The role of dexamethasone in scorpion venom-induced deregulation of sodium and water transport in rat lungs

BACKGROUND

Severe scorpion envenomation can evolve to lung injury and, in some cases, death. The lung injury could be attributed to acute left ventricular failure and increased pulmonary vascular permeability secondary to the release of inflammatory mediators. In clinical practice, corticosteroids have been administered to reduce the early side effects of the anti-venom. We propose to study the effects of Tityus serrulatus venom and dexamethasone on pulmonary expression of sodium and water transporters, as well as on the inflammatory response.

METHODS

Wistar rats were injected intraperitoneally with saline (control group), dexamethasone, and saline (2.0 mg/kg body weight-60 min before saline injection; dexamethasone + saline group), venom (T. serrulatus venom-3.8 mg/kg body weight), or dexamethasone and venom (2.0 mg/kg body weight-60 min before venom injection; dexamethasone + venom group). At 60 min after venom/saline injection, experiments were performed in ventilated and non-ventilated animals. We analyzed sodium transporters, water transporters, and Toll-like receptor 4 (TLR4) by Western blotting, macrophage infiltration by immunohistochemistry, and serum interleukin (IL) by cytokine assay.

RESULTS

In the lung tissue of non-ventilated envenomed animals, protein expression of the epithelial sodium channel alpha subunit (α-ENaC) and aquaporin 5 (AQP5) were markedly downregulated whereas that of the Na-K-2Cl cotransporter (NKCC1) and TLR4 was elevated although expression of the Na,K-ATPase alpha 1 subunit was unaffected. Dexamethasone protected protein expression of α-ENaC, NKCC1, and TLR4 but not that of AQP5. We found that IL-6, IL-10, and tumor necrosis factor alpha were elevated in the venom and dexamethasone + venom groups although CD68 expression in lung tissue was elevated only in the venom group. Among the ventilated animals, both envenomed groups presented hypotension at 50 min after injection, and the arterial oxygen tension/fraction of inspired oxygen ratio was lower at 60 min than at baseline.

CONCLUSIONS

Our results suggest that T. serrulatus venom and dexamethasone both regulate sodium transport in the lung and that T serrulatus venom regulates sodium transport via the TLR4 pathway.

Iohexol clearance for determination of glomerular filtration rate in rats induced to acute renal failure

INTRODUCTION

The glomerular filtration rate (GFR) is considered an especially important tool for the measurement of renal function. Inulin clearance (InCl) is the classic reference method for this purpose, although it is associated with a number of disadvantages; thus, other markers have been proposed, including iohexol. Determination of iohexol clearance (IoCl) has been established for clinical use; however, its application as a GFR marker in experimental rat models has not been reported.

OBJECTIVES

This study aims to standardize a methodology for the measurement of iohexol clearance and to evaluate its applicability as a marker of GFR in rats with induced toxic acute renal failure (ARF), using InCl as the gold standard.

MATERIALS AND METHODS

Twenty-six Wistar male rats (200-300 g) were divided into the following two groups: a control group (n=7) and an ARF group (n=19). ARF was induced by the subcutaneous administration of cisplatin (5 mg/kg); IoCl and InCl were determined simultaneously, and plasma creatinine (pCreat) dosage was measured colorimetrically.

RESULTS

The pCreat, InCl and IoCl levels were consistent with the expected values for the renal function ranges of the evaluated animals, and the IoCl and InCl levels were significantly correlated (r=0.792). An inverse moderate linear correlation between the IoCl and pCreat measurements (r=-0.587) and between the InCl and pCreat measurements (r=-0.722) were observed.

CONCLUSION

These results confirm a correlation between IoCl and the gold standard of GFR, InCl measurement. IoCl offers a relevant advantage over InCl because determination of the former allows the animal to live after the procedure.

Effect of creatine supplementation on measured glomerular filtration rate in postmenopausal women

We aimed to investigate whether creatine supplementation affects the measured glomerular filtration rate in postmenopausal women (age, 58 ± 3 years). Subjects were randomly assigned to receive either creatine (20 g·day–1 for 1 week and 5 g·day–1 thereafter) or a placebo. Kidney function was assessed at baseline and after 12 weeks. [51Cr]EDTA clearance remained unchanged (CR-PRE: 86.16 ± 14.36 mL·min–1 per 1.73 m2, POST: 87.25 ± 17.60 mL·min–1 per 1.73 m2; PL-PRE: 85.15 ± 8.54 mL·min–1 per 1.73 m2, POST: 87.18 ± 9.64 mL·min–1 per 1.73 m2; p = 0.81). Thus, we concluded that creatine supplementation does not affect glomerular filtration rate in postmenopausal women.

Mesenchymal stem cells attenuate renal fibrosis through immune modulation and remodeling properties in a rat remnant kidney model

Mesenchymal stem cells (MSCs) have regenerative properties in acute kidney injury, but their role in chronic kidney diseases is still unknown. More specifically, it is not known whether MSCs halt fibrosis. The purpose of this work was to investigate the role of MSCs in fibrogenesis using a model of chronic renal failure. MSCs were obtained from the tibias and femurs of male Wistar-EPM rats. Female Wistar rats were subjected to the remnant model, and 2|x|10(5) MSCs were intravenously administrated to each rat every other week for 8 weeks or only once and followed for 12 weeks. SRY gene expression was observed in female rats treated with male MSCs, and immune localization of CD73(+)CD90(+) cells at 8 weeks was also assessed. Serum and urine analyses showed an amelioration of functional parameters in MSC-treated animals at 8 weeks, but not at 12 weeks. Masson's trichrome and Sirius red staining demonstrated reduced levels of fibrosis in MSC-treated animals. These results were corroborated by reduced vimentin, type I collagen, transforming growth factor beta, fibroblast specific protein 1 (FSP-1), monocyte chemoattractant protein 1, and Smad3 mRNA expression and alpha smooth muscle actin and FSP-1 protein expression. Renal interleukin (IL)-6 and tumor necrosis factor alpha mRNA expression levels were significantly decreased after MSC treatment, whereas IL-4 and IL-10 expression levels were increased. All serum cytokine expression levels were decreased in MSC-treated animals. Taken together, these results suggested that MSC therapy can indeed modulate the inflammatory response that follows the initial phase of a chronic renal injury. The immunosuppressive and remodeling properties of MSCs may be involved in the decreased fibrosis in the kidney.

Effects of creatine supplementation on renal function: a randomized, double-blind, placebo-controlled clinical trial

Creatine (CR) supplementation is commonly used by athletes. However, its effects on renal function remain controversial. The aim of this study was to evaluate the effects of creatine supplementation on renal function in healthy sedentary males (18-35 years old) submitted to exercise training. A randomized, double-blind, placebo-controlled trial was performed. Subjects (n = 18) were randomly allocated to receive treatment with either creatine (CR) ( approximately 10 g day(-1) over 3 months) or placebo (PL) (dextrose). All subjects undertook moderate intensity aerobic training, in three 40-min sessions per week, during 3 months. Serum creatinine, serum and urinary sodium and potassium were determined at baseline and at the end of the study. Cystatin C was assessed prior to training (PRE), after 4 (POST 4) and 12 weeks (POST 12). Cystatin C levels (mg L(-1)) (PRE CR: 0.82 +/- 0.09; PL: 0.88 +/- 0.07 vs. POST 12 CR: 0.71 +/- 0.06; PL: 0.75 +/- 0.09, P = 0.0001) were decreased over time, suggesting an increase in glomerular filtration rate. Serum creatinine decreased with training in PL but was unchanged with training in CR. No significant differences were observed within or between groups in other parameters investigated. The decrease in cystatin C indicates that high-dose creatine supplementation over 3 months does not provoke any renal dysfunction in healthy males undergoing aerobic training. In addition, the results suggest that moderate aerobic training per se may improve renal function.

Kleine-Levin syndrome. Clinical course, polysomnography and multiple sleep latency test. Case report

A case of Kleine-Levin syndrome, with chronic severe periodic hypersomnia is described in a 17-year-old female. The first episode started when she was 15 years old. The episodes were characterized by periodic hypersomnia accompanied by hyperphagia, lasting 5 days, and repeating at 28 to 60 day intervals. The severity of hypersomnia prevented her from attending school activities. Outside the hypersomnia periods, she was asymptomatic. EEG, brain computerized tomography and brain nuclear magnetic resonance were normal; all-night polysomnography, Multiple Sleep Latency Test (MSLT) and Epworth Sleepiness Scale (ESS) were within normal limits. During the period of hypersomnolence, polysomnography showed short sleep latency and short REM latency. MSLT mean sleep latency was 1.8 min; and REM period was present in one subtest; the ESS was markedly elevated.

Comparisons of models of cortical necrosis with segmental infarction

Sodium and water excretion were studied by standard clearance techniques in three experimental models where renal mass was reduced by superficial cortical necrosis (CN) or ischemic segmental infarction (SI). During hydropenia either CN or SI were able to conserve and regulate sodium to a very similar degree. After expansion of extracellular volume, CN reabsorbed less sodium and water than SI. In free-water clearance (CH2O) experiments, the 'apparent distal' sodium delivery was higher in CN than in SI, suggesting a decreased sodium and water reabsorption in the proximal tubules of juxtamedullary nephrons (JM). Both kidneys had similar CH2O when factored for inulin clearance but when CH2O was corrected for 'apparent distal' sodium delivery it was lower in CN than in SI, demonstrating an incapacity of JM to dilute urine. CN also showed less capacity to reabsorb free water than SI. Thus, the use of CN and SI within the same animal was useful to study functional differences between superficial and juxtamedullary nephrons. The present study also suggests that the kidney with superficial CN was unable to perform maximal urine dilution and concentration.

Renal concentrating defect in protein malnutrition: the role of the thick ascending limb of Henle and inner medullary collecting duct

The present study was carried out to examine the effect of chronic dietary protein restriction on renal water handling in the rat. During hypotonic saline infusion, the malnourished rats showed a lower free-water clearance, corrected by inulin clearance (7.2 +/- 0.4%), than normal rats (13.6 +/- 2.5%, p less than 0.051), although the fractional distal delivery of sodium did not differ from normal. Throughout hypertonic saline diuresis the free-water reabsorption (TcCH20) corrected by inulin clearance was lower in malnourished rats (6.62 +/- 0.64%) than in control animals (9.25 +/- 0.62, p less than 0.05). Moreover, when TcH20 was referred to the osmolar clearance, malnourished animals showed lower values than normal. These results suggest a defect in NaCl transport in the thick ascending limb of Henle. In vitro measurements of diffusional water permeability (PDW) in the inner medullary collecting duct (IMCD) obtained from malnourished rats showed an increase from 40.0 +/- 5.4 x 10(5) cm/s to 71.3 +/- 5.4 x 10(5) cm/s by adding maximum effective concentration (50 microU/ml) of arginine vasopressin (VP) to the bath. These values were not different from the PDW observed in the IMCD of normal rats. In another series of microperfusion experiments, the hydraulic conductivity in IMCD of malnourished rats measured also in the presence of maximum effective concentration of VP was 29.7 +/- 3.4 x 10(-6) cm/atm/s, a mean value not significantly different from that observed in the IMCD of normal rats (35.2 +/- 4.3 x 10(-6) cm/atm/s).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of protein restriction on the severity and recovery from ischemic renal failure

The effects of chronic dietary protein restriction on ischemic renal failure were evaluated in rats subjected to 90 min of bilateral renal clamping. The rats were kept on either 20% casein (regular) diet or casein-free (protein-free) diet 10 days before and 21 days after renal injury. Rats on regular protein diet showed higher levels of BUN and serum creatinine and had a lower inulin clearance (microliter/min/100 g BW) than animals on protein-free diet (289 +/- 34 vs 582 +/- 103, p less than 0.05) 2 days after ischemia. However, the inulin clearance measured 21 days following ischemia was significantly higher in rats on regular diet (1468 +/- 181) than those maintained on protein-free diet after ischemia (560 +/- 167). When unilateral 90 min ischemia was performed in rats on regular diet, the postischemic kidneys showed an incomplete recovery of the inulin clearance (226 +/- 35) compared to the contralateral kidney (900 +/- 116), 21 days after ischemia; whereas in rats on a protein-free diet the inulin clearance averaged 106 +/- 17 in the postischemic kidney and 345 +/- 41 in the right kidney. When left renal ischemia and contralateral nephrectomy were performed, the inulin clearance was 1149 +/- 74 in rats on regular diet and 534 +/- 60 in rats on protein-free diet, 21 days following renal insult. These results suggest that protein restriction can play a protective role against renal ischemia in an initial phase, but it limits the late recovery from ischemia. The presence of a normal contralateral kidney inhibits the functional recovery of the postischemic kidney and a contralateral nephrectomy produces a compensatory functional hypertrophy of the postischemic kidney, even in rats on a protein-free diet.

Renal concentration defect induced by cisplatin. The role of thick ascending limb and papillary collecting duct

The effects of cisplatin (5 mg/kg BW given intraperitoneally) on renal concentration mechanism were evaluated initially by clearance studies in rats 5-7 days after cisplatin administration and compared to normal rats. During hypotonic saline infusion, cisplatin rats showed a lower inulin clearance (0.56 +/- 0.07 vs. 1.12 +/- 0.09 ml/min/100 g BW, p less than 0.01), a higher fractional distal delivery (CNa + CH2O/Cin) (36.3 +/- 4.4 vs. 22.8 +/- 4.5%, p less than 0.05), and lower CH2O/CNa + CH2O (33.6 +/- 5.8 vs. 56.5 +/- 5.0%, p less than 0.01). During hypertonic saline infusion the TcH2O/Cosm was lower in cisplatin (18.3 +/- 1.1%) than in normal rats (33.4 +/- 3.5%, p less than 0.01). These results suggest a defect in NaCl transport in the thick ascending limb of Henle and proximal tubule. In order to characterize these tubular defects, we measured Na-K-ATPase activity (microM Pi/mg protein/h). In the renal cortex of cisplatin rats the ATPase activity was lower (18.1 +/- 3.2) than in normal rats (33.4 +/- 6.4, p less than 0.05), also in the inner strip of the outer medulla of cisplatin rats Na-K-ATPase was reduced (26.0 +/- 5.7) when compared with normal rats (67.3 +/- 9.2, p less than 0.01), presumably representing a decrease in enzyme activity in the thick ascending limb.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of potassium depletion on ischemic renal failure

The present study was carried out to examine the effect of potassium depletion in rat kidneys subjected to a temporary ischemic event produced by clamping of left renal artery. The postischemic kidneys of rats on a normal diet with adequate potassium intake showed an increase in H2O, Na and K excretion, with no change in inulin clearance whereas significant differences were found in potassium-deprived rats. Potassium depletion was brought about by dietary K deprivation for 10 days. K-depleted rats (serum K = 2.5 +/- 0.1 mEq/l) had a decrease in inulin clearance of the postischemic kidney from 1.01 +/- 0.10 to 0.43 +/- 0.05 ml/min (p less than 0.01), and a greater increase in fractional excretion of H2O, Na and K when compared to normal rats. The postischemic kidney from both normal and hypokalemic rats showed a decrease in Na-K-ATPase of the inner stripe of the outer medulla. These data indicate that short-term ischemia produces polyuria, increases natriuresis and kaliuresis, associated, at least in part, with a decrease in Na-K-ATPase in the inner stripe of the outer medulla (probably the thick ascending limb of Henle) and that K depletion potentiates ischemic renal failure.