ANP and BNP responses to dehydration in the one-humped camel and effects of blocking the renin-angiotensin system

Plasma N-terminal pro-atrial natriuretic peptide concentrations are affected by dehydration in healthy dogs

Background

Plasma N-terminal pro-atrial natriuretic peptide (NT-proANP) and plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations may be affected by the hydration status.

Aim

This study aimed to evaluate the effect of dehydration on plasma NT-proANP and NT-proBNP concentrations in healthy dogs.

Methods

This prospective study included five clinically healthy dogs. Furosemide was administered intravenously at 2-4 mg/kg every 1-2 hours until completion of the dehydration model. The dehydration model was considered complete when weight loss was ≥5% and findings of dehydration on physical examination were observed. Plasma NT-proANP and NT-proBNP concentrations were compared at three-time points: before the dehydration model was created (point 1), at the completion of the dehydration model (point 2), and when dehydration was judged to have improved (point 3). Association between plasma NT-proANP and NT-proBNP concentrations, and each clinical variable (physical examination, blood pressure, blood chemistry, blood gases, and echocardiography) was assessed using linear regression analysis.

Results

Plasma NT-proANP concentration decreased significantly from point 2 to point 1 (p < 0.05), whereas plasma NT-proBNP concentration showed a decreasing trend but did not differ significantly between points 1 and 2. Plasma NT-proANP concentration correlated significantly with body weight (R² = 0.178) and plasma NT-proBNP concentration (R² = 0.284) (p < 0.05, respectively), and plasma NT-proBNP concentration correlated significantly with electrolytes (sodium, R² = 0.439; potassium, R² = 0.444; and chloride, R² = 0.419), and echocardiographic parameters [diastolic left ventricular internal diameter (LVIDd) R² = 0.519; weight-standardized LVIDd, R² = 0.535] (p < 0.01, respectively).

Conclusion

The plasma NT-proANP concentrations decreased with dehydration. However, the plasma NT-proBNP concentration did not change with mild dehydration and reflected left ventricular morphology.

Comparative physiological, morphological, histological, and AQP2 immunohistochemical analysis of the Arabian camels (Camelus dromedarius) and oxen kidney: Effects of adaptation to arid environments

Compared to other mammals, Arabian camels are ideal models for exploring the structural adaptations that enable camels to survive in arid environments. Thus, this study aimed to explore how evolutionary adaptation to arid conditions modifies the characteristics of the kidneys in Arabian camels (Camelus dromedarius) compared to oxen. Urine samples were physically and chemically analyzed. Harvested kidneys were subjected to topographical and fast spin echo magnetic resonance (FSE-MR) imaging. Histology, histomorphometry, and Aquaporin-2 (AQP2) expression by immunohistochemistry were also performed. Here, in dromedaries, sodium and potassium values in the urine were much higher (p=0.001, for both), whereas chloride was much lower (p=0.004) than the values of oxen. Compared with oxen, the level of the hormone aldosterone in serum was significantly lower (p=0.002), whereas creatinine and urea were significantly higher (p=0.005 and p=0.001, respectively). Uric acid in dromedaries and oxen did not differ significantly (p=0.349). Like sodium levels (p=0.001) in dromedary serum, chloride was also much higher (p=0.002) than in oxen. The average value of potassium was much lower (p=0.009) than that of oxen. Morphologically, anatomical and FSE MRI studies revealed that minor and major calyces were not found in dromedary kidneys. The renal pelvis was not found in oxen, and the major calyx was directly connected to the ureter. The dromedary kidney contained a wider medullary portion as well as increased diameters for renal corpuscles (RCs), proximal convoluted tubules (PCTs), and collecting tubules (CTs, p&lt;0.05) compared with the oxen. We also noted that AQP2 was significantly expressed in dromedary nephron components, except for RCs, compared with oxen as shown by immunohistochemistry. Overall, these data strongly suggest that the dromedary has a greater ability to adapt to harsh desert conditions in terms of producing highly concentrated urine than oxen.

The effect of long-term dehydration and subsequent rehydration on markers of inflammation, oxidative stress and apoptosis in the camel kidney

Background

Dehydration has deleterious effects in many species, but camels tolerate long periods of water deprivation without serious health compromise. The kidney plays crucial role in water conservation, however, some reports point to elevated kidney function tests in dehydrated camels. In this work, we investigated the effects of dehydration and rehydration on kidney cortex and medulla with respect to pro-inflammatory markers, oxidative stress and apoptosis along with corresponding gene expression.

Results

The cytokines IL-1β and IL-18 levels were significantly elevated in the kidney cortex of dehydrated camel, possibly expressed by tubular epithelium, podocytes and/or mesangial cells. Elevation of IL-18 persisted after rehydration. Dehydration induced oxidative stress in kidney cortex evident by significant increases in MDA and GSH, but significant decreases in SOD and CAT. In the medulla, CAT decreased significantly, but MDA, GSH and SOD levels were not affected. Rehydration abolished the oxidative stress. In parallel with the increased levels of MDA, we observed increased levels of PTGS1 mRNA, in MDA synthesis pathway. GCLC mRNA expression level, involved in GSH synthesis, was upregulated in kidney cortex by rehydration. However, both SOD1 and SOD3 mRNA levels dropped, in parallel with SOD activity, in the cortex by dehydration. There were significant increases in caspases 3 and 9, p53 and PARP1, indicating apoptosis was triggered by intrinsic pathway. Expression of BCL2l1 mRNA levels, encoding for BCL-xL, was down regulated by dehydration in cortex. CASP3 expression level increased significantly in medulla by dehydration and continued after rehydration whereas TP53 expression increased in cortex by rehydration. Changes in caspase 8 and TNF-α were negligible to instigate extrinsic apoptotic trail. Generally, apoptotic markers were extremely variable after rehydration indicating that animals did not fully recover within three days.

Conclusions

Dehydration causes oxidative stress in kidney cortex and apoptosis in cortex and medulla. Kidney cortex and medulla were not homogeneous in all parameters investigated indicating different response to dehydration/rehydration. Some changes in tested parameters directly correlate with alteration in steady-state mRNA levels.

A comparison of physiological and transcriptome responses to water deprivation and salt loading in the rat supraoptic nucleus

Salt loading (SL) and water deprivation (WD) are experimental challenges that are often used to study the osmotic circuitry of the brain. Central to this circuit is the supraoptic nucleus (SON) of the hypothalamus, which is responsible for the biosynthesis of the hormones, arginine vasopressin (AVP) and oxytocin (OXT), and their transport to terminals that reside in the posterior lobe of the pituitary. On osmotic challenge evoked by a change in blood volume or osmolality, the SON undergoes a function-related plasticity that creates an environment that allows for an appropriate hormone response. Here, we have described the impact of SL and WD compared with euhydrated (EU) controls in terms of drinking and eating behavior, body weight, and recorded physiological data including circulating hormone data and plasma and urine osmolality. We have also used microarrays to profile the transcriptome of the SON following SL and remined data from the SON that describes the transcriptome response to WD. From a list of 2,783 commonly regulated transcripts, we selected 20 genes for validation by qPCR. All of the 9 genes that have already been described as expressed or regulated in the SON by osmotic stimuli were confirmed in our models. Of the 11 novel genes, 5 were successfully validated while 6 were false discoveries.

Correlations of ANP genetic polymorphisms and serum levels with ischemic stroke risk: a meta-analysis

AIMS

This meta-analysis was performed to evaluate the correlations between atrial natriuretic peptide (ANP) genetic polymorphism and its serum ANP levels with the risk of ischemic stroke.

METHODS

The PubMed, CISCOM, CINAHL, Web of Science, Google Scholar, EBSCO, Cochrane Library, and CBM databases were searched for relevant articles published before October 1st, 2013 without language restrictions. Meta-analysis was conducted using the STATA 12.0 software. Crude odds ratios (ORs) or standardized mean difference (SMD) with their 95% confidence interval (95% CI) were calculated. Twelve case-control studies that met all inclusion criteria were included in this meta-analysis. A total of 1285 patients with ischemic stroke and 1088 healthy control subjects were involved in this meta-analysis. Three common single-nucleotide polymorphisms (1837 G/A, 2238 T/C, and 664 G/A) in the ANP gene were assessed.

RESULTS

Our meta-analysis results revealed that ANP 2238 T/C polymorphism might increase the risk of ischemic stroke (C allele vs. T allele: OR=2.26, 95% CI: 1.59-3.23, p<0.001; TC+CC vs. TT: OR=2.26, 95% CI: 1.34-3.81, p=0.002; respectively). However, we found no correlations of ANP 1837 G/A and 664 G/A polymorphisms with ischemic stroke risk (all p>0.05). Furthermore, ischemic stroke patients had higher levels of serum ANP than those of healthy control subjects (SMD=3.12, 95% CI: 1.16-5.07, p=0.002). Our study revealed no publication bias in this meta-analysis (all p>0.05).

CONCLUSION

Our findings indicate that ANP genetic polymorphism and serum ANP levels may contribute to the development of ischemic stroke. Thus, the ANP genetic polymorphism and serum ANP levels could be potential biomarkers for early detection of ischemic stroke.

Effects of dehydration and blockade of angiotensin II AT1 receptor on stress hormones and anti-oxidants in the one-humped camel

Background

The objective of this study was to provide for the first time data on plasma catecholamines, cortisol, glutathione and malondialdehyde after long term dehydration (20 days) in the presence and absence of angiotensin II (Ang II) AT1 receptor blocker (losartan) versus levels in time-matched, non-dehydrated control camels and to record the responses of glutathione and malondialdehyde activity in liver and kidney homogenates in control, dehydrated-losartan treated and dehydrated camels. Eighteen male camels were studied, six hydrated (control group), six dehydrated and treated with losartan (treated group) and six dehydrated not treated (dehydrated).

Results

Plasma levels of norepinephrine and dopamine were significantly increased (P < 0.01) in both treated and dehydrated groups compared to time matched control, whereas Plasma epinephrine level showed significant decrease (P < 0.05) in both treated and dehydrated groups compared to control. Plasma cortisol also showed significant increase (P < 0.01) in both treated and dehydrated groups compared to control. Glutathione levels in plasma, liver and kidney homogenates for both treated and dehydrated groups reveled significant increase (P < 0.05) Likewise, malondialdehyde levels in plasma, liver and kidney homogenates were substantially and significantly increased in both treated and dehydrated groups.

Conclusion

In conclusion, the results of this study demonstrated that dehydration substantially increased the circulating levels of norepinephrine, dopamine and cortisol but decreased plasma epinephrine. Similarly, losartan showed similar effects to that of dehydration. In addition, this investigation showed dehydration alone or in combination with losartan induced significant increments in glutathione and malondialdehyde activities in plasma, liver and kidney homogenates, presumably in order to counteract the potentially damaging effects of free radicals. Blockade of angiotensin II AT1 receptors did not alter significantly the response of dehydration in any of these indices.