Water Efflux Research Articles

Differential responses in ammonia excretion, sodium fluxes and gill permeability explain different sensitivities to acute high environmental ammonia in three freshwater teleosts

We examined the acute physiological responses to high environmental ammonia (HEA), particularly the linkages between branchial ammonia fluxes and unidirectional Na+ fluxes, as well as urea excretion, cortisol, and indicators of gill permeability in three freshwater teleosts differing in their sensitivities to ammonia; the highly sensitive salmonid Oncorhynchus mykiss (rainbow trout), the less sensitive cyprinid Cyprinus carpio (common carp) and the highly resistant cyprinid Carassius auratus (goldfish). Fish were acutely exposed to two sub-lethal ammonia concentrations (as NH4HCO3) at pH 7.9: 1mM for a period of 12h, identical for all species, and 5mM for the cyprinids and 1.4mM for the trout for 3h. Elevation of plasma cortisol at both levels of HEA was apparent in all species. At 1mM, ammonia excretion (Jamm) was inhibited to a greater extent in trout than cyprinids and concurrently a significantly higher plasma ammonia level was evident in trout. However Jamm was reversed in all species at 5 or 1.4mM. Goldfish showed a significant increase in urea excretion rate (Jurea) during HEA exposure. In carp and trout, neither level of HEA elevated Jurea but urea production was increased as evidenced by a considerable elevation of plasma urea. At 1mM HEA, Na+ imbalance became progressively more severe in trout and carp due to a stimulation of unidirectional Na+ efflux (JoutNa) without a concomitant increase in unidirectional Na+ influx (JinNa). Additionally, a transient reduction of JinNa was evident in trout. Goldfish showed an opposite trend for JoutNa with reduced efflux rates and a positive Na+ balance during the first few hours of HEA. However, after 12h of exposure, both JinNa and JoutNa were also increased in both carp and goldfish, whereas only JoutNa was increased in trout, leading to a net Na+ loss. Na+ homeostasis was entirely disrupted in all three species when subjected to the 5 or 1.4mM ammonia for 3h: JinNa was significantly inhibited while considerable activation of JoutNa was observed. Diffusive water efflux rates and net K+ loss rates across the gills were enhanced during HEA only in trout, indicating an increment in gill transcellular permeability. Transepithelial potential was increased in all the species during ammonia exposure, but to the least extent in goldfish. Overall, for several different physiological systems, trout were most disturbed, and goldfish were least disturbed by HEA, helping to explain the differential ammonia tolerance of the three species.

Interaction of xylem and phloem during exudation and wound occlusion in Cucurbita maxima

Collection of cucurbit exudates from cut petioles has been a powerful tool for gaining knowledge on phloem sap composition without full notion of the complex exudation mechanism. Only few publications explicitly mentioned that exudates were collected from the basal side of the cut, which exudes more copiously than the apical side. This is surprising since only exudation from the apical side is supposedly driven by phloem pressure gradients. Composition of carbohydrates and pH values at both wounding sides are equal, whereas protein concentration is higher at the basal side. Apparently, exudation is far more complex than just the delivery of phloem sap. Xylem involvement is indicated by lower protein concentrations after elimination of root pressure. Moreover, dye was sucked into xylem vessels owing to relaxation of negative pressure after cutting. The lateral water efflux from the vessels increases turgor of surrounding cells including sieve elements. Simultaneously, detached parietal proteins (PP1/PP2) induce occlusion of sieve plates and cover wound surface. If root pressure is strong enough, pure xylem sap can be collected after removal of the occlusion plug at the wound surface. The present findings provide a mechanism of sap exudation in Cucurbita maxima, in which the contribution of xylem water is integrated.

Cholera: Something Old, Something New

In the aftermath of a devastating earthquake in early 2011, Haiti fell victim to an outbreak of cholera that claimed thousands of lives and affected populations in nearby Dominican Republic, Venezuela, and even the United States. This was the first time cholera had been reported in Haiti in more than 100 years. The sudden appearance of cholera, a pathogen with no known non-human host, raised the question of how it was introduced to an island that has long been spared this disease. The purpose of this review is to provide an overview of the history of cholera, its pathophysiology and virulence factors, and current recommendations for treatment. Articles published in the past 10 years were identified by a search of the medical literature using PUBMED and reviewed. Bibliographies of each article also were reviewed for additional pertinent articles. The recent epidemic was caused by a strain that has been responsible for disease in South Asia since 1961, the seventh and most recent strain identified since 1900. It is transmitted by the fecal-oral route. Once infected, the patient develops a rapidly dehydrating diarrheal illness caused by the cholera toxin, which activates cytoplasmic adenylate cyclase of the intestinal epithelial cells by adenosine diphosphate (ADP)-ribosylation of the stimulatory G protein. The high cyclic adenosine monophosphate (cAMP) concentrations activate the cystic fibrosis transmembrane conductance regulator, causing a dramatic efflux of ions and water from infected enterocytes and leading to watery diarrhea. The first line of therapy is oral hydration with intravenous fluids; antibiotics are reserved for patients with severe dehydration. Spread of cholera is preventable with simple modifications of hygiene and water preparation. Cholera has re-emerged as a major infectious disease in the recent past, with a global increase in its incidence. Vaccination should be considered as an adjunct for controlling the epidemics and also for volunteer health care workers who provide services to underdeveloped nations. During an epidemic such as occurred in Haiti, use of antibiotics should be considered for all hospitalized patients. These endeavors should proceed in concert with much-needed improvements in sanitation and accessibility of potable water.

Analysis of xylem sap from functional (nonembolized) and nonfunctional (embolized) vessels of Populus nigra: chemistry of refilling.

It is assumed that the refilling of drought-induced embolism requires the creation of an osmotic gradient between xylem parenchyma cells and vessel lumens to generate the water efflux needed to fill the void. To assess the mechanism of embolism repair, it is crucial to determine if plants can up-regulate the efflux of osmotically active substances into embolized vessels and identify the major components of the released osmoticum. Here, we introduce a new approach of sap collection designed to separate water from nonembolized (functional) and embolized (nonfunctional) vessels. This new approach made possible the chemical analysis of liquid collected from both types of vessels in plants subjected to different levels of water stress. The technique also allowed us to determine the water volumes in nonfunctional vessels as a function of stress level. Overall, with the increase of water stress in plants, the osmotic potential of liquid collected from nonfunctional vessels increased while its volume decreased. These results revealed the presence of both sugars and ions in nonfunctional vessels at elevated levels in comparison with liquid collected from functional vessels, in which only traces of sugars were found. The increased sugar concentration was accompanied by decreased xylem sap pH. These results provide new insight into the biology of refilling, underlining the role of sugar and sugar transporters, and imply that a large degree of hydraulic compartmentalization must exist in the xylem during the refilling process.

Osmotic stress adaptations in rhizobacteria

Rhizobacteria have been reported to be beneficial to the plants in many different ways. Increasing salinity in the coastal agricultural zones has been shown to be a threat to the plant and microbial life in the area. Exposure of microorganisms to high-osmolality environments triggers rapid fluxes of cell water along the osmotic gradient out of the cell, thus causing a reduction in turgor and dehydration of the cytoplasm. The microorganisms have developed various adaptations to counteract the outflow of water. The first response to osmotic up shifts and the resulting efflux of cellular water is uptake of K⁺ and cells start to accumulate compatible solutes. Yet another mechanism is by altering the cell envelope composition resulting in changes in proteins, periplasmic glucans, and capsular, exo and lipopolysaccharides. Bacteria also initiate a program of gene expression in response to osmotic stress by high NaCl concentrations, which are manifested as a set of proteins produced in increased amounts in response to the stress. Genomics, transcriptomics and proteomics approaches have revealed the key components in molecular basis of bacteria salt adaptation. Understanding the mechanisms of osmo-adaptation in rhizobacteria would also be relevant from an ecological and an applicative point of view.

Fast, Multiphase Volume Adaptation to Hyperosmotic Shock by Escherichia coli

All living cells employ an array of different mechanisms to help them survive changes in extra cellular osmotic pressure. The difference in the concentration of chemicals in a bacterium's cytoplasm and the external environment generates an osmotic pressure that inflates the cell. It is thought that the bacterium Escherichia coli use a number of interconnected systems to adapt to changes in external pressure, allowing them to maintain turgor and live in surroundings that range more than two-hundred-fold in external osmolality. Here, we use fluorescence imaging to make the first measurements of cell volume changes over time during hyperosmotic shock and subsequent adaptation on a single cell level in vivo with a time resolution on the order of seconds. We directly observe two previously unseen phases of the cytoplasmic water efflux upon hyperosmotic shock. Furthermore, we monitor cell volume changes during the post-shock recovery and observe a two-phase response that depends on the shock magnitude. The initial phase of recovery is fast, on the order of 15–20 min and shows little cell-to-cell variation. For large sucrose shocks, a secondary phase that lasts several hours adds to the recovery. We find that cells are able to recover fully from shocks as high as 1 Osmol/kg using existing systems, but that for larger shocks, protein synthesis is required for full recovery.

The apical NKCC1 cotransporter debate

Choroid plexus epithelial cells (CPECs) secrete cerebrospinal fluid (CSF) and regulate its electrolyte composition. CPECs express Na+/K+ ATPase and Na+‐K+‐2Cl− cotransporter 1 (NKCC1) on their apical membrane (CSF‐facing), deviating from typical basolateral membrane location in secretory epithelia. Given this non‐canonical location of NKCC1 for a secretory epithelial cell, the direction of net ion fluxes mediated by this cotransporter and associated water fluxes, under physiological conditions, is controversial in CPECs. NKCC1‐mediated ion and water fluxes are tightly linked, thus their direction can be inferred by measuring cell volume changes following NKCC1 inactivation. Hypotheses: under physiological conditions NKCC1 is working in the uptake mode and maintains normal cell water volume in CPECs, hence knocking out NKCC1 will produce cell shrinkage due to unbalanced net efflux of solutes and water. Electron microscopy revealed NKCC1−/− CPECs are severely shrunken, forming large dilations of their basolateral extracellular spaces, yet remain attached by apical tight junctions. Nomarski microscopy confirmed that freshly dissociated CPECs from NKCC1−/− mice are half the size of CPECs from WT (p< 0.01). These results demonstrate that under physiological conditions NKCC1 is constitutively active, works in the uptake mode, and is necessary to maintain normal cell water volume.

The Role of Aquaporins in Water Balance in Cheilanthes lanosa (Adiantaceae) Gametophytes

Aquaporins are transmembrane proteins that move water specifically and bidirectionally in response to internal cell signaling. With aquaporins, plant cells can control how, where, and when water moves across membranes. Thus, plants are in strong control of their environmental responses. Therefore, it seems likely that aquaporins would have a key role in water balance in xerophytic ferns, particularly in the gametophyte stage. To investigate the role of aquaporins in desiccation avoidance in xerophytic ferns gametophytes, Cheilanthes lanosa gametophytes were poisoned with micromolar mercury solutions, which block aquaporin channels, exposed to several osmolytes, and quantified the efflux of water from the cells was quantified. Results strongly suggest that aquaporins may very well play a role in water balance, but also pose some questions concerning the ability of the protonemal stage to fully manage water flow.

Multiphase Recovery of Escherichia Coli to Hyperosmotic Shock

All living cells employ an array of different mechanisms to help them survive changes in extracellular osmotic pressure. The difference in the concentration of chemicals in a bacterium's cytoplasm and the external environment generates an osmotic pressure that inflates the cell. It is thought that the bacterium Escherichia coli uses a number of interconnected systems to adapt to changes in external pressure. This allows these cells to maintain turgor and live in surroundings that range more than two-hundred-fold in external osmolality. Here, we use fluorescence imaging to make the first measurements of cell volume changes over time during hyperosmotick shock and subsequent adaptation on a single cell level in vivo with a time resolution on the order of seconds. We directly observe two previously unseen phases of the cytoplasmic water efflux upon hyperosmotic shock and identify the mechanisms behind them. Furthermore, we monitor cell volume changes during the post-shock recovery and observe two different types of response that depend on the shock level, as well as two different recovery time scales. The initial phase of recovery is fast, on the order of 20 min, and proceeds even in the absence of the two potassium transporters TrkA(G/H) and KdpFABC. A protein-synthesis controlled mechanism then causes the cell to switch to a second, slower recovery phase that lasts on the order of several hours. Interestingly, the occurrence of this secondary phase requires the presence of both TrkA(G/H) and KdpFABC, suggesting that it is triggered by coordinated import of potassium using these two transporters.

The SEC6 protein is required for function of the contractile vacuole inChlamydomonas reinhardtii

Contractile vacuoles (CVs) are essential for osmoregulation in many protists. To investigate the mechanism of CV function in Chlamydomonas, we isolated novel osmoregulatory mutants. Four of the isolated mutant cell lines carried the same 33,641 base deletion, rendering the cell lines unable to grow under strong hypotonic conditions. One mutant cell line (Osmo75) was analyzed in detail. The CV morphology was variable in mutant cells, and most cells had multiple small CVs. In addition, one or two enlarged CVs or no visible CVs at all, were observed by light microscopy. These findings suggest that the mutant is impaired in homotypic vacuolar and exocytotic membrane fusion. Furthermore the mutants had long flagella. One of the affected genes is the only SEC6 homologue in Chlamydomonas (CreSEC6). The SEC6 protein is a component of the exocyst complex that is required for efficient exocytosis. Transformation of the Osmo75 mutant with a CreSEC6-GFP construct rescued the mutant completely (osmoregulation and flagellar length). Rescued strains overexpressed CreSEC6 (as a GFP-tagged protein) and displayed a modified CV activity. CVs were larger, whereas the CV contraction interval remained unchanged, leading to increased water efflux rates. Electron microscopy analysis of Osmo75 cells showed that the mutant is able to form the close contact zones between the plasma membrane and the CV membrane observed during late diastole and systole. These results indicate that CreSEC6 is essential for CV function and required for homotypic vesicle fusion during diastole and water expulsion during systole. In addition, CreSEC6 is not only necessary for CV function, but possibly influences the CV cycle in an indirect manner and flagellar length in Chlamydomonas.

Impact of Body Reserves on Energy Expenditure, Water Flux, and Mating Success in Breeding Male Northern Elephant Seals

In capital breeders, individual differences in body size and condition can impact mating effort and success. In addition to the collateral advantages of large body size in competition, large nutrient reserves may offer advantages in endurance rivalry and enable the high rates of energy expenditure associated with mating success. We examined the impacts of body reserves and dominance rank on energy expenditure, water flux, mating success, and breeding tenure in the adult male northern elephant seal, a polygynous, capital breeder. Adult males expended energy at a rate of 159 ± 49 MJ d (-1), which is equivalent to 3.1 times the standard metabolic rate predicted by Kleiber's equation. Despite high rates of energy expenditure and a long fasting duration, males spared lean tissue effectively, deriving a mean of 7% of their metabolism from protein catabolism. Body composition had a strong impact on the ability to spare lean tissue during breeding. When controlling for body size, energy expenditure, depletion of blubber reserves, and water efflux were significantly greater in alpha males than in subordinate males. Large body size was associated with increased reproductive effort, tenure on shore, dominance rank, and reproductive success. Terrestrial locomotion and topography appeared to strongly influence energy expenditure. Comparisons with conspecific females suggest greater total seasonal reproductive effort in male northern elephant seals when controlling for the effects of body mass. In polygynous capital breeding systems, male effort may be strongly influenced by physiological state and exceed that of females.

Generalization of experimental data on two-phase critical efflux through axisymmetric channels

The results of studying the characteristics of a two-phase flow being formed during adiabatic water efflux through axisymmetric cylindrical and Laval nozzle channels are presented. Experiments were carried out with saturated water in the range of initial pressures 0.6–4.0 MPa. The fluid efflux was performed into the air with atmospheric pressure. The generalizing relations for calculating thrust pulse and critical flowrate were obtained.

Active Trans-Plasma Membrane Water Cycling in Yeast Is Revealed by NMR

Plasma membrane water transport is a crucial cellular phenomenon. Net water movement in response to an osmotic gradient changes cell volume. Steady-state exchange of water molecules, with no net flux or volume change, occurs by passive diffusion through the phospholipid bilayer and passage through membrane proteins. The hypothesis is tested that plasma membrane water exchange also correlates with ATP-driven membrane transport activity in yeast (Saccharomyces cerevisiae). Longitudinal 1H2O NMR relaxation time constant (T1) values were measured in yeast suspensions containing extracellular relaxation reagent. Two-site-exchange analysis quantified the reversible exchange kinetics as the mean intracellular water lifetime (τi), where τi−1 is the pseudo-first-order rate constant for water efflux. To modulate cellular ATP, yeast suspensions were bubbled with 95%O2/5%CO2 (O2) or 95%N2/5%CO2 (N2). ATP was high during O2, and τi−1 was 3.1 s−1 at 25°C. After changing to N2, ATP decreased and τi−1 was 1.8 s−1. The principal active yeast ion transport protein is the plasma membrane H+-ATPase. Studies using the H+-ATPase inhibitor ebselen or a yeast genetic strain with reduced H+-ATPase found reduced τi−1, notwithstanding high ATP. Steady-state water exchange correlates with H+-ATPase activity. At volume steady state, water is cycling across the plasma membrane in response to metabolic transport activity.

Aquaporin inhibition changes protein phosphorylation pattern following sperm motility activation in fish

Our previous studies demonstrated that osmolality is the key signal in sperm motility activation in Sparus aurata spermatozoa. In particular, we have proposed that the hyper-osmotic shock triggers water efflux from spermatozoa via aquaporins. This water efflux determines the cell volume reduction and, in turn, the rise in the intracellular concentration of ions. This increase could lead to the activation of adenylyl cyclase and of the cAMP-signaling pathway, causing the phosphorylation of sperm proteins and then the initiation of sperm motility. This study confirms the important role of sea bream AQPs (Aqp1a and Aqp10b) in the beginning of sperm motility. In fact, when these proteins are inhibited by HgCl2, the phosphorylation of some proteins (174 kDa protein of head; 147, 97 and 33 kDa proteins of flagella), following the hyper-osmotic shock, was inhibited (totally or partially). However, our results also suggest that more than one transduction pathways could be activated when sea bream spermatozoa were ejaculated in seawater, since numerous proteins showed an HgCl2(AQPs)-independent phosphorylation state after motility activation. The role played by each different signal transduction pathways need to be clarified.

The promotion of drug rectal absorption by water absorption.

The promotion of the rectal absorption of antipyrine by sodium taurocholate (TC-Na) or sodium ethylenediaminetetraacetate (EDTA-Na) has been examined by in-situ recirculating perfusion in the rat. These promoters significantly increased water influx, efflux and antipyrine absorption clearance (CLAP). Ouabain treatment significantly reduced the increase in both rectal absorption of drug and water flux. Water absorption dependent on active sodium transport may thus possibly promote the rectal absorption of poorly absorbable drugs.

Two applications of the thermogram of the alcohol/water binary system with compositions of cryobiological interests

Quantitative analyses of the bound water content in the alcohol aqueous solution and its osmotic behavior should be cryobiologically significant. This paper has presented two applications of the thermogram of the alcohol/water system recorded by differential scanning calorimeter (DSC). Both applications are: (1) generating the quantitative relationship between the bound water content and the solution composition; (2) calculating the osmotic virial coefficients for alcohols. Five alcohols including methanol, ethanol, ethylene glycol, propylene glycol and glycerol are investigated. In the present study, partial binary phase diagrams of these five alcohol solutions are determined in the first place. The bound water contents in these solutions are quantitatively evaluated by three criteria afterwards. In the end, the osmotic virial coefficients for these alcohols are calculated according to the osmotic virial equation. It is turned out that the bound water fraction out of the total water content increases with a rising molality. The ability of the solute to restrict water molecules can be weakened when the solution becomes more concentrated. The results also indicate that propylene glycol should be the strongest “water-blocker” while methanol the weakest one. These findings can deepen our understanding of the cryoprotective properties of the alcohols from the perspectives of their roles in binding free water and promoting the osmotic efflux of cell water.

Mechanisms of Water Transport Mediated by PIP Aquaporins and Their Regulation Via Phosphorylation Events Under Salinity Stress in Barley Roots

Water homeostasis is crucial to the growth and survival of plants under water-related stress. Plasma membrane intrinsic proteins (PIPs) have been shown to be primary channels mediating water uptake in plant cells. Here we report the water transport activity and mechanisms for the regulation of barley (Hordeum vulgare) PIP aquaporins. HvPIP2 but not HvPIP1 channels were found to show robust water transport activity when expressed alone in Xenopus laevis oocytes. However, the co-expression of HvPIP1 with HvPIP2 in oocytes resulted in significant increases in activity compared with the expression of HvPIP2 alone, suggesting the participation of HvPIP1 in water transport together with HvPIP2 presumably through heteromerization. Severe salinity stress (200 mM NaCl) significantly reduced root hydraulic conductivity (Lp(r)) and the accumulation of six of 10 HvPIP mRNAs. However, under relatively mild stress (100 mM NaCl), only a moderate reduction in Lp(r) with no significant difference in HvPIP mRNA levels was observed. Sorbitol-mediated osmotic stress equivalent to 100 and 200 mM NaCl induced nearly identical Lp(r) reductions in barley roots. Furthermore, the water transport activity in intact barley roots was suggested to require phosphorylation that is sensitive to a kinase inhibitor, staurosporine. HvPIP2s also showed water efflux activity in Xenopus oocytes, suggesting a potential ability to mediate water loss from cells under hypertonic conditions. Water transport via HvPIP aquaporins and the significance of reductions of Lp(r) in barley plants during salinity stress are discussed.

In situ separation of root hydraulic redistribution of soil water from liquid and vapor transport

Nocturnal increases in water potential (ψ) and water content (θ) in the upper soil profile are often attributed to root water efflux, a process termed hydraulic redistribution (HR). However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the daily recovery in θ (Δθ), confounding efforts to determine the actual magnitude of HR. We estimated liquid (J(l)) and vapor (J(v)) soil water fluxes and their impacts on quantifying HR in a seasonally dry ponderosa pine (Pinus ponderosa) forest by applying existing datasets of ψ, θ and temperature (T) to soil water transport equations. As soil drying progressed, unsaturated hydraulic conductivity declined rapidly such that J (l) was irrelevant (<2E-05 mm h(-1) at 0-60 cm depths) to total water flux by early August. Vapor flux was estimated to be the highest in upper soil (0-15 cm), driven by large T fluctuations, and confounded the role of HR, if any, in nocturnal θ dynamics. Within the 15-35 cm layer, J(v) contributed up to 40% of hourly increases in nocturnal soil moisture. While both HR and net soil water flux between adjacent layers contribute to θ in the 15-65 cm soil layer, HR was the dominant process and accounted for at least 80% of the daily recovery in θ. The absolute magnitude of HR is not easily quantified, yet total diurnal fluctuations in upper soil water content can be quantified and modeled, and remain highly applicable for establishing the magnitude and temporal dynamics of total ecosystem water flux.

The Effect of Polycarbophil on Water Transport in Rat Intestine

The effect of polycarbophil, polyacrylic acid cross-linked with divinylglycol, on rat intestinal water transport was evaluated by the in-situ loop and in-situ perfusion methods. When polycarbophil was applied in the loop, the net water flux was reduced not only in the jejunum but also in the colon. With the in-situ perfusion technique it was shown that the effect of polycarbophil was to reduce water influx; water efflux was not altered. The action of polycarbophil was not affected by the osmolarity of the perfusate or the site of perfusion. The effect of polycarbophil on net water flux was greater than that of carmellose sodium. The results suggest that polycarbophil could be used to alleviate constipation.

Effect of Cadmium on Water Metabolism Regulation byMeriones shawi(Rodentia, Muridae)

In Tunisia, it was reported that Meriones shawi, a desert rodent, was contaminated by heavy metals around several industrial sites. In the present study, the effects of cadmium (Cd) on water metabolism regulation was studied in adult male Meriones shawi that received contaminated diet with cadmium chloride (CdCl2) for 8 days at (1 g Cd/1 L H2O/1.5 kg of granule flour). Expression of arginine-vasopressin (AVP), a crucial hormone for water regulation, was studied by immunohistochemistry in the hypothalamic supraoptic nucleus and paraventricular nucleus. Inspite of variations in water intake, Meriones shawi successfully maintained a balance between water influx and efflux. Cd treatment did not modify water flux rates. Total body water volume remained constant during the treatment in all groups studied. In contrast to what is known in laboratory rodents, water restriction induced an increase in expression of AVP in both supraoptic nucleus and paraventricular nucleus after eight days and two weeks of the experiment, respectively. A similar effect was also observed by treating Meriones with Cd. However, expression of AVP immunoreactivity from deprived water animals in the presence of Cd was markedly and significantly lower than in the absence of Cd. We conclude that Cd exposure modifies the vasopressinergic neuronal system and provides information regarding the neurotoxicity risks that this element presents for mammals and human populations exposed to even low amounts of Cd, without directly affecting water metabolism. Suitability of Meriones shawi as an accumulation bioindicator for Cd was also confirmed in this study.