANP (n = 5) or 1 x 0.25 (n = 6), 3 x 0.25 (n = 6), 1 x 2.5 (n = 6) or 3 x 2.5 micrograms (n = 6) ANP, added to the first injectate only (1 x) or to each injectate (3 x). Renal blood flow (RBF) was continuously measured with an electromagnetic flow transducer. 3. Renal blood flow increased transiently (approximately 30 s) by approximately 13% (P < 0.05) during each injection of saline without ANP. Addition of 0.25 or 2.5 micrograms ANP to the first injectate enhanced RBF by 21 and 35%, respectively (both P < 0.05), but did not modify the time sequence. Furthermore, addition of 0.25 microgram ANP to the second and third injectate produced an almost similar change in RBF at the end of each injection (delta RBF = 20 and 17%, respectively). In contrast, the addition of 2.5 micrograms ANP to the second and third injectate did not produce the same changes in RBF observed at the end of the first injection. The amplitude of the change in RBF was then similar to the increase in RBF induced by 1 mL saline without ANP. Mean arterial pressure (MAP) did not change significantly during repeated injections of saline alone or with addition of 0.25 microgram ANP to the first injectate. However, MAP decreased significantly (by 5, 9 and 9 mmHg) after the injection of 3 x 0.25, 1 x 2.5 or 3 x 2.5 micrograms ANP, respectively. 4. Sodium excretion was rapidly increased from 2.600 +/- 0.654 to 9.330 +/- 1.322 mumol/min after injection of 3 x 1 mL of 0.85% NaCl (P < 0.05). Thereafter, sodium excretion remained enhanced throughout the experiment, so that 70% of the sodium load injected was recovered at the end of the experiment. Atrial natriuretic peptide added to the injectates further elevated the maximal responses in diuresis and natriuresis induced by saline injections without ANP (P < 0.001). A maximal effect was observed after the addition of 2.5 micrograms ANP to the first saline solution. When the amount of sodium excreted was calculated by integrating the areas under the curve of the natriuretic responses, a relationship was established as a function of the amount of ANP added to the saline solutions. It was characterized by a threshold in the presence of 2.5 micrograms ANP added to the first injectate when the integration period was limited to 4 min 30 s and 14 min 30 s after starting the first injection of the varying test solutions. When the integration period was extended until the end of the experiment (2 h), the amount of sodium excreted in each group was further enhanced, especially after injection of 3 x 1 mL of 0.85% NaCl without ANP or with 1 x 0.25 and 3 x 0.25 microgram ANP. Differences in sodium excretion between groups were attenuated (P < 0.054, ANOVA). 5. In conclusion, our results demonstrate differential effects of synthetic ANP on renal vascular reactivity and excretory capacity. These effects were superimposed on changes induced by acute volumic stress. In particular, effects of saline injections on renal vascular compliance were amplified in the presence of ANP added in varying amounts to the injectates. This amplification was limited to 2.5 micrograms ANP.     

Effect of Prenalterol,a β-1-Adrenoceptor Agonist,on Renin Secretion Rate in the Anaesthetized Dog

Abstract: The effects of the β-1-adrenoceptor agonist, prenalterol, 20 μg/kg intravenously on renin secretion rate (RSR), renal haemodynamics and sodium excretion were examined in anaesthetized dogs with innervated or denervated kidneys. In dogs with innervated kidneys, prenalterol increased RSR from 1.1±0.2 to 7.9±0.1 unitsXmin.^?1Xg^?1 (P<0.01). Prenalterol did not affect mean arterial pressure, renal blood blow, glomerular filtration rate or sodium excretion. Heart rate was increased by 53±17 beats/min. (P<0.01). The increase in RSR produced by prenalterol was independent of intact renal innervation as RSR increased to the same extent in dogs with denervated kidneys. Pretreatment with the β-1-adrenoceptor antagonist, metoprolol 0.5 mg/kg intravenously, abolished the increase in RSR produced by prenalterol. These findings suggest that prenalterol directly activates renal β-1-adrenoceptors to increase RSR.     

The effects of dopamine and a low protein diet on glomerular filtration rate and renal plasma flow in the aged kidney

Summary The aims of this study were to determine the effects of dopamine and a low protein diet on glomerular filtration rate and effective renal plasma flow in the aged kidney. Effective renal plasma flow was measured using ¹²⁵I-labelled hippuran and glomerular filtration rate using ⁵¹Cr-labelled EDTA.Low-dose continuous intravenous dopamine 3 g·kg^–1·min^–1 in 10 healthy elderly volunteers caused a significant increase in effective renal plasma flow but not in the mean glomerular filtration rate when compared with baseline. However, glomerular filtration rate did increase substantially in 5 subjects (mean 14.4, SD 1.3). This implied that the elderly kidney was working maximally without reserve capacity in half the elderly. Since renal function is likely to be even more reduced in elderly patients with congestive cardiac failure, dopamine infusions may have little place in this condition in some older patients.A low protein diet (0.69 g·kg^–1) in the same volunteers reduced glomerular filtration rate, suggesting that protein restriction may help to reduce the increased filtration rate in the remaining nephrons, thereby leading to structural and functional preservation in the aged kidney.