Cardiac output and renal blood flow in glycerol-induced acute renal failure in the rat

Occurrence of Low Cardiac Index During Normotensive Periods in Cardiac Surgery: A Prospective Cohort Study Using Continuous Noninvasive Cardiac Output Monitoring

BACKGROUND

Continuous cardiac output monitoring is not standard practice during cardiac surgery, even though patients are at substantial risk for systemic hypoperfusion. Thus, the frequency of low cardiac output during cardiac surgery is unknown.

METHODS

We conducted a prospective cohort study at a tertiary medical center from July 2021 to November 2023. Eligible patients were ≥18 undergoing isolated coronary bypass (CAB) surgery with the use of cardiopulmonary bypass (CPB). Cardiac output indexed to body surface area (CI) was continuously recorded at 5-second intervals throughout surgery using a US Food and Drug Administration (FDA)-approved noninvasive monitor from the arterial blood pressure waveform. Mean arterial blood pressure (MAP) and central venous pressure (CVP) were also analyzed. Low CI was defined as <2 L/min/m2 and low MAP as <65 mm Hg. We calculated time with low CI for each patient for the entire surgery, pre-CPB and post-CPB periods, and the proportion of time with low CI and normal MAP. We used Pearson correlation to evaluate the relationship between CI and MAP and paired Wilcoxon rank sum tests to assess the difference in correlations of CI with MAP before and after CPB.

RESULTS

In total, 101 patients were analyzed (age [standard deviation, SD] 64.8 [9.8] years, 25% female). Total intraoperative time (mean [SD]) with low CI was 86.4 (62) minutes, with 61.2 (42) minutes of low CI pre-CPB and 25.2 (31) minutes post-CPB. Total intraoperative time with low CI and normal MAP was 66.5 (56) minutes, representing mean (SD) 69% (23%) of the total time with low CI; 45.8 (38) minutes occurred pre-CPB and 20.6 (27) minutes occurred post-CPB. Overall, the correlation (mean [SD]) between CI and MAP was 0.33 (0.31), and the correlation was significantly higher pre-CPB (0.53 [0.32]) than post-CPB (0.29 [0.28], 95% confidence interval [CI] for difference [0.18-0.34], P < .001); however, there was substantial heterogeneity among participants in correlations of CI with MAP before and after CPB. Secondary analyses that accounted for CVP did not alter the correlation between CI and MAP. Exploratory analyses suggested duration of low CI (C <2 L/min/m2) was associated with increased risk of postoperative acute kidney injury (odds ratios [ORs] = 1.09; 95% CI; 1.01-1.13; P = .018).

CONCLUSIONS

In a prospective cohort of patients undergoing CAB surgery, low CI was common even when blood pressure was normal. CI and MAP were correlated modestly. Correlation was higher before than after CPB with substantial heterogeneity among individuals. Future studies are needed to examine the independent relation of low CI to postoperative kidney injury and other adverse outcomes related to hypoperfusion.

Administration of a single dose of lithium ameliorates rhabdomyolysis-associated acute kidney injury in rats

Rhabdomyolysis is characterized by muscle damage and leads to acute kidney injury (AKI). Clinical and experimental studies suggest that glycogen synthase kinase 3β (GSK3β) inhibition protects against AKI basically through its critical role in tubular epithelial cell apoptosis, inflammation and fibrosis. Treatment with a single dose of lithium, an inhibitor of GSK3β, accelerated recovery of renal function in cisplatin and ischemic/reperfusion-induced AKI models. We aimed to evaluate the efficacy of a single dose of lithium in the treatment of rhabdomyolysis-induced AKI. Male Wistar rats were allocated to four groups: Sham, received saline 0.9% intraperitoneally (IP); lithium (Li), received a single IP injection of lithium chloride (LiCl) 80 mg/kg body weight (BW); glycerol (Gly), received a single dose of glycerol 50% 5 mL/kg BW intramuscular (IM); glycerol plus lithium (Gly+Li), received a single dose of glycerol 50% IM plus LiCl IP injected 2 hours after glycerol administration. After 24 hours, we performed inulin clearance experiments and collected blood / kidney / muscle samples. Gly rats exhibited renal function impairment accompanied by kidney injury, inflammation and alterations in signaling pathways for apoptosis and redox state balance. Gly+Li rats showed a remarkable improvement in renal function as well as kidney injury score, diminished CPK levels and an overstated decrease of renal and muscle GSK3β protein expression. Furthermore, administration of lithium lowered the amount of macrophage infiltrate, reduced NFκB and caspase renal protein expression and increased the antioxidant component MnSOD. Lithium treatment attenuated renal dysfunction in rhabdomyolysis-associated AKI by improving inulin clearance and reducing CPK levels, inflammation, apoptosis and oxidative stress. These therapeutic effects were due to the inhibition of GSK3β and possibly associated with a decrease in muscle injury.

Pentoxifylline and thiamine ameliorate rhabdomyolysis-induced acute kidney injury in rats via suppressing TLR4/NF-κB and NLRP-3/caspase-1/gasdermin mediated-pyroptosis

Acute kidney injury (AKI) is a common complication of rhabdomyolysis (RM), a syndrome characterized by skeletal muscle damage resulting in renal tubular oxidative stress, inflammation, and activated toll like receptor-4 (TLR-4) and NOD-like receptor protein-3 (NLRP-3) inflammasome. Pyroptosis is a programmed cell death mediated by NLRP-3 leading to the activation of caspase-1 and gasdermin D (GSDMD), the hallmark of pyroptosis. This study aims to investigate the renoprotective effects of two antioxidants; pentoxifylline (PTX) and thiamine (TM) via targeting the aforementioned pathways. RM-AKI was induced in male Albino Wistar rats by intramuscular injection of glycerol (50% v/v, 10 ml/kg). PTX (100 mg/kg, oral) and TM (25 mg/kg, i.p) were administered for 12 days prior glycerol injection and continued for 3 days following induction of RM-AKI. Serum creatinine, blood urea nitrogen (BUN), creatin kinase, lipid peroxides, total antioxidant activity, inflammatory markers (tumor necrosis factor-α, interleukin-1β, and nuclear factor kappa B), TLR4, NLRP-3, caspase-1, GSDMD and c-myc (an apoptotic marker) were estimated. Compared to AKI model, co-administered drugs revealed a significant improvement in renal function and pathology as indicated by the reduction in serum creatinine, BUN and protein cast accumulation. The elevations of oxidative stress, and inflammatory markers as well as the over-expression of c-myc were alleviated. Protein levels of TLR4, NLRP3, cleaved caspase-1, and GSDMD were significantly elevated in RM-AKI model, and this elevation was attenuated by the tested drugs. In conclusion, PTX and TM could be a potential renoprotective approach for patients with RM through targeting TLR4/NF-κB and NLRP-3/caspase-1/gasdermin mediated-pyroptosis pathways.

Effectiveness of deferiprone-loaded nanocarrier in experimentally induced rhabdomyolysis: A dose-comparison study

Herein, the efficacy of free deferiprone (DFP) and DFP-loaded starch/polyethylene glycol/polyacrylic acid (St/PEG/PAAc) nanogel [Nano-DFP] in modulating the biochemical changes induced by glycerol model of rhabdomyolysis (RBD) in male rats was investigated. In this respect, gamma radiation-induced crosslinking was used to produce St/PEG/PAAc nanogel particles, and then, it was used as a nanocarrier for DFP as an attempt to overcome the poor bioavailability and short half-life of DFP. St/PEG/PAAc nanogel was characterized by Fourier transform infrared, dynamic light scattering and Transmission electron microscopy. Free DFP was administered to rats in two doses; 25 and 50 mg following RBD induction, while the loaded nanogel was administered at a dose of 25 mg. The liver and kidney functions were then fully assessed in association with the histological tissue examination of both organs and the femur muscle. Both doses of DFP significantly antagonized the RBD-induced changes in most of the assessed organs functions. The higher dose of DFP, however, showed a statistically more pronounced modulation of RBD effects on each of kidney, liver and skeletal muscles. Nano-DFP; at 25 mg dose, resulted in a statistically significant correction of most of the RBD-related biomarkers with a comparable magnitude to the higher DFP dose rather than the corresponding lower one.

Effect of curcumin on glycerol-induced acute kidney injury in rats

The aim of this study was to investigate the protective role and underlying mechanisms of curcumin on glycerol-induced acute kidney injury (AKI) in rats. Glycerol (10 ml/kg BW, 50% v/v in sterile saline, i.m.) was used to induce AKI, followed by curcumin (200 mg/kg/day, p.o.) administration for 3 days. To confirm renal damage and the effects of curcumin on AKI, serum BUN, Scr, and CK as well as renal SOD, MDA, GSH-Px were measured. Additionally, morphological changes were identified by H&E staining and transmission electron microscopy. The expression of several factors including chemotactic factor MCP-1, proinflammatory cytokines including TNF-α and IL-6, as well as the kidney injury markers, as Kim-1 and Lipocalin-2 were also assessed using q-PCR. Finally, cell apoptosis in renal tissue was detected using in situ TUNEL apoptosis fluorescence staining and expression of proteins associated with apoptotic, oxidative stress and lipid oxidative related signaling pathways were detected using immunohistochemical staining and western blot. The results showed that curcumin exerts renoprotective effects by inhibiting oxidative stress in rhabdomyolysis-induced AKI through regulation of the AMPK and Nrf2/HO-1 signaling pathways, and also ameliorated RM-associated renal injury and cell apoptosis by activating the PI3K/Akt pathway.

Protective effect of quinacrine against glycerol-induced acute kidney injury in rats

BACKGROUND

Acute kidney injury (AKI) is a serious clinical problem with high rate of mortality and morbidity. Currently used prophylactic and therapeutic strategies to address AKI are limited and warrant further studies. In the present study an attempt was made to investigate the effect of quinacrine, a phospholipase A2 inhibitor against glycerol induced AKI in rats.

METHODS

Adult female Wistar rats were divided in to five groups. After 24 h of water deprivation rats in groups 3, 4 and 5 received an intraperitoneal injection of quinacrine (3 mg/kg, 10 mg/kg and 30 mg/kg of body weight respectively). Thirty minutes after the first injection of quinacrine animals in groups 3, 4 and 5 received an intramuscular injection of 25% glycerol (10 ml/kg of body weight). The animals in group 2 received 25% glycerol (10 ml/kg of body weight) only whereas rats in group 1 served as control . The quinacrine administration was continued once daily for three days, on the fourth day animals were sacrificed, blood and kidney were collected for various biochemical and histopathological studies.

RESULTS

Glycerol treatment produced significant renal structural abnormalities and functional impairment (increased urea and creatinine). Increase in myeloperoxidase (MPO) and malondialdehyde (MDA) clearly suggested the involvement of oxidative stress and neutrophilic activity following glycerol administration. Quinacrine dose dependently attenuated glycerol induced structural and functional changes in kidney.

CONCLUSION

The reversal of glycerol induced AKI by quinacrine points towards a role of phospholipase A2 (PLA2) in the pathogenesis of renal injury. The result of this study suggests that quinacrine may offer an alternative mode of treatment for AKI.

Allopurinol attenuates rhabdomyolysis-associated acute kidney injury: Renal and muscular protection

BACKGROUND

Acute kidney injury (AKI) is the most severe complication of rhabdomyolysis. Allopurinol (Allo), a xanthine oxidase inhibitor, has been in the spotlight in the last decade due to new therapeutic applications related to its potent antioxidant effect. The aim of this study was to evaluate the efficacy of Allo in the prevention and treatment of rhabdomyolysis-associated AKI.

METHODS

Male Wistar rats were divided into five groups: saline control group; prophylactic Allo (300mg/L of drinking water, 7 days); glycerol (50%, 5ml/kg, IM); prophylactic Allo + glycerol; and therapeutic Allo (50mg/Kg, IV, 30min after glycerol injection) + glycerol.

RESULTS

Glycerol-injected rats showed markedly reduced glomerular filtration rate associated with renal vasoconstriction, renal tubular damage, increased oxidative stress, apoptosis and inflammation. Allo ameliorated all these alterations. We found 8-isoprostane-PGF_2a (F2-IsoP) as a main factor involved in the oxidative stress-mediated renal vasoconstriction following rhabdomyolysis. Allo reduced F2-IsoP renal expression and restored renal blood flow. Allo also reduced oxidative stress in the damaged muscle, attenuated muscle lesion/inflammation and accelerated muscular recovery. Moreover, we showed new insights into the pathogenesis of rhabdomyolysis-associated AKI, whereas Allo treatment reduced renal inflammation by decreasing renal tissue uric acid levels and consequently inhibiting the inflammasome cascade.

CONCLUSIONS

Allo treatment attenuates renal dysfunction in a model of rhabdomyolysis-associated AKI by reducing oxidative stress (systemic, renal and muscular), apoptosis and inflammation. This may represent a new therapeutic approach for rhabdomyolysis-associated AKI - a new use for an old and widely available medication.

Dual-Purpose Bioreactors to Monitor Noninvasive Physical and Biochemical Markers of Kidney and Liver Scaffold Recellularization

Analysis of perfusion-based bioreactors for organ engineering and a detailed evaluation of physical and biochemical parameters that measure dynamic changes within maturing cell-laden scaffolds are critical components of ex vivo tissue development that remain understudied topics in the tissue and organ engineering literature. Intricately designed bioreactors that house developing tissue are critical to properly recapitulate the in vivo environment, deliver nutrients within perfused media, and monitor physiological parameters of tissue development. Herein, we provide an in-depth description and analysis of two dual-purpose perfusion bioreactors that improve upon current bioreactor designs and enable comparative analyses of ex vivo scaffold recellularization strategies and cell growth performance during long-term maintenance culture of engineered kidney or liver tissues. Both bioreactors are effective at maximizing cell seeding of small-animal organ scaffolds and maintaining cell survival in extended culture. We further demonstrate noninvasive monitoring capabilities for tracking dynamic changes within scaffolds as the native cellular component is removed during decellularization and model human cells are introduced into the scaffold during recellularization and proliferate in maintenance culture. We found that hydrodynamic pressure drop (ΔP) across the retained scaffold vasculature is a noninvasive measurement of scaffold integrity. We further show that ΔP, and thus resistance to fluid flow through the scaffold, decreases with cell loss during decellularization and correspondingly increases to near normal values for whole organs following recellularization of the kidney or liver scaffolds. Perfused media may be further sampled in real time to measure soluble biomarkers (e.g., resazurin, albumin, or kidney injury molecule-1) that indicate degree of cellular metabolic activity, synthetic function, or engraftment into the scaffold. Cell growth within bioreactors is validated for primary and immortalized cells, and the design of each bioreactor is scalable to accommodate any three-dimensional scaffold (e.g., synthetic or naturally derived matrix) that contains conduits for nutrient perfusion to deliver media to growing cells and monitor noninvasive parameters during scaffold repopulation, broadening the applicability of these bioreactor systems.

TNF-α-mediated cardiorenal injury after rhabdomyolysis in rats

The TNF-α serum level increases after rhabdomyolysis and is involved in the subsequent cardiorenal injury. In the present study, we investigated the TNF-α-dependent cell signaling pathways implicated in cellular injury in these organs. Rhabdomyolysis was induced by intramuscular glycerol injection in rats. Renal function, cardiac and renal pathology, and activation of caspases were evaluated during the first 24 h after glycerol injection. TNF-α blockade with infliximab reduced tubular necrosis and cardiorenal apoptosis. Cellular Fas-associated protein with death domain-like IL-1β-converting enzyme inhibitory protein (cFLIP), an inhibitor of caspase-8, was overexpressed in the kidney but not in the heart. The inhibitory effect of cFLIP blunted caspase-8 activation in the kidney. In this condition, the cellular response to the TNF-α stimulus was driven to receptor-interacting protein-1 (RIP1)-mediated necroptosis. Treatment with RIP1 inhibitor (necrostatin-1) isolated or in combination with infliximab showed a similar reduction in tubular necrosis, underscoring the importance of TNF-α-mediated tubular necroptosis in this model. TNF-α played a positive regulatory role in the transcription of proapoptotic Bax and p53-upregulated modulator of apoptosis (PUMA) proteins. Infliximab treatment reduced caspase-9-mediated apoptosis in both organs. Treatment with a caspase-8 inhibitor showed that caspase-8 participated in the process of apoptosis only in the heart, upstream of caspase-9 activation. TNF-α-mediated necroptosis is the predominant form of tubular injury observed in the glycerol model. TNF-α up regulates Bax and PUMA proapoptotic proteins, resulting in activation of the intrinsic pathway of apoptosis in the kidney and heart.

Rhabdomyolysis-induced acute kidney injury under hypoxia and deprivation of food and water

BACKGROUND

To investigate the renal pathophysiologyin rhabdomyolysis-induced acute kidney injury (AKI) in rats under hypoxia and deprivation of food and water (HDFW), thus broadening the knowledge about rhabdomyolysis-induced AKI in massive earthquake.

METHODS

Male Wistar rats weighing 200-230g were randomized into control, rhabdomyolysis (R), HDFW and rhabdomyolysis in combination with HDFW (R/HDFW) group. Experimental rhabdomyolysis rat model was established through clamping hind limb muscles, HDFW model rats were kept in 10% hypoxic chamber unavailable to food and water. At 1, 3, 5, 7, 9, 11d after treatment, serum creatinine (Scr) level, renal index, renal structural changes and cell apoptosis were analyzed.

RESULTS

After R, HDFW, R/HDFW treatment, the animals showed significantly higher Scr levels than the control group. Renal index in R and R/HDFW groups elevated remarkably compared with that in control and HDFW group. The results of histopathology, ultra-structure and apoptosis assay suggested that rhabdomyolysis caused renal tubular injury, HDFW treatment resulted in renal vascular dilation, tissue congestion and tubular cell damage. In addition, more severe renal lesion appeared in R/HDFW.

CONCLUSIONS

We conclude that the association of experimental rhabdomyolysis with HDFW results in a different functional and histological pattern. The rhabdomyolysis-HDFW combination causes more severe renal injury.

Glycerol-induced renal damage improved by 7-O-galloyl-D-sedoheptulose treatment through attenuating oxidative stress

The protective effect of 7-O-galloyl-D-sedoheptulose (GS), isolated from Corni Fructus as an active component, against acute renal failure (ARF) induced by glycerol was investigated. The administration of GS led to a decline in the levels of blood urea nitrogen and creatinine; on the other hand, it did not have a significant effect on creatinine clearance. Furthermore, GS also significantly decreased the urine volume and fractional excretion of sodium, but it increased the urine osmolarity, suggesting the protective role of GS against renal dysfunction. Oxidative stress under ARF was attenuated by GS through the inhibition of lipid peroxidation, scavenging of reactive oxygen species (ROS), and elevation of the antioxidative status. Renal oxidative stress is related to the overproduction of ROS by nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase; therefore, in the present study, the protein expression of p22(phox) and NAD(P)H oxidase-4 (Nox-4) was investigated. GS down-regulated the protein expression of p22(phox); on the other hand, it did not significantly affect the expression of Nox-4. This indicates that GS inhibits the production of superoxide by regulating a component of NAD(P)H oxidase, p22(phox). Furthermore, GS down-regulated the expressions of nuclear factor-κB (NF-κΒ) and inducible nitric oxide (NO) synthase (iNOS), suggesting that GS protects against NO-induced inflammatory pathological conditions under ARF through the regulation of NF-κB and iNOS expressions. The present study indicates that GS exerts a protective effect against ARF through the recovery of renal dysfunction and attenuation of renal oxidative stress by regulating related protein expression.

Fasudil ameliorates rhabdomyolysis-induced acute kidney injury via inhibition of apoptosis

During times of war or natural disasters, rhabdomyolysis leading to acute kidney injury (AKI) can assume epidemic proportions. Fasudil attenuates ischemia/reperfusion-induced AKI. We investigated the therapeutic effect of an early application of fasudil on AKI induced by rhabdomyolysis and explored the potential mechanisms. Male Wistar rats were randomly divided into a control group (saline, 7 mL/kg, i.m.), a Gly group (50% glycerol, 7 mL/kg, i.m.), and a fasudil group (50% glycerol, 7 mL/kg, i.m.; fasudil, 20 mg/kg bodyweight, i.p., three times every 24 h beginning 72 h before glycerol administration). Serum creatinine, blood urea nitrogen (BUN), and histopathological changes were used to demonstrate kidney function 24 h after the glycerol injection. Cell apoptosis and the expression of rho-associated protein kinase member (ROCK1), phosphatase and tensin homolog (PTEN), P-Akt, and caspase-8, -9, and -3 were measured. Serum creatinine and BUN levels increased significantly in Gly group compared with control group. Both levels decreased after fasudil treatment. The renal tubular damage score was significantly lower and cell apoptosis was significantly less in fasudil group compared with Gly group. The expression levels of ROCK1, PTEN, and caspase-8, -9, and -3 were upregulated significantly in Gly group, and their expression was reduced in the fasudil group. The P-Akt level was decreased in Gly group and upregulated significantly in fasudil group. Early application of fasudil reduced rhabdomyolysis-associated renal injury by inhibiting Rho kinase and thereby activating the PI-3K/Akt pathway, which decreased cell apoptosis via both the intrinsic and extrinsic apoptotic pathways.

Attenuation of glycerol-induced acute kidney injury by previous partial hepatectomy: role of hepatocyte growth factor/c-met axis in tubular protection

BACKGROUND/AIMS

Previous partial hepatectomy (HPTX) can attenuate glycerol-induced acute kidney injury (Gly-AKI). The aim of this study was to explore the pathophysiological mechanisms and the role of hepatocyte growth factor (HGF) in kidney protection.

METHODS

Rats were subjected to HPTX 24 h before glycerol administration. Renal function, acute tubular necrosis, apoptosis, leukocyte infiltration, and the expression of HGF, c-met, monocyte chemoattractant protein-1, interleukin-1beta, and heme oxygenase-1 were evaluated 24 h after glycerol injection. The regenerative response was analyzed from 6 to 72 h after glycerol injection (BrdU incorporation). In a separate series of experiments, Gly-AKI+HPTX rats were treated with anti-HGF antibody.

RESULTS

Gly-AKI+HPTX rats showed an increased expression of renal HGF and c-met as well as an improved creatinine clearance and reduced acute tubular necrosis and apoptosis, cytokine expression, and leukocyte infiltration. The regenerative response was less intense 24 and 72 h after glycerol administration in this group. The anti-HGF treatment disclosed an important role of HGF in the reduction of tubular injury, particularly apoptosis. Overexpression of heme oxygenase-1 was observed in Gly-AKI+HPTX rats, but was not associated with HPTX-induced renal protection.

CONCLUSION

We conclude that Gly-AKI+HPTX rats have a reduced susceptibility to renal injury instead of an increased regenerative response and that endogenous HGF overexpression is responsible for suppression of tubular apoptosis.

Adrenomedullin and adrenomedullin binding protein-1 prevent metabolic acidosis after uncontrolled hemorrhage in rats

OBJECTIVE

Management of trauma victims with uncontrolled hemorrhage remains a major problem in combat casualty care at the far-forward battlefield setting. The neuroendocrine response to hemorrhage is to maintain perfusion to the heart and brain, often at the expense of other organ systems. Decreased organ perfusion after hemorrhagic shock is associated with metabolic acidosis, in which the up-regulated endothelin-1 plays an important role. We have recently shown that vascular responsiveness to adrenomedullin (AM), a newly discovered vasodilator peptide, is depressed after hemorrhage and resuscitation. Down-regulation of AM binding protein (AMBP-1) appears to be responsible for this hyporesponsiveness. We therefore hypothesized that administration of AM/AMBP-1 would prevent metabolic acidosis after uncontrolled hemorrhage via down-regulation of endothelin-1.

DESIGN

Prospective, controlled, and randomized animal study.

SETTING

A research institute laboratory.

SUBJECTS

Male Sprague-Dawley rats (275-325 g).

INTERVENTIONS

A rat model of uncontrolled hemorrhage with an extremely low volume of fluid resuscitation was used to mimic the combat situation.

MEASUREMENTS AND MAIN RESULTS

Both lumbar veins of male adult rats were isolated and severed at the junction to the vena cava. The abdomen was kept open but covered with a saline wet gauze for 45 mins and then closed in layers. The animals received 1 mL of normal saline (vehicle) with or without AM (12 microg/kg of body weight) and AMBP-1 (40 microg/kg of body weight) over 45 mins. Various variables were measured at 4 hrs after resuscitation. The bleed-out volumes in the vehicle group and the AM/ AMBP-1 treatment group were 6.78 +/- 0.19 and 6.81 +/- 0.25 mL/rat, respectively. The results indicate that AM/AMBP-1 administration prevented metabolic acidosis, mitigated organ injury, down-regulated preproendothelin-1 gene expression, and decreased plasma levels of endothelin-1 after hemorrhage.

CONCLUSIONS

AM/AMBP-1 may provide a novel approach for the treatment of uncontrolled hemorrhage. The beneficial effect of AM/AMBP-1 is associated with down-regulation of endothelin-1.

Role of caspases on cell death, inflammation, and cell cycle in glycerol-induced acute renal failure

Caspases are the main executioners of apoptosis as well as interleukin (IL)-1beta and IL-18 conversion to active forms. They are activated after acute kidney injuries. In this study, we evaluated the importance of the caspase family in the pathogenesis and recovery of glycerol-induced acute renal failure in rats (Gly-ARF). Rats were treated with pan-caspase or selective caspase 1 and 3 inhibitors at the moment we injected glycerol. Renal function, renal histology (HE), transferase-mediated deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling staining for apoptosis, leukocytes infiltration (immunohistochemistry), renal expression of IL-1beta and IL-18 (immunohistochemistry and Western blot), tubular regeneration (5-bromo-2'-deoxyuridine (BrdU) incorporation), and P27(Kip) expression (Western blot) were evaluated at appropriate times. All inhibitors reduced the renal function impairment. Pan-caspase and caspase-3 inhibitors reduced cellular death (necrosis and apoptosis) 24 h after Gly-ARF. All caspases inhibitors reduced macrophages infiltration. The expression of total IL-1beta was enhanced in Gly-ARF, but the active IL-1beta and IL-18 forms were abolished in pan-caspase treated rats. Caspase-1 inhibitor attenuated Gly-ARF but not tubular injury suggesting glomerular hemodynamic improvement. There was striking regenerative response 48 h after Gly-ARF characterized by enhanced BrdU incorporation and reduced expression of p27(Kip). This response was not blunted by caspases inhibition. Our findings demonstrate that caspases participate in important pathogenic mechanisms in Gly-ARF such as inflammation, apoptosis, vasoconstriction, and tubular necrosis. The early inhibition of caspases attenuates these mechanisms and reduces the renal function impairment in Gly-ARF.

Protective effect of resveratrol, a polyphenolic phytoalexin on glycerol-induced acute renal failure in rat kidney

Rhabdomyolysis-induced myoglobinuric acute renal failure (ARF) accounts for about 10% to 40% of all cases of ARF. Reactive oxygen intermediates have been demonstrated to play an etiologic role in myoglobinuric renal failure. This study was designed to investigate the effect of resveratrol, a polyphenolic phytoalexin in glycerol-induced ARF in rats. Seven groups of rats were employed in this study, group I served as control; group II was given 50% glycerol (8 mL/kg, intramuscularly); groups III IV, and V were given glycerol plus resveratrol (2 mg/kg, 5 mg/kg, and 10 mg/kg p.o. route, respectively) 60 min prior to the glycerol injection; group VI received L-NAME (10 mg/kg, i.p.) along with glycerol and resveratrol (5 mg/kg), group VII animals received L-NAME (10 mg/kg) 30 min prior to glycerol administration. Renal injury was assessed by measuring plasma creatinine, blood urea nitrogen, creatinine, and urea clearance. The oxidative stress was measured by renal malondialdehyde levels and reduced glutathione levels, and by enzymatic activity of catalase, glutathione reductase, and superoxide dismutase. Tissue and urine nitrite levels were measured as an index of total nitric oxide levels. Glycero treatment resulted in a marked decrease in tissue and urine nitric oxide levels, renal oxidative stress, and significantly deranged the renal functions along with deterioration of renal morphology. Pre treatment of animals with resveratrol (5 and 10 mg/kg) 60 min prior to glycerol injection markedly attenuated the fall in nitric oxide levels, renal dysfunction, morphologic alterations, reduced elevated thiobarbituric acid reacting substances, and restored the depleted renal antioxidant enzymes. This protection afforded by resveratrol was significantly reversed by cotreatment of L-NAME along with resveratrol, clearly indicating that resveratrol exerts its protective effect through nitric oxide release along with the antioxidative effect in glycerol-induced ARF.

Protective effect of γ-aminobutyric acid against glycerol-induced acute renal failure in rats

To investigate the effect of gamma-aminobutyric acid (GABA) on acute renal failure, we used a rat model of acute tubular necrosis induced by glycerol. After deprivation of water for 6h, the rats received an injection of 50% glycerol into the muscle of the rear limb at 10 ml/kg body weight. GABA was then administered orally to the rats (100 or 500 mg/kg body weight/day) once every 12h for 3 days. The rats with acute renal failure showed arrested body weight gain and an increase of kidney weight, whereas oral administration of GABA attenuated the physiological changes induced by acute renal failure. However, GABA administration had no significant effect on increased urine volume. Oral administration of GABA at a dose of 100 or 500 mg/kg body weight/day for 3 days significantly improved the markedly elevated levels of blood urea nitrogen and creatinine and the reduced creatinine clearance related to progression of renal failure. Moreover, the rats with acute renal failure exhibited high levels of fractional excretion of sodium (FE(Na)) due to alteration of tubule function following injection of glycerol. However, administration of GABA lowered the FE(Na) levels dose-dependently. Furthermore, urine osmolarity was markedly reduced in control rats with acute renal failure as compared with normal rats, whereas it was significantly increased by administration of GABA at a dose of 500 mg/kg body weight/day. These results indicate that GABA has potential as a therapeutic agent against the renal damage involved in acute renal failure.

Characterization of acute reversible systemic hypertension in a model of heme protein-induced renal injury

In the glycerol model of renal injury we describe an acute rise in systemic arterial pressure which is attended by a reduced vasodilatory response to acetylcholine in vivo; vasodilatory responses to verapamil, however, were not impaired. Neither arginine nor sodium nitroprusside diminished this rise in blood pressure; N(omega)-nitro-L-arginine methyl ester (L-NAME) elevated basal mean arterial pressure and markedly blunted the rise in mean arterial pressure following the administration of glycerol. Aortic rings from the glycerol-treated rat demonstrate an impaired vasodilatory response to acetylcholine, an effect not repaired by arginine; the vasodilatory responses to nitric oxide donors, sodium nitroprusside and SIN-1, were also impaired; 8-bromo-cGMP, at higher doses, evinced a vasodilatory response comparable to that observed in the control rings. This pattern of responses was not a nonspecific effect of aortic injury, since aortic rings treated with mercuric chloride, a potent oxidant, displayed an impaired vasodilatory response to acetylcholine but not to sodium nitroprusside. We conclude that in the glycerol model of heme protein-induced tissue injury, there is an acute elevation in mean arterial pressure attended by impaired endothelium-dependent vasodilatation in vitro and in vivo. We suggest that the acute scavenging of nitric oxide by heme proteins depletes the blood vessel wall of its endogenous vasodilator and permeation of heme proteins into the blood vessel wall may contribute to such sustained effects as observed in vitro.

Effects of nifedipine and platelet activating factor antagonist (BN 52021) in glycerol-induced acute renal failure in rats

We studied the actions of nifedipine and the platelet activating factor (PAF) antagonist BN 52021 on renal and tubular function in glycerol-induced acute renal failure (Gly-ARF). The tubular handling of sodium was evaluated through the lithium clearance method in awake rats in metabolic cages. The sequential analysis of tubular function 3, 6, 12, and 24 h after Gly-ARF showed a sharp decrease in fractional proximal Na reabsorption (FPRNa)--control 74.1 +/- 12.5%, 3 h: 79.5 +/- 6.0%; 6 h: 41.8 +/- 15.9%; 12 h: 22.9 +/- 17.9%; and 24 h: 31.1 +/- 16.2% (p < 0.001) while fractional distal Na reabsorption (FDRNa) did not change during the study. The effect of nifedipine (20 mg/kg p.o.) and BN 52021 (1 mg/kg i.p.) were evaluated 24 h after the induction of Gly-ARF. Both drugs attenuated the reduction in creatinine clearance (control 431.8 +/- 108.2, glycerol 96.7 +/- 43.8, glycerol plus nifedipine 264.9 +/- 103.5, and glycerol plus BN 52021 188.9 +/- 69.8 microL/min/100 g, p < 0.001). However, only nifedipine could keep FPRNa higher than untreated rats (58.3 +/- 13.2 vs. 31.1 +/- 16.2%, p < 0.05) and reduced the tubular necrosis on histologic semiquantitative analysis. Our data showed that nifedipine and BN 52021 could protect against filtration failure in Gly-ARF but that only nifedipine reduced the proximal tubular lesion.

Early detection of acute tubular injury with diffusion-weighted magnetic resonance imaging in a rat model of myohemoglobinuric acute renal failure

We evaluated the feasibility of magnetic resonance imaging (MRI) for early detection of tubular injury by monitoring changes in the apparent diffusion coefficient (ADC) of renal water in a rat model of myohemoglobinuric glycerol-induced acute renal failure (ARF). Diffusion-weighted MRI was performed concurrently with measurements of serum creatinine and blood urea nitrogen (BUN), evaluation of renal perfusion with dynamic contrast-enhanced MRI, and renal morphological examination. ADC values in the cortex and outer medulla significantly declined within minutes after the glycerol administration (70-75% of control at 4 min and 50-60% of control at 15 min). Contrast-enhanced MRI demonstrated renal hypoperfusion at 20 min after the onset of injury. Light microscopy showed normal glomeruli and edematous tubular epithelial cells at 10 and 30 min, with more severe swelling and protein casts at 30 min. No changes in serum creatinine or BUN levels were detected. We hypothesize that decrease in renal ADC may be attributed to renal ischemia and to subsequent intracellular accumulation of diffusion-restricted water. Similar imaging evaluation in other experimental models of ARF, and in patients, will define the diagnostic value of renal ADC changes in early detection of acute tubular injury.

USPIO-enhanced MR imaging of glycerol-induced acute renal failure in the rabbit

Enhanced-MR imaging in combination with ultrasmall superparamagnetic iron oxide (USPIO) was used in the glycerol-induced model of acute renal failure (ARF) in the rabbit to detect renal perfusion abnormalities. A control group (n = 5) and an ARF group (n = 5) were studied after intramuscular injection of glycerol (10 ml/kg) with T2-weighted spin-echo sequence at 1.5 T and a 27 mumol/kg IV dose of iron. The signal intensity (SI) was quantified in the cortex, the outer medulla (OM), and the inner medulla (IM). In control rabbits, the maximum SI decrease after USPIO injection was in the OM (76% +/- 3.6), as this is the region of maximal vascular density, then in the IM (73.4% +/- 2.9). In the glycerol group, SI loss in the OM (61% +/- 12.6) and the IM (45.2% +/- 16.24) was significant less than in the control group (p < .05). Pathology results showed fibrinous thrombus in the efferent arterioles and congestive aspect of the vasa recta in the medulla. We argue that a reduced medullary concentration of USPIO in the renal failure group is indicative of medullary hypoperfusion.

Models of glycerol-induced acute renal failure in rats

Acute renal failure (ARF) following rhabdomyolysis is not uncommon in man. The popular model for ARF formation following rhabdomyolysis in experimental animals is glycerol injection into the leg muscle following a 24 hour period of water deprivation. A large percentage of patients developing ARF following rhabdomyolysis do not suffer from such long periods of water deprivation. On the contrary, fluid loss in patients developing ARF is relatively fast and is the result of excessive sweating or hemorrhage. Since it is known that the hydration state of the body during rhabdomyolysis considerably affects the development of ARF, it seems that the popular model of glycerol injection following a prolonged period of water deprivation in experimental animals is, to a certain extent, deficient. The aim of the present study was to examine two models of ARF formation in the rat following glycerol injection and acute diminution of the body's water content: 1) by sucrose injection (200 mg/100 g), 2) by hemorrhage (0.7 ml/100 g). A number of differences were found between the various models of ARF formation by glycerol. The differences are mainly expressed in the urine volume three hours after the glycerol injection. In the sucrose and hemorrhage groups a decrease of 29% and 66% (p < 0.001) in urine volume was found at the end of the experiment. In contradistinction, in the group that underwent water deprivation for a period of 24 hours prior to the glycerol injection, an increase of 46% (p < 0.001) in the urine volume was observed at the end of the experiment. Differences were also found in potassium uptake and in the extent of the decrease in renal cortex blood flow as measured by the laser Doppler flowmetry technique. From this study it may be concluded that glycerol injection to the rat leg muscle results in ARF in all three methods of decreasing the body's fluid content. It is possible that the models of sucrose injection or hemorrhage prior to glycerol injection are better suited for reflecting the hydration condition of humans suffering from rhabdomyolysis than 24 hours of water deprivation prior to this injection.

Glycerol induced ARF in rats is mediated by tumor necrosis factor-alpha

Glycerol-induced acute renal failure (ARF) in rats is a model of acute trauma in which intra-muscular injection of 50% glycerol causes rapid myoglobinuria, oliguria, and a rapid reduction in glomerular filtration rate. We found that plasma tumor necrosis factor-alpha (TNF-alpha) is rapidly induced in glycerol injected rats. It can be detected in some animals as early as 30 minutes post-injection, peaks at one hour (range: 4 to 32 U/ml) with no significant difference between blood from renal vein and vena cava, and decreases by three hours. None was detected in control saline injected rats (P < 0.001). Four out of five rats infused with neutralizing anti-TNF-alpha antiserum (200 microliters/300 g body wt) immediately prior to glycerol injection had significantly protected kidney function (P = 0.001). In these rats, plasma urea (104.8 +/- 58.9 mg%) and creatinine (1.16 +/- 0.38 mg%) were lower and creatinine clearance higher (0.34 +/- 011 ml/min) than in glycerol injected animals pretreated with normal serum (291.8 +/- 41.8 mg%, 3.15 +/- 0.74 mg%, and 0.03 +/- 0.03 ml/min, respectively) or animals injected with glycerol alone (302.6 +/- 76.8 mg%, 3.45 +/- 0.97 mg%, and 0.03 +/- 0.03 ml/min, respectively). These results imply a direct role for TNF-alpha in pathogenesis of glycerol induced ARF in rats.

MR imaging of blood oxygenation-dependent changes in focal renal ischemia and transplanted liver tumor in rat

The potential of using fast magnetic resonance (MR) imaging in conjunction with apnea-induced blood deoxygenation for the noninvasive monitoring of relative perfusion in the rat abdomen has been studied with two experimental models: glycerol-induced focal renal ischemia and transplanted liver tumor. Gradient-echo echo-planar imaging (GRE-EPI) (TE of 20 msec at 2T) of liver and kidney was performed before, during, and after a 60-second apnea episode and then was followed in the same rat by contrast-enhanced (a) GRE-EPI and (b) T1-weighted spin-echo imaging (TR msec/TE msec = 200/6) with polylysine-(gadolinium-DTPA [diethylenetriaminepentaacetic acid]). The results indicate that a noninvasive vascular challenge due to apnea can be used for the detection of focal tissue perfusion abnormalities in rat kidney and liver tumor.

Detection of zonal renal ischemia with contrast-enhanced MR imaging with a macromolecular blood pool contrast agent

The potential of magnetic resonance (MR) imaging enhanced with albumin-(gadolinium diethylenetriaminepentaacetic acid [DTPA])35, a macromolecular blood pool marker, for detection of focal changes in renal perfusion was studied in a myoglobinuric acute renal failure (ARF) model in the rat. T1-weighted spin-echo postcontrast images of injured kidneys at 3 hours after glycerol injection showed three distinct zones: a strongly enhanced outer cortex, a low-intensity inner cortex, and a strongly enhanced medulla. The distinct band of low intensity in the inner cortex indicated zonal decreased blood volume, corresponding to published microsphere data showing zonal low perfusion in the inner cortex. Contrast differences between parenchymal zones were significant for at least 30 minutes. No focal ischemic changes could be delineated on nonenhanced images. Enhanced and nonenhanced images of injured kidneys obtained at 24 hours after glycerol injection revealed no zonal differentiation. Contrast-enhanced MR imaging data in this ARF model correlated well with pathologic data and microsphere perfusion results. Contrast-enhanced characterization of the ischemic phase of renal injury with MR imaging may improve specificity for the diagnosis of ARF and may serve as a marker for therapeutic intervention.

Decrease of catecholamine and neuropeptide Y-like immunoreactivity in the glycerol-induced acute renal failure of rats

Changes of catecholamine and neuropeptide Y (NPY) were investigated in experimental acute renal failure (ARF) of rats. Concentrations of noradrenaline (NA) and dopamine (DA) were determined by chromatographic analysis using electrochemical detection. Renal content of NPY, identified by radioimmunoassay, was expressed as NPY-like immunoreactivity (NPY-LI). All animals with a plasma urea value higher than 200 mg/dl induced by injection of glycerol were employed as ARF subjects for the experiment. Formation of ARF was also confirmed by histological findings showing diffused necrosis of tubular epithelia. In ARF rats, renal contents of NA and DA decreased markedly (P less than 0.001), NA (ng/g wet tissue) decreased from 186.3 +/- 19.6 to 2.81 +/- 0.67 (n = 8), and DA (ng/g wet tissue) decreased from 14.69 +/- 4.97 to 4.05 +/- 2.66 (n = 8). Similarly, NPY-LI (pg/g wet tissue) in ARF was reduced significantly (P less than 0.001) from 435.23 +/- 35.82 to 4.61 +/- 0.52 (n = 8). The decrease of NA in ARF was obtained parallel to the change of NPY-LI; degeneration of adrenergic nerve fibers was confirmed by immunohistochemical observation. Results obtained suggest damage to the adrenergic and the dopaminergic innervation in the kidneys during ARF.

The protective mechanism of thyroidectomy in a rat model of chronic renal failure

Selective thyroidectomy (Tx) has been shown to attenuate proteinuria and disease progression in models of chronic renal failure (CRF). In this investigation, four groups of Munich-Wistar rats were studied to determine if glomerular dynamics or another renal metabolic consequence of Tx was responsible for the protective effect as measured by 24-hour protein excretion (UPROT). The groups were TxT4, thyroxine-replaced Tx rats with five-sixths nephrectomy; Tx, Tx rats not receiving replacement thyroxine with five-sixths nephrectomy; TxI, Tx rats not receiving replacement thyroxine with five-sixths nephrectomy that were given continuous intraperitoneal isoproterenol to restore systemic and renal hemodynamics; and TxT4(C), two-kidney Tx rats receiving replacement thyroxine that served as normal controls. Five-sixths nephrectomy was carried out 2 weeks after Tx, and experiments were carried out 1 week later. Serum T4 was profoundly reduced and there was failure to gain weight in Tx and TxI rats, despite similar protein intakes in all groups. Cardiac output was reduced in Tx, but was similar in TxI to levels in TxT4 rats. Whole-kidney glomerular filtration rate was lower in Tx, at 0.145 +/- 0.052 mL/min (P less than 0.05), but similar in TxI (0.305 +/- 0.147 mL/min) to that in TxT4 rats (0.317 +/- 0.135 mL/min). Twenty-four-hour urinary protein, which was 129 +/- 57 mg in TxT4, was reduced in Tx to 9 +/- 3 mg (P less than 0.01) but restored in TxI to 89 +/- 30 mg, a level similar to that in TxT4.(ABSTRACT TRUNCATED AT 250 WORDS)

Amelioration of glycerol-induced acute renal failure in the rat with 8-phenyltheophylline: timing of intervention

The importance of timing and duration of 8-phenyltheophylline (8-PT) administration in determining its beneficial action in glycerol-induced acute renal failure (ARF) was investigated by examining the effects of a single dose of 8-PT given immediately following (0 h) glycerol injection and at 1 and 3 h after glycerol injection. 8-PT when given at 0 h significantly lowered plasma urea and creatinine concentrations and significantly increased inulin clearance when compared both to untreated animals and those that received the vehicle for the drug. By contrast, 8-PT when administered at 1 h afforded no protective effect on renal function and, when injected at 3 h, the only significant effect was lowered plasma creatinine levels when compared to untreated rats; at this latter time it did not lower plasma urea levels or improve inulin clearance. None of the 8-PT injections attenuated the increase in kidney weight associated with ARF or reduced the kidney damage as assessed by histological examination. The results show that a single administration of 8-PT made immediately following glycerol injection can ameliorate the biochemical and functional indices of impaired renal function, but does not produce an improvement in kidney morphology.

Proton magnetic resonance in experimental acute and chronic renal failure in rats

Kidney cortical and medullary "spin-lattice" (T1) and "spin-spin" (T2) relaxation times were measured by spectroscopy in several types of experimental renal failure in rats. The T1 and the measured tissue water content were used to calculate the fraction bound (FB) and hydration fraction (HF) according to a fast proton diffusion model. The present study demonstrated the possibility to differentiate between normal and pathological renal tissue resulting from renal artery clamping (RAC), renal pedicle clamping (RPC) with or without reflow, glycerol-induced acute renal failure with or without previous dehydration, and chronic hypertensive renal failure induced by 5/6 nephrectomy and saline loading, with low (6%) or normal (21%) protein diet. Shortened T1 and prolonged T2 found in both cortex and medulla of the glycerol-induced ARF in dehydrated rats seem to represent a MR ischemic pattern. The prolongation of T1 and T2 and the increase in water content in the other groups seem to relate to different amounts of tubular obstruction and renal congestion. In summary, characteristic MR properties of different types of renal failure may provide etiological and pathogenetic diagnostic possibilities.

Selective inhibition of thromboxane synthesis in glycerol-induced acute renal failure

It has recently been postulated that thromboxane A2 may participate in the pathogenesis of acute myohemoglobinuric experimental acute renal failure. To investigate this further, the effect of selective inhibition of thromboxane synthesis on the course of glycerol-induced acute renal failure was determined. Despite significant inhibition of thromboxane synthesis by 4-imidazole-yl-acetophenone, the functional and morphologic disturbance induced by glycerol was unaltered. Moreover, pretreatment with 4-imidazole-yl-acetophenone failed to prevent the fall in renal blood flow seen following glycerol administration. These results argue against a major role for thromboxane A2 in the pathogenesis of this form of experimental acute renal failure.

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. 9 The protective effect of 8-PT in rats with ARF was probably the result of adenosine antagonism.

Proton MR study of different types of experimental acute renal failure in rats

Kidney cortical and medullary spin-lattice (T1) and spin-spin (T2) relaxation times were measured in several types of experimental acute renal failure in rats with a Bruker PC "Multispec." Gentamicin ARF was obtained after one i.p. injection of 100mg Gentamicin/kg BW/day for 8 days. Glycerol ARF: 24 hours after one i.m. injection of 10 ml 50% Glycerol/kg BW. Obstruction ARF: 3 days after complete ureteral ligation. Renal tissue total water content, hydration fraction, fraction bound, blood urea and creatinine were measured at the end of the experiments. Shortened T1 and prolonged T2 were found in both cortex and medulla in the Glycerol ARF group. Gentamicin renal toxicity and the non-functioning kidney with ureteral obstruction are characterized by significant prolongation of T1 and T2 in cortex, while the medullary T1 and T2 were prolonged only in obstruction ARF. The highest T1 and T2 were found in the obstructed non-functioning kidney. The total water content decreased in the Glycerol ARF, increased in the obstruction and remain unchanged in Gentamicin ARF. The hydration fraction and the fraction bound changed significantly in the opposite direction with the total water content. Different profiles of renal cortical and medullary magnetic resonance properties found in several models of experimental ARF in rats indicate that MR properties may provide etiopathogenetic diagnostic possibilities.

Effect of cyclosporine administration on renal hemodynamics in conscious rats

The effect of acute and chronic administration of cyclosporine on systemic and renal hemodynamics was studied in conscious rats. Infusion of cyclosporine in a dose of 20 mg/kg (Cy 20) resulted in a significant fall in renal blood flow (RBF) (3.4 vs. 6.5 ml/min/g, P less than 0.05) and a rise in renal vascular resistance (RVR) (36.9 vs. 20.6 mm Hg/ml/min/g, P less than 0.05). Infusion of cyclosporine at a dose of 10 mg/kg (Cy 10) did not result in a significant change in RBF or RVR. Both doses of cyclosporine resulted in stimulation of plasma renin activity (PRA) from control values of 5.6 +/- 0.8 ng/ml/hr to 11.6 +/- 2.0 with 10 mg/kg and 26.7 +/- 5.6 with 20 mg/kg. Urinary 6-keto-PGF1 alpha excretion increased from control values of 14.0 +/- 2.0 ng/6 hr to 22.7 +/- 2.2 with 10 mg/kg and 25.0 +/- 2.0 with 20 mg/kg. Similar effects on RBF, RVR, PRA, and 6-keto-PGF1 alpha excretion were seen after chronic administration of cyclosporine (20 mg/kg i.p. for 7 days). Pretreatment of animals with captopril did not prevent the fall in RBF after cyclosporine, suggesting that the vasoconstriction was not mediated by angiotensin II. Animals treated with meclofenamate demonstrated reduction in RBF with 10 mg/kg cyclosporine (4.3 vs. 7.0 ml/min/g, P less than 0.05), suggesting that prostaglandins protect against the vasoconstrictor effect of cyclosporine. Administration of phenoxybenzamine after cyclosporine improved RBF (5.0 vs. 3.4 ml/min/g) and restored RVR to normal. Similarly, renal denervation dramatically reduced the fall in RBF after cyclosporine (innervated right kidney 3.6 vs. denervated left kidney 6.0 ml/min/g, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of perinatal asphyxia and myoglobinuria on development of acute, neonatal renal failure

Thirty four consecutive neonates with birth asphyxia or respiratory problems were examined in the first week of life to clarify the relation between neonatal myoglobinuria and acute renal failure. Investigations included determination of creatinine clearance, fractional sodium excretion, and N-acetyl-beta-D glucosaminidase index as an indicator of tubular injury. The infants' gestational ages ranged from 29 to 41 weeks (mean 36 weeks). Fifteen infants did not have myoglobinuria on the first day of life (group A); myoglobinuria was mild in eight infants (group B) and severe in eleven (group C). Two infants in group B and seven in group C developed acute renal failure (47%). Ten infants in group C (91%) had severe asphyxia, five of whom (45%) also suffered neonatal seizures and intracranial haemorrhage. We suggest that myoglobin derived from muscle breakdown in asphyxiated infants may lead to acute renal failure secondary to a reduction in renal blood flow, or to tubular damage.

Hemodynamic basis for human acute renal failure (vasomotor nephropathy)

Oliguric acute renal failure in man is characterized by intense outer cortical vasoconstriction and a marked increase in preglomerular resistance. The degree of preglomerlar resistance change needed to cause the expected 50 to 80 percent fall in blood flow far exceeds the level that would totally abolish filtration. By contrast, equal 3.0-fold increases in both pre- and postglomerular resistance provide this same degree of ischemia but leave filtration very well maintained. Such a scenario seems unlikely, however, since it would entail a mere 15 to 25 percent decrease in preglomerular resistance vessel caliber rather than the extreme attenuation observed. By contrast, there are reasons to believe that preglomerular constriction may be accompanied by postglomerular vascular relaxation. In sum, unless cortical ischemia reflects precisely matched increases in pre- and postglomerular resistances, filtration failure is inevitable in human vasomotor nephropathy.

Cardiovascular responses in rats with glycerol-induced acute renal failure

Autonomic and cardiovascular function were assessed in rats with glycerol-induced acute renal failure (ARF). Rats with ARF had significantly lower mean arterial blood pressure and heart rates and significantly elevated plasma noradrenaline concentrations. The chronotropic responses to right cervical sympathetic and vagal stimulation were diminished in rats with ARF. The pressor and depressor responses to noradrenaline and nitroprusside respectively when expressed as a change in mmHg pressure were significantly reduced in rats with ARF when compared to controls. However, when the depressor responses to nitroprusside were expressed as a percentage fall in basal mean arterial pressure, with the exception of the response to a dose of 10 micrograms kg-1, there were no significant differences between control and uraemic rats. The present findings show that in the rat, changes in cardiovascular responsiveness occur after a brief period of uraemia which are similar to those observed in patients and rats with chronic renal failure.

Control of renal hemodynamics and glomerular filtration rate in chronic hypercalcemia. Role of prostaglandins, renin-angiotensin system, and calcium

The role of prostaglandins (PG), renin-angiotensin system (RAS) and calcium (Ca) in the control of renal hemodynamics and glomerular filtration rate (GFR) in chronic hypercalcemia (serum Ca 12.8 mg%) was studied. Renal blood flow (RBF, 6.39 ml/min per gram kidney weight [gkw]) and GFR (0.52 ml/min per gkw) were significantly decreased in hypercalcemic rats when compared with normocalcemic rats (7.15, P < 0.001 and 0.74, P < 0.05, respectively). These changes in RBF and GFR occurred independent of any significant alterations in systemic hemodynamics, blood and plasma volume. Inhibition of the renal PG with indomethacin resulted in marked decrements in both RBF (6.39-4.12 ml/min per gkw, P < 0.01) and GFR (0.52-0.19 ml/min per gkw, P < 0.01) in hypercalcemic rats, whereas there was no significant alterations in normocalcemic rats. Inhibition of the RAS with captopril resulted in marked increments in both RBF (6.39-7.35 ml/min per gkw, P < 0.05) and GFR (0.52-0.74 ml/min per gkw, P < 0.05) in hypercalcemic rats. In fact, there was no significant difference from the RBF and GFR of similarly treated normocalcemic rats. Similar results were also obtained with the competitive angiotensin II (AII) antagonist (sarcosyl(1)-isoleucyl(5)-glycyl(8)) AII. Since both the renal PG and the RAS are involved in the control of RBF and GFR in hypercalcemia, the role of each is best revealed in the absence of the other. Hence, comparison of the RBF and GFR in the PG-inhibited hypercalcemic rats in the presence of AII (4.12 and 0.19 ml/min per gkw, respectively) and absence of AII (5.99 and 0.53 ml/min per gkw, P < 0.01 for both) reveals the vasoconstrictive role for AII in hypercalcemia. On the other hand, comparison of the RBF and GFR in the AII-inhibited hypercalcemic rats in the presence of PG (7.35 and 0.74 ml/min per gkw, respectively) and absence of PG (5.99 and 0.53 ml/min per gkw, P < 0.01 and P < 0.05, respectively) reveals the vasodilatory role for PG in hypercalcemia. Finally, comparison of the RBF and GFR in both PG- and AII-inhibited hypercalcemic rats (5.99 and 0.53 ml/min per gkw, respectively) with similarly treated normocalcemic rats (7.30 and 0.94 ml/min per gkw, P < 0.001 and P < 0.005, respectively) reveals the vasoconstrictive role for Ca in chronic hypercalcemia. Our study therefore demonstrates that in chronic hypercalcemia the RBF and GFR are controlled by an active interplay of the vasoconstrictive effect of AII, the vasodilatory effect of renal PG, and the direct vasoconstrictive effect of Ca, independent of either AII or PG. The sum total of these forces produces a modest but significant decrease in RBF and GFR.

Dissociation of glomerular filtration and renal blood flow in HgCl2-induced acute renal failure

This study evaluates the role of early renal vasoconstriction in the pathogenesis of mercuric chloride (HgCl2)-induced acute renal failure (ARF) in the dog. Within 3 hr after mercury, glomerular filtration rate (GFR), from 45 +/- 4 25 +/- 2 ml/min, and renal blood flow (RBF), from 268 +/- 22 to 161 +/- 19 ml/min, decreased simultaneously. A rise in diuresis and urinary solute excretion occurred. Morphological and functional studies excluded a major role for tubular leakage or obstruction. An attempt was made to prevent the early renal vasoconstriction, by the administration of Haemaccel, a plasma volume expander, alone or in combination with phentolamine. In both settings the fall in RBF after mercury was prevented. Haemaccel volume expansion alone provoked a significant rise in GFR before HgCl2, but the GFR fell by 29% 3 hr after HgCl2. The Haemaccel/phentolamine combination had no influence on pre-mercury GFR values. In this group, a decrease of GFR by 44% was noted 3 hr after mercury. In conclusion, changes in GFR and renal hemodynamics can be dissociated in the early phase of nephrotoxic ARF. The fall in GFR can be attributed either to a decrease in glomerular ultrafiltration capacity and/or changes in glomerular afferent and efferent resistances, leading to a decrease in glomerular hydrostatic pressure.

Mechanism of the decreased renal blood flow in the potassium-depleted conscious rat

Although chronic potassium deficiency is a common clinical problem, the hemodynamic consequences of chronic sustained potassium depletion have not been clearly delineated. In this study, the hemodynamic consequences of chronic potassium depletion were evaluated in the conscious rat. Potassium-depleted rats had a decrease in mean arterial pressure which was caused by a decrease in systemic vascular resistance. In association with these changes in systemic hemodynamics, renal blood flow (RBF) was also decreased. The decreased renal blood flow was caused by an increased renal vascular resistance (RVR). Because plasma renin activity was increased the role of angiotensin II as a renal vasoconstrictor was evaluated by utilizing two angiotensin antagonists. Although the administration of saralasin to potassium-depleted rats did not alter systemic hemodynamics, RVR was decreased and RBF was increased. Similar results were obtained with the converting enzyme inhibitor teprotide. Because products of endoperoxide metabolism may cause renal vasoconstriction, the role of prostaglandins and thromboxanes as renal vasoconstrictors were evaluated by utilizing cyclo-oxygenase and thromboxane synthetase inhibitors. None of these agents altered systemic hemodynamics. Following the administration of indomethacin, RVR was decreased and RBF was increased in potassium-depleted rats. Similar results were obtained with another cyclo-oxygenase inhibitor, meclofenamate, and with imidazole, an inhibitor of thromboxane synthetase. Because neither angiotensin II nor products of endoperoxide metabolism could alone account for the increased renal vascular resistance of potassium depletion, studies were performed in potassium-depleted rats treated with indomethacin plus either saralasin or teprotide. In these potassium-depleted animals, renal blood flow was restored to normal. In conclusion, the decrease in renal blood flow and the increase in renal vascular resistance in potassium depletion is mediated by angiotensin II and a product of prostaglandin endoperoxide metabolism, most likely, thromboxane.

Role of vasopressin in the impaired water excretion of glucocorticoid deficiency

The mechanism whereby glucocorticoid deficiency impairs renal water excretion was studied in the conscious mineralocorticoid-replaced, adrenalectomized rat. Control animals received physiologic replacement with prednisolone, and experimental animals were deprived of glucocorticoid hormone for either 1 or 14 days. The control animals excreted 95 +/- 1.9% of an acute water load (30 ml/kg) in 3 hours, a value significantly higher than the volume excreted by animals deprived fo glucocorticoid hormone for 1 day (70.0 +/- 3.6%, P less than 0.01) and 14 days (40.0 +/- 3.9%, P less than 0.01). Following the acute water load, plasma vasopressin levels, as measured by radioimmunoassay, was 1.08 pg/ml in the control rats, a value significantly lower than values obtained after the water load in rats deprived of glucocorticoid hormone for 1 day (2.5 +/- 0.2 pg/ml, P less than 0.01) and 14 days (2.4 +/- 0.3 pg/ml, P less than 0.01). To further examine the effect of plasma vasopressin in the impaired water excretion of glucocorticoid deficiency, we performed studied in Brattleboro rats with central diabetes insipidus. In these animals with absence of vasopressin, a defect in water excretion was observed after 14 days, but no 1 day, of glucocorticoid deficiency. In Sprague-Dawley rats, the impaired water excretion after 14 days of glucocorticoid deficiency was associated with a significantly lower cardiac index (209 +/- 14 vs. 291 +/- 11 ml/min/kg, P less than 0.01) and renal blood flow (3.8 +/- 0.3 vs. 5.7 +/- 0.2 ml/min/g, P less than 0.01) than that observed after 1 day of glucocorticoid deficiency. In diabetes insipidus rats, after 14 days of glucocorticoid deficiency, the percentage of an acute water load excreted (121 +/- 7% vs. 158.7 +/- 7.0%, P less than 0.01) was lower than that observed after 1 day of glucocorticoid deficiency. In summary, the present results indicate that glucocorticoid deficiency impairs renal water excretion by both vasopressin-dependent and vasopressin-independent mechanisms. The vasopressin-dependent renal mechanism is associated with a marked decrease in both systemic and renal hemodynamics.

Mechanisms of altered renal perfusion in the early stage of obstructive jaundice

Mechanisms responsible for renal hemodynamic alterations were studied in jaundiced (by bile-duct ligation) rabbits (BDL) 10 days after ligation of the biliary tract, in comparison with sham-operated rabbits (SO). Arterial hematocrit, plasma volume, blood pressure, abdominal inferior vena cava pressure, and heart rate were not significantly different between the BDL and SO groups. Cardiac output in BDL rabbits decreased to approximately 73% of the value for SO rabbits. Renal blood flow and GFR were reduced to 64 and 61%, respectively. Reductions in blood pressure and renal blood flow, caused by bleeding (8 ml/kg of body wt), were more marked in the BDL group than they were in the SO group. In the BDL group, the recovery of blood pressure following blood infusion was slower and the mortality was higher, There was no significant increase in the renovascular sensitivity to exogenous noradrenaline or angiotensin II in the BDL group. The findings indicate that the early stage of obstructive jaundice in rabbits was characterized by altered renal perfusion partly due to reduced cardiac output and by incrased liability to hemorrhagic hypotension.