Effects Of Hyperosmotic Stress Research Articles

Effects of hyperosmotic stress on the intestinal microbiota, transcriptome, and immune function of mandarin fish (Siniperca chuatsi)

As a specific ecological factor of the aquatic environment, salinity can significantly affect intestinal and intestinal microbial homeostasis, which play essential roles in maintaining host health and antibacterial function. To evaluate the effects of saline-alkali water on host health and immune response, in this study, the effects of hyperosmotic stress on intestinal functions, including the intestinal microecosystem, intestinal immune response-related gene expression and intestinal antioxidant capacity, were investigated in mandarin fish (Siniperca chuatsi) after 45 days of exposure to freshwater (0 ppt salinity) or 3 ppt salinity, 6 ppt salinity, 9 ppt salinity, and 12 ppt salinity water environments. The results revealed that the intestinal microbial community composition could be altered and reshaped by hyperosmotic stress. Notably, the relative abundances of the probiotic bacterium Lactobacillus, the pathogenic bacterium Vibrio, and the metabolism-related bacteria Cetobacterium and Gluconobacter in the 6 ppt salinity group was higher than those in other groups, whereas no significant difference was observed among five groups. The analysis of intestinal transcriptome revealed several differentially expressed genes (DEGs) associated with several immune-related DEGs related to proinflammatory cytokines, anti-inflammatory cytokines, antioxidant defense, antimicrobial effects, and cell apoptosis. According to an analysis of intestinal physiological properties, the activity of alkaline phosphatase (AKP) and acid phosphatase (ACP) was significantly increased by hyperosmotic stress, especially in the 6 ppt salinity group. The present study provides essential insights into the influences of saline-alkali water on the health status and immune functions of mandarin fish; additionally, it provides an important foundation for further studies on the effects of complex relationship between intestinal flora and complex host environment on host disease resistance.

Genetically encoded voltage indicator proteins revealed differential effects of hyperosmotic stress on yeast plasma membrane potential imposed by different stress conditions.

Cells can be affected by several causes of osmotic stress, by which they are forced to adapt. An essential aspect of adaptation is ion regulation, and many insights into such complex processes can be obtained through measurement of the plasma membrane potential (PMP) of cells during stress. We recently established genetically encoded voltage indicator proteins that could be utilized to report the yeast PMP change in real time. In this work, we employed this method to monitor the early change in the PMP of yeast Saccharomyces cerevisiae with intact cell wall, immediately following hyperosmotic up-shock due to various stress agents. The results pointed to differential effects of NaCl, sorbitol and polyethylene glycol (PEG) 6000. Yeast PMP was more responsive toward PEG 6000 than NaCl and sorbitol at comparable osmotic pressure, and PEG 6000 stimulated the largest response magnitude, followed by sorbitol and NaCl, respectively. After prolonged treatment, PEG 6000 also instigated distinct cell morphology from NaCl and sorbitol. Accordingly, this study presents new evidence supporting multiple pathways underlying yeast adaptation to varying hyperosmotic conditions, enabled through the optical physiology approach. Our findings promote better understanding of the yeast cellular response to hyperosmotic stress, with tenable relevance to the physiologically related plant cells.

A Preliminary Study on the Effects of Hyperosmotic Stress on Plasma Levels of Thyroid Hormones in Male Catfish, Clarias gariepinus

Male air-breathing catfish, Clarias gariepinus were exposed to hyperosmolar mannitol solution (250 mM) to determine its effect on the plasma levels of thyroxine (T4) and triiodothyronine (T3) during the winter, spring, summer and autumn seasons. During the winter season, hyperosmolar mannitol solution significantly increased the plasma levels of T4 throughout the duration of exposure, whereas the plasma T3 levels significantly increased only at 12-48 h. During the spring season, significant decreases in the plasma levels of T4 were observed only at 12 and 48 h, and significant increases in the plasma levels of T3 were observed only at 6-24 h. During the summer season, the plasma levels of T4 significantly increased at 6 h and decreased at 24-48 h, while the plasma levels of T3 significantly increased only at 6 and 24 h. During the autumn season, the plasma levels of T4 significantly increased at 6, 12 and 48 h and the plasma levels of T3 significantly decreased at 6, 24 and 48 h. These results indicate the season-dependent and differential effects of the hyperosmolar mannitol solution on the plasma levels of thyroid hormones in Clarias gariepinus.

Effect of hyperosmotic stress on proliferation and apoptosis of hepatocellular carcinoma Huh7 cells

Objective To investigate the effect of hyperosmotic stress on the proliferation and apoptosis of hepatocellular carcinoma Huh7 cells,and preliminarily explore the mechanism.Methods The expression of mammalian osmotic regulator nuclear factor of activated T-cells 5 (NFAT5) was detected in 64 cases of hepatocellular carcinoma by using immunohistochemistry.NaC1 was used as a chemical hyperosmotic-inducible reagent to mimic tumor hyperosmotic microenvironment.The expression of NFAT5 protein was analyzed by Western blotting.Cell apoptosis was examined by using flow cytometry and cell growth was measured by methyl-thiazol-tetrazolium (MTT) assay.Results NFAT5 positive expression rate was low (9.38％) in hepatocellular carcinoma tissue but high in the corresponding peritumoral tissue (68.75％) (P ＜0.01).Under hyperosmotic stress (100 mmol/L NaC1) for 24 h,the protein expression levels of NFAT5 in Huh7 cells were up-regulated (P ＜ 0.01).The apoptosis rate in experimental group [(26.0 ± 3.2) ％] was significantly higher than that in blank control group [(0.8 ± 0.2) ％] (P ＜0.01).Hyperosmotic stress (100 mmol/L NaCl) also inhibited growth of Huh7 cells with the cell growth inhibitory rate being (31.35 ± 2.09) ％ (P ＜ 0.01).Conclusion There are obvious differences in the expression of the only mammalian osmotic regulator NFAT5 between hepatocellular carcinoma tissue and peritumoral tissue.Hyperosmotic stress can up-regulate the NFAT5 protein expression,induce apoptosis of hepatocellular carcinoma Huh7 cells,and inhibit cells proliferation. Key words: Carcinoma, hepatocellular; Hyperosmotic stress; Apoptosis; Proliferation

Hypertonic stress regulates amino acid transport and cell cycle proteins in chick embryo hepatocytes

Hyperosmotic stress affects cell growth, decreasing cell volume and increasing the uptake of organic osmolytes. However, the sensitivity of embryonic cells to osmotic treatment remains to be established. We have analysed some aspects of cell-cycle control and amino-acid transport in hypertonic conditions during prenatal life. The effects of hyperosmotic stress on amino-acid uptake mediated by system A, (3)H-thymidine incorporation, and regulation of cell-cycle proteins were analysed in chick embryo hepatocytes. Hypertonic stress increased system A activity and caused cell-cycle delay. Effects on amino-acid transport involved p38 kinase activation and new carrier synthesis. Cyclin D1, cdk4 (cyclin-dependent kinase 4) and PCNA (proliferating-cell nuclear antigen) levels decreased, whereas cyclin E, p21 and p53 levels were unchanged. Incorporation of (3)H-leucine indicated decreased synthesis of cyclin D1. In contrast, analysis of mRNA by qRT-PCR (quantitative real-time PCR) showed a net increase of cyclin D1 transcripts, suggesting post-transcriptional regulation. The data show that chick embryo hepatocytes respond to hyperosmotic conditions by arresting cell growth to prevent DNA damage and increasing osmolyte uptake to regulate cell volume, indicating that the adaptive response to environmental stress exists during prenatal life.

Decrease of prestin expression by increased potassium concentration in organotypic cultures of the organ of Corti of newborn rats

Prestin is the motor protein of the outer hair cells of the organ of Corti and a key factor in ensuring a high sensitivity level of mammalian hearing. In the present study, we examined the effects of increased extracellular potassium (K +) concentration on the expression of prestin mRNA and the transcription factors Gata-3 and Carf in the organotypic culture of the organ of Corti of newborn rats. Mannitol and NaCl were used to analyze possible effects of hyperosmotic stress or ion-specific changes, respectively. An increase in prestin expression by a factor of 1.5–2.0 was seen in cultures grown in the presence of 5 mM K +. Potassium concentration of 35 and 55 mM induced a parallel decrease in prestin and Carf expression, but Gata-3 expression increased. Mannitol had no effect on gene expression whereas increased NaCl concentrations decreased prestin, but not Carf expression. The data suggest that chronic depolarization might decrease the prestin expression and possibly contribute to hearing loss and tinnitus.

Effects of Osmotic Stress on Rhamnolipid Synthesis and Time-Course Production of Cell-To-Cell Signal Molecules by Pseudomonas aeruginosa

Biosynthesis of biosurfactant rhamnolipids by Pseudomonas aeruginosa depends on two hierarchical quorum sensing systems, LasRI and RhlRI, which synthesize and sense the signal molecules N-(3-oxododecanoyl)-L-homoserine lactone (3OC12-HSL) and N-butyryl-L-homoserine lactone (C4-HSL), respectively. The Pseudomonas Quinolone Signal (PQS) is a third cell-to-cell signal molecule connecting these two systems, and its precursor, 2-heptyl-4-quinolone (HHQ), also constitutes a signal. The chronology of the production of signal molecules and rhamnolipids was determined during growth in PPGAS medium. Hyperosmotic condition (0.5 M NaCl) moderately affected growth, and led to intra-cellular accumulation of compatible solutes. Production of signal molecules was delayed and their highest concentrations were 2.5 to 5 fold lower than in NaCl-free PPGAS, except for HHQ, the highest concentration of which was increased. The presence of NaCl prevented rhamnolipid synthesis. When the osmoprotectant glycine betaine was added to PPGAS/NaCl medium, it was imported by the cells without being metabolized. This did not improve growth, but reestablished the time-courses of HSL and HHQ accumulation and fully or partially restored the HSL and PQS levels. It also partially restored rhamnolipid production. Quantification of mRNAs encoding enzymes involved in HSL, PQS, and rhamnolipid biosyntheses confirmed the effect of hyperosmotic stress and glycine betaine at the gene expression level.

Effect of Hyperosmotic Stress on the Gene Expression and Activity of Neuronal Nitric Oxide Synthase (nNOS) in the Preoptic-Hypothalamic Neurosecretory System of the Euryhaline FishOreochromis mossambicus

We examined the effects of hyperosmotic stress on the gene expression and activity of neuronal nitric oxide synthase (nNOS) in the preoptic/hypothalamic neurosecretory system of the euryhaline tilapia Oreochromis mossambicus (Mozambique tilapia) by means of semiquantitative RT-PCR and NADPHd histochemistry. Expression of nos1 was rapidly and transiently up-regulated in the preoptic region and hypothalamus in response to a salinity change (70% seawater, SW). Expression levels increased 4 h after the salinity change and then returned to basal levels within 8 h of the hyperosmotic challenge. NADPHd histochemistry revealed that positive magnocellular and gigantocellular preoptic neurons increased in number 4 h after the salinity change, while the number of parvocellular preoptic neurons reactive for NADPHd showed no significant change. These results indicate that the nNOS gene expression and NOS activity are stimulated in the preoptic/ hypothalamic neurosecretory system in response to hyperosmotic stress and suggest that NO influences neuronal responses to short-term osmotic stimulation in euryhaline fish.

Effects of hyperosmotic stress on cultured airway epithelial cells

Inhalation of hyperosmotic solutions (salt, mannitol) has been used in the treatment of patients with cystic fibrosis or asthma, but the mechanism behind the effect of hyperosmotic solutions is unclear. The relation between osmolarity and permeability changes was examined in an airway cell line by the addition of NaCl, NaBr, LiCl, mannitol, or xylitol (295-700 mOsm). Transepithelial resistance was measured as an indicator of the tightness of the cultures. Cell-cell contacts and morphology were investigated by immunofluorescence and by transmission electron microscopy, with lanthanum nitrate added to the luminal side of the epithelium to investigate tight junction permeability. The electrolyte solutions caused a significant decrease in transepithelial resistance from 450 mOsm upwards, when the hyperosmolar exposure was gradually increased from 295 to 700 mOsm; whereas the nonelectrolyte solutions caused a decrease in transepithelial resistance from 700 mOsm upwards. Old cultures reacted in a more rigid way compared to young cultures. Immuno-fluorescence pictures showed weaker staining for the proteins ZO-1, claudin-4, and plakoglobin in treated samples compared to the control. The ultrastructure revealed an increased number of open tight junctions as well as a disturbed morphology with increasing osmolarity, and electrolyte solutions opened a larger proportion of tight junctions than nonelectrolyte solutions. This study shows that hyperosmotic solutions cause the opening of tight junctions, which may increase the permeability of the paracellular pathway and result in increased transepithelial water transport.

Nicotiana tabacum Osmotic Stress-activated Kinase Is Regulated by Phosphorylation on Ser-154 and Ser-158 in the Kinase Activation Loop

NtOSAK (Nicotiana tabacum osmotic stress-activated protein kinase), a member of the SnRK2 subfamily, is activated rapidly in response to hyperosmotic stress. Our previous results as well as data presented by others indicate that phosphorylation is involved in activation of SnRK2 kinases. Here, we have mapped the regulatory phosphorylation sites of NtOSAK by mass spectrometry with collision-induced peptide fragmentation. We show that active NtOSAK, isolated from NaCl-treated tobacco BY-2 cells, is phosphorylated on Ser-154 and Ser-158 in the kinase activation loop. Prediction of the NtOSAK three-dimensional structure indicates that phosphorylation of Ser-154 and Ser-158 triggers changes in enzyme conformation resulting in its activation. The involvement of Ser-154 and Ser-158 phosphorylation in regulation of NtOSAK activity was confirmed by site-directed mutagenesis of NtOSAK expressed in bacteria and in maize protoplasts. Our data reveal that phosphorylation of Ser-158 is essential for NtOSAK activation, whereas phosphorylation of Ser-154 most probably facilitates Ser-158 phosphorylation. The time course of NtOSAK phosphorylation on Ser-154 and Ser-158 in BY-2 cells subjected to osmotic stress correlates with NtOSAK activity, indicating that NtOSAK is regulated by reversible phosphorylation of these residues in vivo. Importantly, Ser-154 and Ser-158 are conserved in all SnRK2 subfamily members, suggesting that phosphorylation at these sites may be a general mechanism for SnRK2 activation.

Mucin Characteristics of Human Corneal-Limbal Epithelial Cells that Exclude the Rose Bengal Anionic Dye

Rose bengal is an organic anionic dye used to assess damage of the ocular surface epithelium in ocular surface disease. It has been proposed that mucins have a protective role, preventing rose bengal staining of normal ocular surface epithelial cells. The current study was undertaken to evaluate rose bengal staining in a human corneal-limbal epithelial (HCLE) cell line known to produce and glycosylate membrane-associated mucins. HCLE cells were grown to confluence in serum-free medium and switched to DMEM/F12 with 10% serum to promote differentiation. Immunolocalization of the membrane-associated mucins MUC1 and MUC16 and the T-antigen carbohydrate epitope was performed with the monoclonal antibodies HMFG-2 and OC125 and jacalin lectin, respectively. To assess dye uptake, cultures were incubated for 5 minutes with 0.1% rose bengal and photographed. To determine whether exclusion of negatively charged rose bengal requires a negative charge at the cell surface, cells were incubated with fluoresceinated cationized ferritin. The effect of hyperosmotic stress on rose bengal staining in vitro was evaluated by increasing the ion concentration (Ca+2 and Mg+2) in the rose bengal uptake assay. The cytoplasm and nucleus of confluent HCLE cells cultured in media without serum, lacking the expression of MUC16 but not MUC1, as well as human corneal fibroblasts, which do not express mucins, stained with rose bengal. Culture of HCLE cells in medium containing serum resulted in the formation of islands of stratified cells that excluded rose bengal. Apical cells of the stratified islands produced MUC16 and the T-antigen carbohydrate epitope on their apical surfaces. Colocalization experiments demonstrated that fluoresceinated cationized ferritin did not bind to these stratified cells, indicating that rose bengal is excluded from cells that lack negative charges. Increasing the amounts of divalent cations in the media reduced the cellular area protected against rose bengal uptake. These results indicate that stratification and differentiation of corneal epithelial cells, as measured by the capacity to produce the membrane-associated mucin MUC16 and the mucin-associated T-antigen carbohydrate on their apical surfaces provide protection against rose bengal penetrance in vitro and suggest a role for membrane-associated mucins and their oligosaccharides in the protection of ocular surface epithelia.

Effect of osmotic stress on the derepression of invertase synthesis in nonconventional yeasts

The aim of this study was to analyse the effect of osmotic stress on the biosynthesis of invertase enzyme in nonconventional yeasts. Invertase activities of the nonconventional yeast species belonging to Kluyveromyces, Schwanniomyces and Pichia genus were measured either in the presence or in the absence of various amounts of NaCl. The effect of hyperosmotic stress on the glucose consumption of Saccharomyces cerevisiae and Pichia anomala were also compared. Like S. cerevisiae, derepression of invertase synthesis in Kluyveromyces lactis, Schwanniomyces occidentalis and Pichia jadinii is inhibited by hyperosmotic stress. However, derepression of invertase synthesis in P. anomala is not affected by hyperosmotic stress. In addition, low levels of osmotic stress activated invertase synthesis three- to fourfold in P. anomala and K. lactis. This study shows that low levels of osmotic stress induces the invertase synthesis at very high levels in P. anomala and K. lactis. Glucose consumption was not influenced at significant levels by the hyperosmotic stress in P. anomala. This study shows the activation of invertase synthesis by low levels of osmotic stress in P. anomala and K. lactis.

37 Effects of hyperosmotic stress on cultured airway epithelial cells

37 Effects of hyperosmotic stress on cultured airway epithelial cells

Roles of the Mitochondria and Endoplasmic Reticulum in Calcium Elevation during Osmotic Shock in Adrenocortical Cells

Steroid hormones participate in various metabolic processes, and dysfunction of the adrenocortical system leads to numerous pathologies in humans. One of the factors that can influence the secretory properties of adrenocorticocytes is changes in the cell volume observed during osmotic shock. In our study, we tested the hypothesis that osmotic stress modifies intracellular Ca2+ signalling and in such a way can influence the secretion of steroids by adrenocorticocytes. The effects of hyperosmotic stress on the cytosolic Ca2+ concentration ([Ca]i) in cultured adrenocortical cells from the zona fasciculata of the rat adrenals were investigated using the indicator fura-2 technique. Our experiments have shown that exposure of the cells to a hyperosmotic solution caused a decrease in the cell volume, as well as a reversible rise in the [Ca]i. Calcium-free media partly eliminated [Ca]i responses. Pretreatment of the cells with thapsigargin or CCCP (blockers of internal calcium stores) significantly decreased the magnitude of responses induced by osmotic stress. These findings indicate that osmotic shock causes an increase in the [Ca]i in adrenocortical cells, mostly due to depletion of the intracellular stores, and may in such a way stimulate steroidogenesis.

Inositol (1,4,5)-trisphosphate: first in the hyperosmotic stress response?

Salt and drought stresses constitute widespread challenges faced by plants in natural ecosystems as well as in agriculture. Normally, plants respond and adapt to stress by making physiological, developmental and biochemical changes. The development or appearance of tolerance to stress triggers a complex set of cellular interactions that ultimately result in altered expression patterns of numerous genes involved in the adaptive response. Although there have been few studies concerning the early events that induce adaptive processes, two responses have been defined: rapid changes in cytosolic free Ca2+ concentration and rapid rises in cellular levels of inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] 1. Although it is known that the induction of gene-encoding enzymes of the plant phosphoinositide cycle can be triggered by hyperosmotic stress, little detailed information is currently available about the immediate effects of hyperosmotic stress on phosphoinositide-metabolizing enzymes and Ins(1,4,5)P3 generation.

P-143 - Effect of Hyperosmotic stress on expression of aldose reductase gene in cultured rat Schwann cells

P-143 - Effect of Hyperosmotic stress on expression of aldose reductase gene in cultured rat Schwann cells

The heat-shock transcription factor HSF1 is rapidly activated by either hyper- or hypo-osmotic stress in mammalian cells.

Osmoregulation, the cellular response to environmental changes of osmolarity and ionic strength, is important for the survival of living organisms. We have demonstrated previously that an exposure of mammalian cells to hypo-osmotic stress, either in growth medium (30% growth medium and 70% water) or in binary solution containing sorbitol and water, prominently induced the DNA-binding activity of the heat-shock transcription factor (HSF1) [Huang, Caruccio, Liu and Chen (1995) Biochem. J. 307, 347-352]. Since hyperosmotic and hypo-osmotic stress usually elicit opposite biological responses, we wondered what would be the effect of hyperosmotic stress on HSF activation. In this study we have examined the HSF DNA-binding activity in HeLa cells maintained in the sorbitol/water binary solution over a wide concentration range (0.1-0.9 M) and in Dulbecco's medium supplemented with sorbitol or NaCl. We found that HSF-binding activity could be induced prominently under both hypo-osmotic (0.1-0.25 M) and hyperosmotic conditions (0.50-0.90 M). In both cases, HSF activation was observed within 5 min after changing the osmotic pressure. The activation was accompanied by both HSF trimerization and nuclear translocation, and appeared to be independent of protein synthesis. The effects of hypo- or hyper-osmotic stress on HSF activation could be reversed once the cells were returned to iso-osmotic conditions (0.30M) with a half-life (t12) of 25 min or less. This rapid turnover of the osmotic-stress-induced HSF-binding activity was inhibited by cycloheximide, a potent inhibitor of protein synthesis. Unlike heat shock, activation of HSF by either hypo- or hyper-osmotic stress did not lead to an accumulation of heat-shock protein 70 (HSP70) mRNA in HeLa cells. We propose that HSF activation during osmotic stress may serve physiological functions independent of the synthesis of heat-shock proteins.

Enhancement of monoclonal antibody production by immobilized hybridoma cell culture with hyperosmolar medium

To determine the effect of hyperosmotic stress on the monoclonal antibody (MAb) production by calcium-alginate-immobilized S3H5/gamma2bA2 hybridoma cells, the osmolalities of medium in the MAb production stage were varied through the addition of NaCI. The specific MAb productivity (q(MAb)) of immobilized cells exposed to abrupt hyperosmotic stress (398 mOsm/kg) was increased by 55% when compared with that of immobilized cells in the control culture (286 mOsm/kg). Furthermore, this enhancement of q(MAb) was not transient. Abrupt increase in osmolality, however, inhibited cell growth, resulting in no increase in volumetric MAb productivity (r(MAb)). On the other hand, gradual increase in osmolality allowed further cell growth while maintaining the enhanced q(MAb) immobilized cells. The q(MAb) immobilized cells at 395 mOsm/kg was 0.661 +/- 0.019 mug/10(6) cells/h, which is almost identical to that of immobilized cells exposed to abrupt osmotic stress. Accordingly, the r(MAb) was increased by ca. 40% when compared with that in the control immobilized cell culture. This enhancement in i(MAb) of immobilized S3H5/gamma2bA2 hybridoma cells by applying gradual osmotic stress suggests the potential of using hyperosmolar medium in other perfusion culture systems for improved MAb production. (c) 1995 John Wiley & Sons, Inc.

Hyperosmotic modulation of the cytosolic calcium concentration in a rat osteoblast-like cell line.

1. The effects of hyperosmotic stress on cytosolic calcium concentration ([Ca2+]i) were studied by ratio image analysis in single cells of an osteoblast-like bone cell line (RCJ 1.20) loaded with fura-2 AM. 2. The ratio (340 nm/380 nm) of steady-state [Ca2+]i in resting osteoblasts kept in Hepes-buffered medium was 0.82 +/- 0.04. A hyperosmotic stimulus (200 mosmol l-1 sucrose) produced a [Ca2+]i transient with a peak ratio of 1.28 +/- 0.09, which decayed with an apparent half-life (t1/2) of 42.7 +/- 2.6 s. 3. The hyperosmotically induced [Ca2+]i transients were insensitive to verapamil, diltiazem or nifedipine, which excludes the involvement of dihydropyridine-sensitive Ca2+ channels in the process. Non-specific Ca2+ channel blockers (Mn2+, Ni2+, La3+ or Gd3+) partially abolished the hyperosmotically induced [Ca2+]i elevation, indicating the contribution of extracellular Ca2+ influx. 4. A hyperosmotic stimulus applied in Ca(2+)-free medium (0.5 mM EGTA) lowered the [Ca2+]i peak to a ratio of 0.96 +/- 0.08 (P < 0.001) compared with a Ca(2+)-containing medium. This suggests that the [Ca2+]i increase is due to extracellular influx, as well as release from an intracellular Ca2+ pool. 5. Application of thapsigargin (0.5 microM), a specific inhibitor of endoplasmic reticulum Ca(2+)-ATPase, in Ca(2+)-free medium caused transient [Ca2+]i elevation to peak ratios of 1.33 +/- 0.09, and completely abolished the [Ca2+]i response to a hyperosmotic stimulus. This implies the existence of a thapsigargin-sensitive intracellular pool of Ca2+ that is mobilized by hyperosmotic stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

The Effect of Hyperosmotic Stress on Tongue Extension in the Western Toad, Bufo boreas

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