Early morphological and neurochemical changes of the bed nucleus of stria terminalis (BNST) in gestational protein-restricted male offspring

BACKGROUND

The bed nucleus of the stria terminalis (BNST) is a structure with a peculiar neurochemical composition involved in modulating anxietylike behavior and fear.

AIM

The present study investigated the effects on the BNST neurochemical composition and neuronal structure in critical moments of the postnatal period in gestational protein-restricted male rats' offspring.

METHODS

Dams were maintained during the pregnancy on isocaloric rodent laboratory chow with standard protein content [NP, 17%] or low protein content [LP, 6%]. BNST from male NP and age-matched LP offspring was studied using the isotropic fractionator method, Neuronal 3D reconstruction, dendritic-tree analysis, blotting analysis, and high-performance liquid chromatography.

RESULTS

Serum corticosterone levels were higher in male LP offspring than NP rats in 14-day-old offspring, without any difference in 7-day-old progeny. The BNST total cell number and anterodorsal BNST division volume in LP progeny were significantly reduced on the 14th postnatal day compared with NP offspring. The BNST HPLC analysis from 7 days-old LP revealed increased norepinephrine levels compared to NP progeny. The BNST blot analysis from 7-day-old LP revealed reduced levels of GR and BDNF associated with enhanced CRF1 expression compared to NP offspring. 14-day-old LP offspring showed reduced expression of MR and 5HT1A associated with decreased DOPAC and DOPA turnover levels relative to NP rats. In Conclusion, the BNST cellular and neurochemical changes may represent adaptation during development in response to elevated fetal exposure to maternal corticosteroid levels. In this way, gestational malnutrition alters the BNST content and structure and contributes to already-known behavioral changes.

Impact of maternal protein restriction on Hypoxia-Inducible Factor (HIF) expression in male fetal kidney development

BACKGROUND

Kidney developmental studies have demonstrated molecular pathway changes that may be related to decreased nephron numbers in the male 17 gestational days (17GD) low protein (LP) intake offspring compared to normal protein intake (NP) progeny. Here, we evaluated the HIF-1 and components of its pathway in the kidneys of 17-GD LP offspring to elucidate the molecular modulations during nephrogenesis.

METHODS

Pregnant Wistar rats were allocated into two groups: NP (regular protein diet-17%) or LP (Low protein diet-6%). Taking into account miRNA transcriptome sequencing previous study (miRNA-Seq) in 17GD male offspring kidneys investigated predicted target genes and proteins related to the HIF-1 pathway by RT-qPCR and immunohistochemistry.

RESULTS

In the present study, in male 17-GD LP offspring, an increased elF4, HSP90, p53, p300, NFκβ, and AT2 gene encoding compared to the NP progeny. Higher labeling of HIF-1α CAP cells in 17-DG LP offspring was associated with reduced elF4 and phosphorylated elF4 immunoreactivity in LP progeny CAP cells. In 17DG LP, the NFκβ and HSP90 immunoreactivity was enhanced, particularly in the CAP area.

DISCUSSION AND CONCLUSION

The current study supported that the programmed reduced nephron number in the 17-DG LP offspring may be related to changes in the HIF-1α signaling pathway. Factors that facilitate the transposition of HIF-1α to progenitor renal cell nuclei, such as increased NOS, Ep300, and HSP90 expression, may have a crucial role in this regulatory system. Also, HIF-1α changes could be associated with reduced transcription of elF-4 and its respective signaling path.

Transcriptome and morphological analysis on the heart in gestational protein-restricted aging male rat offspring

Background: Adverse factors that influence embryo/fetal development are correlated with increased risk of cardiovascular disease (CVD), type-2 diabetes, arterial hypertension, obesity, insulin resistance, impaired kidney development, psychiatric disorders, and enhanced susceptibility to oxidative stress and inflammatory processes in adulthood. Human and experimental studies have demonstrated a reciprocal relationship between birthweight and cardiovascular diseases, implying intrauterine adverse events in the onset of these abnormalities. In this way, it is plausible that confirmed functional and morphological heart changes caused by gestational protein restriction could be related to epigenetic effects anticipating cardiovascular disorders and reducing the survival time of these animals.

Methods: Wistar rats were divided into two groups according to the protein diet content offered during the pregnancy: a normal protein diet (NP, 17%) or a Low-protein diet (LP, 6%). The arterial pressure was measured, and the cardiac mass, cardiomyocytes area, gene expression, collagen content, and immunostaining of proteins were performed in the cardiac tissue of male 62-weeks old NP compared to LP offspring.

Results: In the current study, we showed a low birthweight followed by catch-up growth phenomena associated with high blood pressure development, increased heart collagen content, and cardiomyocyte area in 62-week-old LP offspring. mRNA sequencing analysis identified changes in the expression level of 137 genes, considering genes with a p-value < 0.05. No gene was. Significantly changed according to the adj-p-value. After gene-to-gene biological evaluation and relevance, the study demonstrated significant differences in genes linked to inflammatory activity, oxidative stress, apoptosis process, autophagy, hypertrophy, and fibrosis pathways resulting in heart function disorders.

Conclusion: The present study suggests that gestational protein restriction leads to early cardiac diseases in the LP progeny. It is hypothesized that heart dysfunction is associated with fibrosis, myocyte hypertrophy, and multiple abnormal gene expression. Considering the above findings, it may suppose a close link between maternal protein restriction, specific gene expression, and progressive heart failure.

Severe Gestational Low-Protein Intake Impacts Hippocampal Cellularity, Tau, and Amyloid-β Levels, and Memory Performance in Male Adult Offspring: An Alzheimer-Simile Disease Model?

Background:

Maternal undernutrition has been associated with psychiatric and neurological disorders characterized by learning and memory impairment.

Objective:

Considering the lack of evidence, we aimed to analyze the effects of gestational protein restriction on learning and memory function associated with hippocampal cell numbers and neurodegenerative protein content later in life.

Methods:

Experiments were conducted in gestational low- (LP, 6% casein) or regular-protein (NP, 17% casein) diet intake offspring. Behavioral tests, isolated hippocampal isotropic fractionator cell studies, immunoblotting, and survival lifetime were observed.

Results:

The birthweight of LP males is significantly reduced relative to NP male progeny, and hippocampal mass increased in 88-week-old LP compared to age-matched NP offspring. The results showed an increased proximity measure in 87-week-old LP compared to NP offspring. Also, LP rats exhibited anxiety-like behaviors compared to NP rats at 48 and 86-wk of life. The estimated neuron number was unaltered in LP rats; however, non-neuron cell numbers increased compared to NP progeny. Here, we showed unprecedented hippocampal deposition of brain-derived neurotrophic factor, amyloid-β peptide (Aβ), and tau protein in 88-week-old LP relative to age-matched NP offspring.

Conclusion:

To date, no predicted studies showed changes in hippocampal morphological structure in maternal protein-restricted elderly offspring. The current data suggest that gestational protein restriction may accelerate hippocampal function loss, impacting learning/memory performance, and supposedly developing diseases similar to Alzheimer’s disease (AD) in elderly offspring. Thus, we propose that maternal protein restriction could be an elegant and novel method for constructing an AD-like model in adult male offspring.

Gestational and Breastfeeding Low-Protein Intake on Blood Pressure, Kidney Structure, and Renal Function in Male Rat Offspring in Adulthood

Background: Our previous studies demonstrated that maternal protein-restricted (low-protein, LP) 16-week-old offspring had pronounced nephron number reduction and arterial hypertension associated with an unchanged glomerular filtration rate (GFR). An enhanced gomerular area may be related to increased glomerular filtration and overflow, which accounts for glomerular filtration barrier breakdown and early glomerulosclerosis. The effect of protein restriction during gestational and breastfeeding periods is unknown. Method: The functional e-structural kidney evaluation was obtained using lithium and creatinine clearance, kidney morphometry, immunoblotting, and immunostaining analysis in 16 and 24-week-old LP offspring compared to age-matched NP progeny. Results: Low protein rats' progeny had significantly reduced birth weight, without previous catch-up growth phenomena, in parallel with a decreased adiposity index. Transforming growth factor-beta 1 (TGF-β1) glomerular expression was significantly enhanced in the LP group. Also, the LP offspring had a 38% lower nephron number and an increased glomerular volume. They also presented with a higher cardiac index and arterial blood pressure compared with age-matched NP offspring. The LP rats exhibited augmented Na+/K+-ATPase in the proximal segments, and NOS1 immunoreactivity in whole renal tissue was associated with sodium retention in the proximal nephron segments. We also found significantly enhanced collagen content associated with increased TGFβ1 and ZEB1/2 renal immunoreactivity in LP offspring compared with NP offspring. Increased hypertrophy markers in LP podocytes were associated with an amplified IL-6/STAT3 pathway activity. Conclusion: To our knowledge, these are the first data demonstrating renal functional and structural changes in protein restriction during gestation and lactation model of fetal programming. The fetal-programmed adult offspring showed pronounced structural glomerular disorders with an accentuated and advanced fibrosis stage, without a change in the GFR. These findings suggest that the glomerular enhanced TGF-β1 action may induce ZEB1/2 expression that may cause glomeruli epithelial-to-mesenchymal transition. Besides, decreased nephron number in the LP offspring with preserved glomerular function may be related to protective or even attenuate the activated IL-6/STAT3 pathway.

Estimation of the kidney metabolic heat generation rate

Thermogenesis results from the cellular metabolism and has a fundamental role for body thermoregulation in endothermic species. The motivation for this work is the analysis of the kidneys' contribution for thermoregulation. An inverse problem is solved for the estimation of the heat generation rate that results from the metabolic activities in the kidney, by using transient temperature measurements of the urine. The Markov chain Monte Carlo (MCMC) method is applied for the solution of the inverse problem, which presents inherent difficulties associated with low sensitivity of the parameters of main interest that represent the transient heat source term and strong correlation of the remaining model parameters. Such difficulties are dealt with in this work by using a version of the Metropolis-Hastings algorithm that samples the parameters in blocks. Simulated temperature measurements are used for the inverse problem solution, and the convergence of the Markov chains is verified with two different techniques.

miRNAs, target genes expression and morphological analysis on the heart in gestational protein-restricted offspring

Gestational protein restriction was associated with low birth weight, hypertension and higher prevalence of cardiac disorders in adults. Several mechanisms, including epigenetics, could be related with the cardiovascular phenotype on protein-restricted offspring. Thus, we investigated the morphological cardiac effects of gestational protein restriction and left ventricle miRNAs and target genes expression pattern in both 12-day and 16-week old gestational protein-restricted male offspring. Pregnant Wistar rats were allocated into two groups, according to protein supply during pregnancy: NP (normal protein diet- 17%) or LP (low protein diet-6%). Dams on the gestational protein-restricted diet had lower body weight gain and higher food intake. Gestational protein-restricted offspring had low birth weight, followed by rapidly body weight recovery, hypertension, and increased myocytes cross-sectional area and collagen fraction at 16-week old age. At 12-days old, miR-184, miR-192, miR-376c, miR-380-3p, miR-380-5p, miR-451, and miR-582-3p had increased expression, and miR-547 and miR-743a had decreased expression in the gestational protein-restricted left ventricle. At 16-week old, let-7b, miR-125a-3p, miR-142-3p, miR-182 and miR-188-5p had increased expression and let-7g, miR-107, miR-127, miR-181a, miR-181c, miR-184, miR-324-5p, miR-383, miR-423-5p and miR-484 had decreased expression in gestational protein-restricted left ventricle. Target predicted gene expression analysis showed higher expression of Dnmt3a, Oxct1, Rictor and Trps1 and lower expression of Bbs1 and Calml3 in 12-day old protein-restricted offspring. 16-week old protein-restricted offspring had higher expression of Adrbk1, Bbs1, Dnmt3a, Gpr22, Inppl1, and Oxct1 genes. In conclusion, gestational protein restriction was related to offspring low birth weight, increased systolic blood pressure and morphological heart alterations that could be related to early heart miRNA expression changes that perpetuate into adulthood and which are associated with the regulation of essential genes involved in cardiovascular development, heart morphology, function, and metabolism.

Effect of intracerebroventricular epinephrine microinjection on blood pressure and urinary sodium handling in gestational protein-restricted male adult rat offspring

In this study, we hypothesized that blunting of the natriuresis response to intracerebroventricularly (ICV) microinjected adrenergic agonists is involved in the development of hypertension in maternal low-protein intake (LP) offspring. A stainless steel cannula was stereotaxically implanted into the right lateral ventricle (LV), then we evaluated the ICV administration of adrenergic agonists at increasing concentrations, and of α1 and α2-adrenoceptor antagonists on blood pressure and urinary sodium handling in LP offspring relative to an age-matched normal-protein intake (NP) group. We confirmed that epinephrine (Epi) microinjected into the LV of conscious NP rats leads to enhanced natriuresis followed by a reduction in arterial pressure. This response is associated with increased proximal and post-proximal sodium excretion accompanied by an unchanged glomerular filtration rate. The current study showed, in both NP and LP offspring, that the natriuretic effect of Epi injection into the LV was abolished by prior local microinjection of an α1-adrenoceptor antagonist (prazosin). Conversely, LV α2-adrenoceptor antagonist (yohimbine) administration potentiated the action of Epi. The LV yohimbine pretreatment normalized urinary sodium excretion and reduced the blood pressure in LP compared with age-matched NP offspring. These are, as far as we are aware, the first results showing the role of central adrenergic receptors’ interaction on hypertension pathogenesis in maternal LP fetal-programming offspring. This study also provides good evidence for the existence of central nervous system adrenergic mechanisms consisting of α1 and α2-adrenoceptors, which work reciprocally on the control of renal sodium excretion and blood pressure. Although the precise mechanism of the different natriuretic response of NP and LP rats is still uncertain, these results lead us to speculate that inappropriate neural adrenergic pathways might have significant effects on tubule sodium transport, resulting in the inability of the kidneys to control hydrosaline balance and, consequently, an increase in blood pressure.

Summary: We evaluated the effect of intracerebroventricular microinjections of adrenergic agonists at increasing concentrations, and μ1 and μ2-adrenergic receptors antagonists on blood pressure and urinary sodium in hypertensive low- and normal-protein rat offdpring.

Association between prehypertension, metabolic and inflammatory markers, decreased adiponectin and enhanced insulinemia in obese subjects

Background

Obesity is associated with development of the cardiorenal metabolic syndrome, which is a constellation of risk factors, such as insulin resistance, inflammatory response, dyslipidemia, and high blood pressure that predispose affected individuals to well-characterized medical conditions such as diabetes, cardiovascular and kidney chronic disease. The study was designed to establish relationship between metabolic and inflammatory disorder, renal sodium retention and enhanced blood pressure in a group of obese subjects compared with age-matched, lean volunteers.

Methods

The study was performed after 14 h overnight fast after and before OGTT in 13 lean (BMI 22.92 ± 2.03 kg/m²) and, 27 obese (BMI 36.15 ± 3.84 kg/m²) volunteers. Assessment of HOMA-IR and QUICKI index were calculated and circulating concentrations of TNF-α, IL-6 and C-reactive protein, measured by immunoassay.

Results

The study shows that a hyperinsulinemic (HI: 10.85 ± 4.09 μg/ml) subgroup of well-characterized metabolic syndrome bearers-obese subjects show higher glycemic and elevated blood pressure levels when compared to lean and normoinsulinemic (NI: 5.51 ± 1.18 μg/ml, P < 0.027) subjects. Here, the combination of hyperinsulinemia, higher HOMA-IR (HI: 2.19 ± 0.70 (n = 12) vs. LS: 0.83 ± 0.23 (n = 12) and NI: 0.98 ± 0.22 (n = 15), P < 0.0001) associated with lower QUICKI in HI obese when compared with LS and NI volunteers (P < 0.0001), suggests the occurrence of insulin resistance and a defect in insulin-stimulated peripheral action. Otherwise, the adiponectin measured in basal period was significantly enhanced in NI subjects when compared to HI groups (P < 0.04). The report also showed a similar insulin-mediated reduction of post-proximal urinary sodium excretion in lean (LS: 9.41 ± 0.68% vs. 6.38 ± 0.92%, P = 0.086), and normoinsulinemic (NI: 8.41 ± 0.72% vs. 5.66 ± 0.53%, P = 0.0025) and hyperinsulinemic obese subjects (HI: 8.82 ± 0.98% vs. 6.32 ± 0.67%, P = 0.0264), after oral glucose load, despite elevated insulinemic levels in hyperinsulinemic obeses.

Conclusion

In conclusion, this study highlights the importance of adiponectin levels and dysfunctional inflammatory modulation associated with hyperinsulinemia and peripheral insulin resistance, high blood pressure, and renal dysfunction in a particular subgroup of obeses.

Early detection of metabolic and energy disorders by thermal time series stochastic complexity analysis

Maintenance of thermal homeostasis in rats fed a high-fat diet (HFD) is associated with changes in their thermal balance. The thermodynamic relationship between heat dissipation and energy storage is altered by the ingestion of high-energy diet content. Observation of thermal registers of core temperature behavior, in humans and rodents, permits identification of some characteristics of time series, such as autoreference and stationarity that fit adequately to a stochastic analysis. To identify this change, we used, for the first time, a stochastic autoregressive model, the concepts of which match those associated with physiological systems involved and applied in male HFD rats compared with their appropriate standard food intake age-matched male controls (n=7 per group). By analyzing a recorded temperature time series, we were able to identify when thermal homeostasis would be affected by a new diet. The autoregressive time series model (AR model) was used to predict the occurrence of thermal homeostasis, and this model proved to be very effective in distinguishing such a physiological disorder. Thus, we infer from the results of our study that maximum entropy distribution as a means for stochastic characterization of temperature time series registers may be established as an important and early tool to aid in the diagnosis and prevention of metabolic diseases due to their ability to detect small variations in thermal profile.

Impact of taurine supplementation on blood pressure in gestational protein-restricted offspring: Effect on the medial solitary tract nucleus cell numbers, angiotensin receptors, and renal sodium handling

OBJECTIVE

The current study considers changes of the postnatal brainstem cell number and angiotensin receptors by maternal protein restriction (LP) and LP taurine supplementation (LPT), and its impact on arterial hypertension development in adult life.

METHODS AND RESULTS

The brain tissue studies were performed by immunoblotting, immunohistochemistry, and isotropic fractionator analysis. The current study shows that elevated blood pressure associated with decreased fractional urinary sodium excretion (FENa) in adult LP offspring was reverted by diet taurine supplementation. Also, that 12-day-old LP pups present a reduction of 21% of brainstem neuron counts, and, immunohistochemistry demonstrates a decreased expression of type 1 angiotensin II receptors (AT1R) in the entire medial solitary tract nuclei (nTS) of 16-week-old LP rats compared to age-matched NP and LPT offspring. Conversely, the immunostained type 2 AngII (AT2R) receptors in 16-week-old LP nTS were unchanged.

CONCLUSION

The present investigation shows a decreased FENa that occurs despite unchanged creatinine clearance. It is plausible to hypothesize an association of decreased postnatal nTS cell number, AT1R/AT2R ratio and FENa with the higher blood pressure levels found in taurine-deficient progeny (LP) compared with age-matched NP and LPT offspring.

Gestational protein restriction induces CA3 dendritic atrophy in dorsal hippocampal neurons but does not alter learning and memory performance in adult offspring

Studies have demonstrated that nutrient deficiency during pregnancy or in early postnatal life results in structural abnormalities in the offspring hippocampus and in cognitive impairment. In an attempt to analyze whether gestational protein restriction might induce learning and memory impairments associated with structural changes in the hippocampus, we carried out a detailed morphometric analysis of the hippocampus of male adult rats together with the behavioral characterization of these animals in the Morris water maze (MWM). Our results demonstrate that gestational protein restriction leads to a decrease in total basal dendritic length and in the number of intersections of CA3 pyramidal neurons whereas the cytoarchitecture of CA1 and dentate gyrus remained unchanged. Despite presenting significant structural rearrangements, we did not observe impairments in the MWM test. Considering the clear dissociation between the behavioral profile and the hippocampus neuronal changes, the functional significance of dendritic remodeling in fetal processing remains undisclosed.

Kidney safety during surgical pneumoperitoneum: an experimental study in rats

BACKGROUND

Elevations of intraabdominal pressure during laparoscopic procedures may lead to oliguria or anuria in mammals. Despite this, previous research has not been able to confirm an associated kidney injury. This study aimed to investigate the occurrence of an early kidney lesion secondary to surgical pneumoperitoneum in a rat model using the expression of neutrophil gelatinase-associated lipocalin (N-GAL) as a biomarker for early kidney injury.

METHODS

In this study, 20 male Sprague-Dawley rats under general anesthesia and mechanically ventilated were allocated to one of five experimental time-dependent groups: group 1 (1-h control), group 2 (1-h pneumoperitoneum), group 3 (2-h control), group 4 (2-h pneumoperitoneum), and group 5 (positive kidney injury group induced by intravenous administration of cisplatin 7.5 mg/kg). To evaluate the renal expression of N-GAL 24 h after the procedure, all the rats underwent a 2-h urine output evaluation as well as laparotomy and bilateral nephrectomy performed sequentially to investigate the presence of renal injury using immunofluorescence qualification and western blotting.

RESULTS

Urine output was reduced and N-GAL expression was increased in the animals from the cisplatin group. The animals undergoing 1- or 2-h pneumoperitoneum displayed urine output and N-GAL expression similar to that of the animals from the matching control groups.

CONCLUSIONS

Under the experimental conditions of this study, the animals with normal preoperative renal function did not show any type of acute kidney injury associated with the presence of a stabilized surgical pneumoperitoneum.

Impaired dipsogenic and renal response to repetitive intracerebroventricular angiotensin II (AngII) injections in rats

The role of the central nervous system (CNS) in the control of blood pressure and hydrosaline homeostasis has been demonstrated by several studies. While circulating angiotensin II (AngII) tends to retain sodium by a direct renal action as well as through aldosterone release, stimulation of brain AngII receptors has been reported to induce natriuresis. Repetitive intracerebroventricular AngII injection was recently demonstrated to be capable of leading to desensitisation of the dipsogenic effect of AngII stimuli. The aim of the current study was to investigate a possible central desensitisation to AngII stimuli by observing the effects of a low-concentration solution of AngII on the dipsogenic and natriuretic mechanisms in conscious rats, compared with appropriate age-matched 0.15 M NaCl-injected subjects, as evaluated by lithium clearance. The present report confirmed earlier reports on the potent natriuretic and dipsogenic effects of central AngII receptor stimulation. Natriuresis is mediated by a decrease in sodium reabsorption in the proximal and post-proximal tubule segments of the nephron. The current findings lend further support to the idea that AngII, in the CNS, is instrumental in the regulation of body fluid homeostasis. The magnitude of the dipsogenic and renal response to AngII was significantly decreased by repetitive stimulus.

Hypothalamic SOCS-3 expression and the effect of intracerebroventricular angiotensin II injection on water intake and renal sodium handling in SHR

In rats, the acute central dipsogenic and natriuretic action of angiotensin II (AngII) seems to be independent of the hemodynamic effects of the peptide; however, in genetically hypertensive models, this relationship has not yet been investigated. It has been demonstrated that AngII induces the suppressor of cytokine signaling (SOCS-3) expression in the brain that, in turn, modulates further activation of the pathway, leading to desensitization to AngII stimuli with regard to its dipsogenic effect. This study investigates age-related Janus kinase (JAK-2) and SOCS-3 hypothalamic expression, by immunoblotting, and the involvement of SOCS-3 expression in urinary sodium handling and dipsogenic response in spontaneously hypertensive rats (SHR), compared with age-matched Wistar-Kyoto (WKy) rats. The intracerebroventricular (i.c.v.) application of AngII significantly enhanced the dipsogenic response, reduced C(Cr), and reciprocally promoted increased absolute and fractional rates of excretion of sodium in WKy rats. The central AngII-induced dipsogenic effect in WKy and SHR was significantly attenuated by prior i.c.v. administration of DUP753. In addition, the magnitude of the dipsogenic and renal response to AngII was significantly attenuated in age-matched SHR. Blocking of hypothalamic SOCS-3 expression by an antisense oligonucleotide resulted in partial reversal of the refractory nature of AngII in thirst responses in SHR. The altered centrally applied AngII response in SHR associated with increased hypothalamic JAK-2/SOCS-3 expression may suggest that abnormal regulation of the central angiotensin pathways may contribute to dysfunction of water-electrolyte homeostasis in SHR.

Maternal undernutrition and the offspring kidney: from fetal to adult life

Maternal dietary protein restriction during pregnancy is associated with low fetal birth weight and leads to renal morphological and physiological changes. Different mechanisms can contribute to this phenotype: exposure to fetal glucocorticoid, alterations in the components of the renin-angiotensin system, apoptosis, and DNA methylation. A low-protein diet during gestation decreases the activity of placental 11ß-hydroxysteroid dehydrogenase, exposing the fetus to glucocorticoids and resetting the hypothalamic-pituitary-adrenal axis in the offspring. The abnormal function/expression of type 1 (AT1(R)) or type 2 (AT2(R)) AngII receptors during any period of life may be the consequence or cause of renal adaptation. AT1(R) is up-regulated, compared with control, on the first day after birth of offspring born to low-protein diet mothers, but this protein appears to be down-regulated by 12 days of age and thereafter. In these offspring, AT2(R) expression differs from control at 1 day of age, but is also down-regulated thereafter, with low nephron numbers at all ages: from the fetal period, at the end of nephron formation, and during adulthood. However, during adulthood, the glomerular filtration rate is not altered, due to glomerulus and podocyte hypertrophy. Kidney tubule transporters are regulated by physiological mechanisms; Na(+)/K(+)-ATPase is inhibited by AngII and, in this model, the down-regulated AngII receptors fail to inhibit Na(+)/K(+)-ATPase, leading to increased Na(+) reabsorption, contributing to the hypertensive status. We also considered the modulation of pro-apoptotic and anti-apoptotic factors during nephrogenesis, since organogenesis depends upon a tight balance between proliferation, differentiation and cell death.

Consequences of cerebroventricular insulin injection on renal sodium handling in rats: effect of inhibition of central nitric oxide synthase

In the present study, we investigated the effects of acute intracerebroventricular (icv) insulin administration on central mechanisms regulating urinary sodium excretion in simultaneously centrally NG-nitro-L-arginine methylester (L-NAME)-injected unanesthetized rats. Male Wistar-Hannover rats were randomly assigned to one of five groups: a) icv 0.15 M NaCl-injected rats (control, N = 10), b) icv dose-response (1.26, 12.6 and 126 ng/3 microL) insulin-injected rats (N = 10), c) rats icv injected with 60 microg L-NAME in combination with NaCl (N = 10) or d) with insulin (N = 10), and e) subcutaneously insulin-injected rats (N = 5). Centrally administered insulin produced an increase in urinary output of sodium (NaCl: 855.6 +/- 85.1 Delta%/min; 126 ng insulin: 2055 +/- 310.6 Delta%/min; P = 0.005) and potassium (NaCl: 460.4 +/- 100 Delta%/min; 126 ng insulin: 669.2 +/- 60.8 Delta%/min; P = 0.025). The urinary sodium excretion response to icv 126 ng insulin microinjection was significantly attenuated by combined administration of L-NAME (126 ng insulin: 1935 +/- 258.3 Delta%/min; L-NAME + 126 ng insulin: 582.3 +/- 69.6 Delta%/min; P = 0.01). Insulin-induced natriuresis occurred by increasing post-proximal sodium excretion, despite an unchanged glomerular filtration rate. Although the rationale for decreased urinary sodium excretion induced by combined icv L-NAME and insulin administration is unknown, it is tempting to suggest that perhaps one of the efferent signals triggered by insulin in the CNS may be nitrergic in nature.

Effect of Nitric Oxide Synthase Inhibition and Saline Administration on Blood Pressure and Renal Sodium Handling During Experimental Sepsis in Rats

Much effort has been made in recent years to clarify metabolic and renal function changes in sepsis. A number of studies performed in different models of sepsis have been described. One such model that is frequently used is cecal ligation and puncture (CLP) in rats. This model resembles human sepsis in several important aspects, such as an early phase of hyperdynamic, hypermetabolic sepsis followed by a late hypodynamic, hypometabolic phase. The present study evaluated the blood pressure (n = 5) and renal function changes during development of CLP renal failure and to determine the effects of NOS inhibition (L-NAME) and 0.15 M NaCl administration on tail blood pressure and renal function in randomly assigned five groups (n = 10 each): (1) Sham-operated, (2) Sham-operated L-NAME-treated, (3) CLP rats, (4) CLP L-NAME-treated, and (5) CLP 0.15 M NaCl-treated rats. The basal tail blood pressure was not significantly different among the four groups. One week later, arterial pressure was significantly increased in sham-operated L-NAME-treated rats (159 +/- 12 mmHg) compare with the other groups (118 +/- 9.0 mmHg in nontreated rats, p < 0.05). Blood pressure shows a slightly and not significant decrease up to 12h in L-NAME and 0.15 M NaCl treated rats, which in turn was followed by a significant reduced arterial pressure 18h after CLP in both groups (L-NAME: 96.0 +/- 3.6 mmHg, p < 0.05) and NaCl: 82.3 +/- 2.4 mmHg, p < 0.05) compared to sham-operated groups. The glomerular filtration rate estimated by CCr decreases significantly in the CLP untreated group (p < 0.001) and did not significantly differ from the sham-operated and L-NAME-treated groups (p = 0.4) during the studies of renal tubule sodium handling. On the other hand, subcutaneous 0.15 M NaCl administration prevented CCr decreases in CLP rats (p = 0.25). CLP increased the FENa in the sham-operated from: 857.2 +/- 85.1 delta%min(-1) to CLP: 1197.8 +/- 119.0 delta%min(-1). The high FENa to CLP was blunted and significantly reduced by previous systemic treatment of animals with L-NAME from sham-operated+L-NAME: 1368.0 +/- 72.0 delta%min(-1) to CLP+L-NAME: 1148.0 +/- 60.4 delta%min(-1) (p < 0.01). The enhanced FENa in the CLP group were accompanied by a significant increase in proximal sodium reabsorption rejection. The salient findings of the present study suggest that a decrease in the blood pressure and creatinine clearance caused by CLP may benefit from L-NAM and fluid resuscitation during initial bacteremia (first 12 h) by promoting an additional increase of tubule sodium reabsorption in the post-proximal segments of nephrons, but these therapies could not prevent acute renal failure after established endotoxemia.

Actin cytoskeletal and functional studies of the proximal convoluted tubules after preservation

BACKGROUND

Proximal tubule cells have specialized apical membranes with microvilli that provide an extensive surface area for unidirectional transport of solute from lumen to blood. The major structural solute component is F-actin, which interacts with transmembrane proteins, including ion transport molecules related to normal absorptive and secretory functions. Our study was to evaluate F-actin and fluid absorption (Jv) in proximal tubules after exposure to preservation solutions.

METHODS

In vitro microperfusion technique and immunohistochemistry analysis.

RESULTS

1. Absorptions were similar in 1- and 24-hour-preserved tubules, as well as in fresh tubules. The exception was tubules for 24 hours in Euro-Collins solution, which did not show absorption, suggesting that it was affected. 2. Fluorescence intensity of actin tubules preserved for 1 hour in both solutions showed similar values to each other and to the control group; tubules preserved for 24 hours in both solutions were similar to each other, although statistically different than the control group and those preserved for 1 hour in Belzer (UW) solution.

CONCLUSION

There were differences among groups in the distribution of F-actin; Jv values were different for 24-hour preservation in each solution, whereas fluorescence intensity was similar in both 24-hour solutions. Thus, actin cytoskeleton was not responsible for it, because 24-hour preservation in UW showed Jv results comparable to the control group.

Effects of NH4Cl-induced systemic metabolic acidosis on kidney mitochondrial coupling and calcium transport in rats

BACKGROUND

We have previously shown that chronic metabolic acidosis, induced in rats by NH(4)Cl feeding, leads to nephron hypertrophy and to a decreased water-salt reabsorption by the kidneys. Since mitochondria are the main source of metabolic energy that drives ion transport in kidney tubules, we examined energy-linked functions (respiration, electrochemical membrane potential and coupling between respiration and ADP phosphorylation) in mitochondria isolated from rat kidney and liver at 48 h after metabolic acidosis induced by NH(4)Cl.

METHODS

Mitochondria isolated from the kidneys and liver of metabolic acidotic rats, induced by NH(4)Cl, was used to study of the oxygen consumption by Clark-type electrode, mitochondrial electrical transmembrane potential estimated by the safranine O method and the variations in free medium Ca(2+) concentrations examined by absorbance spectrum of Arsenazo III set at the 675-685 nm wavelength pair.

RESULTS

Whole kidney and liver mitochondria isolated from 48 h acidotic rats presented higher resting respiration, lower respiratory control and a lower ADP/O ratio than controls. These differences in mitochondrial coupling, between respiration and oxidative phosphorylation (ATP synthesis), were totally corrected when experiments were carried out in the presence of carboxyatractyloside, GDP and BSA, indicating that mitochondrial uncoupling proteins are more active in acidotic rat kidneys. Interestingly, determination of Ca(2+) transport demonstrated a faster rate of initial Ca(2+) uptake by acidotic kidney mitochondria, which resulted in a lower concentration of extra-mitochondrial Ca(2+) under steady-state conditions (Ca(2+) set point) when compared with control mitochondria. In contrast, there were no significant differences in the rates of Na(+) or ruthenium red induced Ca(2+) efflux.

CONCLUSIONS

We suggest that the mild uncoupling and higher Ca(2+) accumulation represents an adaptation of the mitochondria to cope with conditions of oxidative stress and high cytosolic Ca(2+), which are associated with a decreased efficiency of oxidative phosphorylation that may explain, at least in part, the striking natriuresis observed under chronic acidosis. Finally, there were no changes in Ca(2+) transport or coupling in liver mitochondria isolated from the acidotic rats.

Development of hypertension in a pyelonephritis-induced model: the effect of salt intake and inability of renal sodium handling

The role of the kidney in the control of blood pressure has been convincingly demonstrated by several studies. Recent evidence has suggested that subtle acquired tubulointerstitial injury may cause a defect in sodium excretion function, thus leading to salt-sensitive hypertension. There are no reports, however, examining the effect of experimental chronic pyelonephritis on renal sodium handling and arterial pressure. Thus, to examine the influence of salt intake and unilateral nephrectomy, unanesthetized, unrestrained rats were randomly assigned to one of two separate groups: sham-operated rats (CO) or chronic unilateral pyelonephritic rats (CP). After twenty one days, the pyelonephritic group was subdivided in two: one subgroup continued with water intake (CPw), while the other was changed to 0.9% NaCl intake (CPs), like the control group (COs). After seven days, all rats were submitted to unilateral nephrectomy of the left normal kidney. Data presented herein show that chronic pyelonephritis produced an increase in mean arterial pressure (CO: 121.4 +/- 1.0 mmHg to CP: 127.0 +/- 0.9 mmHg, p = 0.000) that was enhanced by saline ingestion (COs: 121.6 +/- 1.4 mmHg; CPw: 127.0 +/- 1.8 mmHg; CPs: 132.1 +/- 1.2 mmHg, p = 0.000) and further aggravated by unilateral nephrectomy (CO: 125.2 +/- 2.6 mmHg; CPw: 127.5 +/- 0.9 mmHg; CPs: 139.2 +/- 1.1 mmHg, p = 0.000). Unchanged blood pressure measurements (120.2 +/- 2.3 mmHg) were observed beyond 21 days in control rats maintained on water regimen when compared with saline-drinking groups. These changes in mean arterial pressure were observed despite an increased fractional sodium excretion in the CPs group compared to the other groups before uninephrectomy (COs: 0.125 +/- 0.025%; CPw: 0.045 +/- 0.013%; CPs: 0.292 +/- 0.046%; p = 0.000), as compared to CPw after uninephrectomy (COs: 0.249 +/- 0.077%; CPw: 0.062 +/- 0.011%; CPs: 0.363 +/- 0.195%, p = 0.019). In addition, it was shown that daily liquid intake was higher in CPs than in CPw but similar to COs, both before uninephrectomy (COs: 42.8 +/- 2.6 ml/d; CPw: 34.3 +/- 3.5 ml/d; CPs: 51.8 +/- 3.7 ml/d, p = 0.006) and after uninephrectomy (COs: 40.9 +/- 5.5 ml/d; CPw: 33.8 +/- 1.4 ml/d; CPs: 53.0 +/- 3.5 ml/d, p = 0.004). The current data suggest that chronic pyelonephritis promotes an inability of renal tubules to handle sodium excretion when exposed to sodium overload and aggravated by uninephrectomy, thus constituting a model for salt-sensitive hypertension.

Altered renal sodium handling in spontaneously hypertensive rats (SHR) after hypertonic saline intracerebroventricular injection: role of renal nerves

The mechanism by which blood pressure rises in the SHR strain remains to be elucidated. Also, there is a surprising lack of experimental data on the natriuretic mechanisms induced by intracerebroventricular (ICV) injection of hyperosmotic saline (HoS) in SHR. In normotensive animals ICV injection of HoS causes coordinated responses including natriuresis and inhibition of renal sympathetic nerve activity. In the present study, we hypothesized that presumable blunting of the sympathoinhibitory response to centrally injected HoS may contribute to a lack of suppression of efferent renal nerve outflow in SHR. To test this hypothesis, the present study evaluates the influence of renal denervation after central HoS injection at increasing concentration on urinary sodium handling in SHR compared with age-matched normotensive WKy rats. The study confirmed previous data showing pronounced natriuretic response to centrally HoS stimuli but also demonstrated that the creatinine clearance (C(Cr)) and fractional sodium excretion responses diminished as graded NaCl concentrations were increased in WKy rats but not in SHR. In SHR, increased FE(Na) obtained by central administration of 0.90 M NaCl was produced by increases in proximal (FEP(Na)) and post-proximal fractional urinary sodium rejection without changes in C(Cr), indicating a direct tubular effect. Renal denervation caused significant antinatriuresis by decreased C(Cr) and increased FEP(Na) reabsorption in WKy but not in SHR. This study suggests that natriuresis observed only after higher centrally HoS stimuli with a rightward shift of dose-response curve provides evidence of a down-regulation of target organ responsiveness of periventricular areas of genetic hypertensive rats.

Nuclear localization of SP, CGRP, and NK1R in a subpopulation of dorsal root ganglia subpopulation cells in rats

Signals generated by renal pelvic afferent nerves in response to stimulation are transmitted from peripheral processes of dorsal root ganglia neurons to their central terminals in the dorsal horn of the spinal cord to cause the release of neuropeptides, including SP and CGRP. All of the cellular activities of SP are considered to be mediated through interaction with NK(1)R located on the cell surface. We have investigated the colocalization and subcellular distribution of NK(1)R, SP, and CGRP in different subpopulations of neurons that innervate renal tissue. Our findings therefore provide the first evidence for the presence of NK(1)R, SP, and CGRP in the nuclei of DGR neural cells. The physiological significance of this localization remains unknown. One possibility is that pelvic sensory neurons may regulate their responses to different stimuli by modulating the ratio of CGRP and SP release and/or nuclear NK(1)R expression.

Hemodynamic parameters and neurogenic pulmonary edema following spinal cord injury: an experimental model

Neurogenic pulmonary edema is a serious and always life-threatening complication following several lesions of the central nervous system. We report an experiment with 58 Wistar-Hanover adult male rats. Two groups were formed: control (n=4) and experimental (n=54). The experimental group sustained acute midthoracic spinal cord injury by Fogarty’s balloon-compression technique containing 20µL of saline for 5, 15, 30 or 60 seconds. The rats were anesthetized by intraperitoneal (i.p.) sodium pentobarbital (s.p.) 60 mg/Kg. The quantitative neurological outcome was presented at 4, 24 and 48 hours from compression to characterize the injury graduation in different groups. Poor outcome occurred with 60 seconds of compression. Six animals died suddenly with pulmonary edema. Using the procedure to investigate the pulmonary edema during 60 seconds of compression, followed by decompression and time-course of 60 seconds, 20 rats were randomly asigned to one of the following groups: control (1, n=4, anesthetized by i.p. s.p., 60 mg/Kg but without compression) and experimental (2, n=7, anesthetized by i.p. xylazine 10 mg/Kg and ketamine 75 mg/Kg) and (3, n=9, anesthetized by i.p. s.p., 60 mg/Kg). The pulmonary index (100 x wet lung weight / body weight) was 0.395 ± 0.018 in control group, rose to 0.499 ± 0.060 in group 2, and was 0.639 ± 0.14 in group 3. Histologic examination of the spinal cord showed parenchymal ruptures and acute hemorrhage. Comparison of the pulmonary index with morphometric evaluation of edema fluid-filled alveoli by light microscopy showed that relevant intra-alveolar edema occurred only for index values above 0.55. The results suggest that the pulmonary edema induced by spinal compression is of neurogenic nature and that the type of anesthesia used might be important for the genesis of lung edema.

Effect of intraperitoneally administered hydrolyzed whey protein on blood pressure and renal sodium handling in awake spontaneously hypertensive rats

The present study evaluated the acute effect of the intraperitoneal (ip) administration of a whey protein hydrolysate (WPH) on systolic arterial blood pressure (SBP) and renal sodium handling by conscious spontaneously hypertensive rats (SHR). The ip administration of WPH in a volume of 1 ml dose-dependently lowered the SBP in SHR 2 h after administration at doses of 0.5 g/kg (0.15 M NaCl: 188.5 +/- 9.3 mmHg vs WPH: 176.6 +/- 4.9 mmHg, N = 8, P = 0.001) and 1.0 g/kg (0.15 M NaCl: 188.5 +/- 9.3 mmHg vs WPH: 163.8 +/- 5.9 mmHg, N = 8, P = 0.0018). Creatinine clearance decreased significantly (P = 0.0084) in the WPH-treated group (326 +/- 67 microL min-1 100 g body weight-1) compared to 0.15 M NaCl-treated (890 +/- 26 microL min-1 100 g body weight-1) and captopril-treated (903 +/- 72 microL min-1 100 g body weight-1) rats. The ip administration of 1.0 g WPH/kg also decreased fractional sodium excretion to 0.021 +/- 0.019% compared to 0.126 +/- 0.041 and 0.66 +/- 0.015% in 0.15 M NaCl and captopril-treated rats, respectively (P = 0.033). Similarly, the fractional potassium excretion in WPH-treated rats (0.25 +/- 0.05%) was significantly lower (P = 0.0063) than in control (0.91 +/- 0.15%) and captopril-treated rats (1.24 +/- 0.30%), respectively. The present study shows a decreased SBP in SHR after the administration of WPH associated with a rise in tubule sodium reabsorption despite an angiotensin I-converting enzyme (ACE)-inhibiting in vitro activity (IC50 = 0.68 mg/mL). The present findings suggest a pathway involving ACE inhibition but measurements of plasma ACE activity and angiotensin II levels are needed to support this suggestion.

Expression and localization of NK(1)R, substance P and CGRP are altered in dorsal root ganglia neurons of spontaneously hypertensive rats (SHR)

The kidneys play a pivotal role in the pathogenesis of essential hypertension because of a primary defect in renal hemodynamics and/or tubule hydro-saline handling that results in the retention of fluid and electrolytes. Previous studies have shown that increasing the renal pelvic pressure increased ipsilateral afferent renal nerve activity (ARNA), the ipsilateral renal pelvic release of substance P (SP) and the contralateral urinary sodium excretion in Wistar--Kyoto rats (WKy). However, spontaneously hypertensive rats (SHR) present an impaired renorenal reflex activity associated, partly, with a peripheral defect at the level of the sensory receptors in the renal pelvis. Furthermore, the renal pelvic administration of SP failed to increase ARNA in most of SHR at concentrations that produced marked increases in WKy. Since we have assessed the expression and localization of NK(1) receptor (NK(1)R), SP and calcitonin gene-related peptide (CGRP) in different dorsal root ganglia (DRG) cell subtypes and renal pelvis of 7- and 14-week-old SHR. The results of this study show increased SP and CGRP expression in the dorsal ganglia root cells of SHR compared to WKy rats. Additionally, there was a progressive, significant, age-dependent, decrease in NK(1)R expression on the membrane surface in SHR DRG cells and in the renal pelvis. In conclusion, the results of the present study suggest that the impaired activation of renal sensory neurons in SHR may be related to changes in the expression of neuropeptides and/or to a decreased presence of NK(1)R in DRG cells. Such abnormalities could contribute to the enhanced sodium retention and elevation of blood pressure seen in SHR.

Early altered renal sodium handling determined by lithium clearance in spontaneously hypertensive rats (SHR): Role of renal nerves

The mechanism by which blood pressure rises in the SHR strain remains to be elucidated. Since the long-term changes in renal sodium tubule handling associated with genetic hypertension have not been examined in detail, we hypothesized that SHR hypertension development may result from sustained renal sympathetic nerve overactivity and consequently decreased urinary sodium excretion. To test this hypothesis, we assessed renal sodium handling and cumulative sodium balance for 10 consecutive weeks in unanesthetized renal-denervated SHR, performed prior to the start of the entire 10-week metabolic studies, and their age-matched normotensive and hypertensive controls. The present investigation shows that SHR excreted less sodium than Wistar-Kyoto (WKy) rats during the initial 3-week observation period (p <0.05). This tendency was reversed when SHR were 10-wk old. Fractional urinary sodium excretion (FENa+) was significantly lower in 3 and 6-wk-old SHR when compared with the WKy age-matched group, as follows: SHR3-wk-old: 0.33 +/- 0.09% and WKy3-wk-old: 0.75 +/- 0.1% (P <0.05); SHR(6-wk-old): 0.52 +/- 0.12% and WKy6-wk-old: 0.83 +/- 0.11%. The decreased FENa+ in young SHR was accompanied by a significant increase in proximal sodium reabsorption (FEPNa+) compared with the normotensive age-matched control group (P <0.01). This increase occurred despite unchanged creatinine clearance (CCr) and fractional post-proximal sodium excretion (FEPPNa+)in all groups studied. The decreased urinary sodium excretion response in SHR up to the age of 6 weeks was significantly eradicated by bilateral renal denervation of SHR3-wk-old: 0.33 +/- 0.09% and SHR6-wk-old: 0.52 +/- 0.12% to DxSHR 3-wk-old: 1.02 +/- 0.2% and DxSHR 6-wk-old: 0.94 +/- 0.2% (P <0.01), in renal denervated rats. The current data suggest that neural pathways may play an instrumental role on renal sodium reabsorption as result of sustained sympathetic nervous system overexcitability.

Selective impairment of insulin signalling in the hypothalamus of obese Zucker rats

AIM/HYPOTHESIS

By acting in the brain, insulin suppresses food intake. However, little is known with regard to insulin signalling in the hypothalamus in insulin-resistant states.

METHODS

Western blotting, immunohistochemistry and polymerase chain reaction assays were combined to compare in vivo hypothalamic insulin signalling through the PI3-kinase and MAP kinase pathways between lean and obese Zucker rats.

RESULTS

Intracerebroventricular insulin infusion reduced food intake in lean rats to a greater extent than that observed in obese rats, and pre-treatment with PI3-kinase inhibitors prevented insulin-induced anorexia. The relative abundance of IRS-2 was considerably higher than that of IRS-1 in hypothalamus of both lean and obese rats. Insulin-stimulated phosphorylation of IR, IRS-1/2, the associations of PI 3-kinase to IRS-1/2 and phosphorylation of Akt in hypothalamus were decreased in obese rats compared to lean rats. These effects seem to be mediated by increased phosphoserine content of IR, IRS-1/2 and decreased protein levels of IRS-1/2 in obese rats. In contrast, insulin stimulated the phosphorylation of MAP kinase equally in lean and obese rats.

CONCLUSION/INTERPRETATION

This study provides direct measurements of insulin signalling in hypothalamus, and documents selective resistance to insulin signalling in hypothalamus of Zucker rats. These findings provide support for the hypothesis that insulin could have anti-obesity actions mediated by the PI3-kinase pathway, and that impaired insulin signalling in hypothalamus could play a role in the development of obesity in this animal model of insulin-resistance.

Effect of intracerebroventricularly injected insulin on urinary sodium excretion by cerebroventricular streptozotocin-treated rats

Recent evidence suggests that insulin may influence many brain functions. It is known that intracerebroventricular (icv) injection of nondiabetogenic doses of streptozotocin (STZ) can damage insulin receptor signal transduction. In the present study, we examined the functional damage to the brain insulin receptors on central mechanisms regulating glomerular filtration rate and urinary sodium excretion, over four periods of 30 min, in response to 3 microl insulin or 0.15 NaCl (vehicle) injected icv in STZ-treated freely moving Wistar-Hannover rats (250-300 g). The icv cannula site was visually confirmed by 2% Evans blue infusion. Centrally administered insulin (42.0 ng/ micro l) increased the urinary output of sodium (from 855.6 85.1 to 2055 310.6 delta%/min; N = 11) and potassium (from 460.4 100 to 669 60.8 delta%/min; N = 11). The urinary sodium excretion response to icv insulin microinjection was markedly attenuated by previous central STZ (100 micro g/3 micro l) administration (from 628 45.8 to 617 87.6 delta%/min; N = 5) or by icv injection of a dopamine antagonist, haloperidol (4 micro g/3 micro l) (from 498 +/- 39.4 to 517 +/- 73.2 delta%/min; N = 5). Additionally, insulin-induced natriuresis occurred by increased post-proximal tubule sodium rejection, despite an unchanged glomerular filtration rate. Excluding the possibility of a direct action of STZ on central insulin receptor-carrying neurons, the current data suggest that the insulin-sensitive response may be processed through dopaminergic D1 receptors containing neuronal pathways.

Acute intracerebroventricular insulin microinjection after nitric oxide synthase inhibition of renal sodium handling in rats

The role of the central nervous system (CNS) in the control of hydrosaline homeostasis has been strikingly demonstrated by several studies. Recent and growing evidence suggests that insulin or a nonapeptide-derived from the C-terminus of the insulin beta-chain may influence many brain functions. However, there is little information on the insulin-activated neural pathways regulating urinary sodium excretion. Also, we examined the influence of nitric oxide synthase activity by chronic oral administration of N(omega)-nitro-l-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthesis, after previous i.c.v. administration of insulin to unanesthetized, unrestrained rats that were randomly assigned to one of seven separated groups: (a) i.c.v. 0.15 M NaCl-injected (n = 11) and i.c.v. 126 ng (n = 11) insulin-injected rats; (b) i.c.v. insulin-injected in systemic L-NAME-treated (n = 10) and vehicle-treated insulin-injected rats (n = 10); and (c) subcutaneously (SC) insulin-injected rats (n = 5). We showed that centrally administered insulin produced increase in the urinary output of sodium (from 0.15 M NaCl: 855.6 +/- 85.1 Delta%.min(-1) to 126 ng insulin: 2055 +/- 310.6 Delta%.min(-1)) and potassium (126 ng: from 0.15 M NaCl: 460.4 +/- 100 Delta%.min(-1) to 126 ng insulin: 669 +/- 60.8 Delta%.min(-1)). The urinary sodium excretion response to i.c.v. 126 ng insulin microinjection was significantly abolished by previous systemic treatment of animals with 15 mg/kg/day L-NAME (from vehicle + 126 ng insulin: 1935 +/- 258.3 Delta%. min(-1) to L-NAME + 126 ng insulin: 582.3 +/- 69.6 Delta%. min(-1)). In addition, we showed that insulin-induced natriuresis occurred by increasing post-proximal tubule sodium rejection (FEPP(Na)), despite an unchanged glomerular filtration rate (C(Cr)). The current data suggests the novel concept that CNS NO-dependent neural pathways may play an instrumental role on efferent insulin-sensitive nerve activity from periventricular region. Speculatively, it seems interesting to suggest that perhaps one of the efferent signals triggered by insulin in the CNS may be nitrergic in nature, and that defects in this efferent signal could result in insulin central resistance, inability of renal tubules to handle the hydro electrolyte balance and hypertension.

Effect of the crude extract of Vernonia polyanthes Less. on blood pressure and renal sodium excretion in unanesthetized rats

This study evaluated the effect of oral crude Vernonia polyanthes Less. hydroalcoholic extract administration (CHE, 0.5 and 1.0 g/kg body wt., daily for 7 days) on arterial blood pressure and renal sodium excretion in conscious rats. CHE administration decreased arterial blood pressure dose-dependently followed by a significant rise in creatinine clearance and a fall in fractional post-proximal sodium excretion was compared to the control group. These results suggest that blood pressure decrease induced by the oral crude Vernonia hydroalcoholic extract may be blunted by reduction of the post-proximal renal sodium excretion. Thus, the present study shows that Vernonia extract is a potential vasodilatation agent in normotensive rats without any effects on renal tubule autoregulation mechanisms.

Bothrops moojeni snake venom-induced renal glomeruli changes in rat

The venom of Bothrops moojeni has potent proteolytic and phospholipase A2 activities. In previous work, we showed that intravenous injection of this venom in rats decreased creatinine clearance and caused tubular dysfunction and histopathological changes with no alterations in blood pressure. The current study used scanning and transmission electron microscopy to assess the ultrastructural changes caused by B. moojeni venom (0.4 mg/kg i.v.) in rat renal glomeruli and correlated these alterations with the severity of proteinuria 5 hours, 16 hours, and 48 hours after venom injection. The changes included mesangiolysis, glomerular microaneurysms, and glomerular basement membrane (GBM) abnormalities. In addition, there was a reduction in the number and width of podocyte pedicels, which caused a reduction in the number of filtration slits. Electron-dense amorphous material, which may be proteinaceous in origin, was found in the pedicels. The severity of the ultrastructural abnormalities correlated with the level of proteinuria. These morphophysiological changes were attributed to biochemical and physiological disturbances in the components of the GBM and mesangial matrix as well as in cytoskeleton-associated proteins of podocytic processes, and could account for the breakdown of optimal glomerular filtration barrier functioning. These results, together with the absence of appreciable glomerular fibrin deposits, support the hypothesis of a direct activity of B. moojeni venom on rat kidneys. Proteolytic activity of the venom on renal glomeruli could then contribute to the onset of acute renal failure, and would explain the clinical manifestations of renal injury after bites by this and other Bothrops species.

Effects of intracerebroventricular insulin microinjection on renal sodium handling in kidney-denervated rats

The role of the central nervous system (CNS) in the control of hydrosaline homeostasis has been strikingly demonstrated by several studies. Growing evidence suggests that insulin may exert an influence in the modulation of many brain functions. However, there are no available data examining the CNS effect of insulin injection on renal sodium handling. Also, to examine the influence of renal nerve activity during i.c.v. administration of insulin, unanesthetized, unrestrained rats were randomly assigned to one of nine separated groups: (a) sham-operated i.c.v. 0.15 M NaCl-injected (Co, pooled data, n = 37) and sham-operated i.c.v. 0.42 ng. microl(-1) (n = 12), 4.2 ng.microl(-1) (n = 10) and 42.0 ng.microl(-1) (n = 11) insulin-injected rats (In); (b) renal-denervated i.c.v. 0.15 M NaCl (Co(Dx), n = 5), and insulin-injected rats (In(Dx), n = 5); and (c) subcutaneously insulin-injected rats (SC, n = 5). We showed that centrally administered insulin produced dose-related increased urinary output of sodium [Co: 855 +/- 85 Delta% min, 0.42 ng.microl(-1) In: 1189 +/- 308 Delta% min, 4.2 ng.microl(-1) In: 1461 +/- 594 Delta% min (p = 0.048), and 42.0 ng.microl(-1) In: 2055 +/- 411 Delta% min (p = 0.0001)], and dose-independently increased potassium excretion [Co: 460 +/- 28 Delta% min, 0.42 ng.microl(-1) In: 649 +/- 100 Delta% min (p = 0.016), 4.2 ng.microl(-1) In: 671 +/- 175 Delta% min (p = 0.003), and 42.0 ng.microl(-1) In: 669 +/- 70 Delta% min (p = 0.002)] compared to control. The urinary sodium excretion response to i.c.v. 42 ng.microl(-1) insulin injections were abolished by bilateral renal denervation. In addition, we showed that insulin-induced natriuresis occurred by increasing postproximal tubule sodium rejection (FEPP(Na)), and changed glomerular filtration rate (C(Cr)) at 42.0 ng.microl(-1) (p = 0.023) i.c.v. insulin microinjection but not at smaller insulin dose. The current data suggests that a blunted efferent insulin-sensitive nerve activity from periventricular region may contribute to the inability of renal tubules to handle the hydroelectrolyte balance.