Effects of hypoxia induced by Na2S2O4 on intracellular calcium and resting potential of mouse glomus cells

Comparison of hypoxic effects induced by chemical and physical hypoxia on cardiomyocytes

The degree and duration of chemical hypoxia induced by sodium dithionite (Na₂S₂O₄) have not been reported. It is not yet clear how much reduction in the O₂ concentration (physical hypoxia) can lead to hypoxia in cultured cardiomyocytes. In this study, oxygen microelectrodes were used to measure changes in the O₂ concentration in media containing different concentrations of Na₂S₂O₄. Then, hypoxic effects of 0.8, 1.0, and 2.0 mM Na₂S₂O₄ or 1%, 3%, and 5% O₂ in cultured cardiomyocytes from neonatal rats were observed and compared. The results showed that the O₂ concentration failed to remain constant by Na₂S₂O₄ treatment during the 180-minute observation period. Only the 2.0 mM Na₂S₂O₄ group significantly increased the expression of hypoxia-inducible factor 1α (HIF-1α) and hypoxic responses. Notably, 3% O₂ only significantly increased the expression of HIF-1α in cardiomyocytes, while 1% O₂ not only increased the expression of HIF-1α but also increased the apoptotic rate in cardiomyocytes. These results suggest that Na₂S₂O₄ is not suitable for establishing a hypoxic model in cultured neonatal rat cardiomyocytes, and neonatal rat cardiomyocytes cultured at or below 1% O₂ induced significant hypoxic effects, which can be used as a starting O₂ concentration for establishing a hypoxic cell model.

Trichosanthis Pericarpium Aqueous Extract Protects H9c2 Cardiomyocytes from Hypoxia/Reoxygenation Injury by Regulating PI3K/Akt/NO Pathway

Trichosanthis Pericarpium (TP) is a traditional Chinese medicine for treating cardiovascular diseases. In this study, we investigated the effects of TP aqueous extract (TPAE) on hypoxia/reoxygenation (H/R) induced injury in H9c2 cardiomyocytes and explored the underlying mechanisms. H9c2 cells were cultured under the hypoxia condition induced by sodium hydrosulfite for 30 min and reoxygenated for 4 h. Cell viability was measured by MTT assay. The amounts of LDH, NO, eNOS, and iNOS were tested by ELISA kits. Apoptotic rate was detected by Annexin V-FITC/PI staining. QRT-PCR was performed to analyze the relative mRNA expression of Akt, Bcl-2, Bax, eNOS, and iNOS. Western blotting was used to detect the expression of key members in the PI3K/Akt pathway. Results showed that the pretreatment of TPAE remarkably enhanced cell viability and decreased apoptosis induced by H/R. Moreover, TPAE decreased the release of LDH and expression of iNOS. In addition, TPAE increased NO production and Bcl-2/Bax ratio. Furthermore, the mRNA and protein expression of p-Akt and eNOS were activated by TPAE pretreatment. On the contrary, a specific inhibitor of PI3K, LY294002 not only inhibited TPAE-induced p-Akt/eNOS upregulation but alleviated its anti-apoptotic effects. In conclusion, results indicated that TPAE protected against H/R injury in cardiomyocytes, which consequently activated the PI3K/Akt/NO signaling pathway.

Shexiang Tongxin Dropping Pill () Protects against Na2S2O4-Induced Hypoxia-Reoxygenation Injury in H9c2 Cells

OBJECTIVES

To investigate the protective effects of Shexiang Tongxin Dropping Pill (, STP) on Na₂S₂O₄-induced hypoxia-reoxygenation injury in cardiomyoblast H9c2 cells.

METHODS

The cell viability and levels of mRNA and protein expression in H9c2 cells were determined following Na₂S₂O₄-induced hypoxia using Hoechst staining, annexin V/propidium iodide (PI) flow cytometry, real-time polymerase chain reaction and Western blot analysis.

RESULTS

STP pretreatment significantly increased the viability and inhibited aberrant morphological changes in H9c2 cardiomyoblast cells induced by Na₂S₂O₄ treatment (P<0.05). In addition, STP pretreatment attenuated Na₂S₂O₄-induced hypoxic damage, down-regulated the expression of pro-apoptotic Bax, and up-regulated the expression of anti-apoptotic Bcl-2 in H9c2 cells (P<0.05).

CONCLUSIONS

STP was strongly cardioprotective in hypoxia-reoxygenation injury by preventing hypoxic damage and inhibiting cellular apoptosis. These results further support the use of STP as an effective drug for the treatment of ischemic heart disease.

Dimethyl Sulfoxide (DMSO) Decreases Cell Proliferation and TNF-α, IFN-γ, and IL-2 Cytokines Production in Cultures of Peripheral Blood Lymphocytes

Dimethylsulfoxide (DMSO) is an amphipathic molecule composed of a polar domain characterized by the sulfinyl and two nonpolar methyl groups, for this reason it is able to solubilize polar and nonpolar substances and transpose hydrophobic barriers. DMSO is widely used to solubilize drugs of therapeutic applications and studies indicated that 10% v/v concentration did not modify culture viability when used to treat human peripheral blood mononuclear cells (PBMC). However, some DMSO concentrations could influence lymphocyte activation and present anti-inflammatory effects. Therefore, the objective of this study was to evaluate the effect of DMSO on lymphocyte activation parameters. Cell viability analysis, proliferation, and cytokine production were performed on PBMC from six healthy subjects by flow cytometry. The results indicated that 2.5% v/v DMSO concentrations did not modify lymphocytes viability. DMSO at 1% and 2% v/v concentrations reduced the relative proliferation index of lymphocytes and at 5% and 10% v/v concentrations reduced the percentage of total lymphocytes, cluster of differentiation 4⁺ (CD4⁺) T lymphocytes and CD8⁺ T lymphocytes interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α) and interleukin-2 (IL-2) producers. Thus, it was concluded that DMSO has an in vitro anti-inflammatory effect by reducing lymphocyte activation demonstrated with proliferation reduction and the decrease of cytokine production.

Genistein inhibition of OGD-induced brain neuron death correlates with its modulation of apoptosis, voltage-gated potassium and sodium currents and glutamate signal pathway

In the present study, we established an in vitro model of hypoxic-ischemia via exposing primary neurons of newborn rats to oxygen-glucose deprivation (OGD) and observing the effects of genistein, a soybean isoflavone, on hypoxic-ischemic neuron viability, apoptosis, voltage-activated potassium (Kv) and sodium (Nav) currents, and glutamate receptor subunits. The results indicated that OGD exposure reduced the viability and increased the apoptosis of brain neurons. Meanwhile, OGD exposure caused changes in the current-voltage curves and current amplitude values of voltage-activated potassium and sodium currents; OGD exposure also decreased GluR2 expression and increased NR2 expression. However, genistein at least partially reversed the effects caused by OGD. The results suggest that hypoxic-ischemia-caused neuronal apoptosis/death is related to an increase in K(+) efflux, a decrease in Na(+) influx, a down-regulation of GluR2, and an up-regulation of NR2. Genistein may exert some neuroprotective effects via the modulation of Kv and Nav currents and the glutamate signal pathway, mediated by GluR2 and NR2.

Neuroprotective effects of gallic acid against hypoxia/reoxygenation-induced mitochondrial dysfunctions in vitro and cerebral ischemia/reperfusion injury in vivo

Oxidative stress and mitochondrial dysfunction are frequently implicated in the pathology of secondary neuronal damage following cerebral ischemia/reperfusion. Recent evidence suggests that gallic acid (GA) reverses oxidative stress in rat model of streptozotocin-induced dementia, but the roles and mechanisms of GA on cerebral ischemia/reperfusion injury remain unknown. Here we investigated the potential roles and mechanisms of GA in hypoxia/reoxygenation induced by sodium hydrosulfite (Na2S2O4) in vitro and cerebral ischemia/reperfusion induced by middle cerebral artery occlusion (MCAO) in vivo. 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, 5, 5', 6, 6'-tetrachloro-1, 1', 3, 3'-tetraethylbenzimidazol carbocyanine iodide (JC-1), Dichlorofluorescin diacetate (DCF-DA) and MitoSOX fluorescent assay, Clark-type oxygen electrode, firefly luciferase assay, and calcium-induced mitochondrial swelling were conducted to detect cell death, mitochondrial membrane potential (MMP), intracellular and mitochondrial reactive oxygen species (ROS), oxygen consumption, ATP level, and mitochondrial permeability transition pore (MPTP) viability. We firstly find that modulation of the mitochondrial dysfunction is an important mechanism by GA attenuating hypoxia/reoxygenation insult. To further assess the effects of GA on cerebral ischemia/reperfusion injury, 2, 3, 5-triphenyl-tetrazolium chloride (TTC) staining, dUTP nick-end labeling (TUNEL) assay, and Cytochrome C (Cyt C) release were performed in MCAO rats. The results support that GA is useful against cerebral ischemia/reperfusion injury as a potential protective agent.

Carotid chemoreceptor "resetting" revisited

Carotid body (CB) chemoreceptors transduce low arterial O(2) tension into increased action potential activity on the carotid sinus nerves, which contributes to resting ventilatory drive, increased ventilatory drive in response to hypoxia, arousal responses to hypoxia during sleep, upper airway muscle activity, blood pressure control and sympathetic tone. Their sensitivity to O(2) is low in the newborn and increases during the days or weeks after birth to reach adult levels. This postnatal functional maturation of the CB O(2) response has been termed "resetting" and it occurs in every mammalian species studied to date. The O(2) environment appears to play a key role; the fetus develops in a low O(2) environment throughout gestation and initiation of CB "resetting" after birth is modulated by the large increase in arterial oxygen tension occurring at birth. Although numerous studies have reported age-related changes in various components of the O(2) transduction cascade, how the O(2) environment shapes normal CB prenatal development and postnatal "resetting" remains unknown. Viewing CB "resetting" as environment-driven (developmental) phenotypic plasticity raises important mechanistic questions that have received little attention. This review examines what is known (and not known) about mechanisms of CB functional maturation, with a focus on the role of the O(2) environment.

Quercetin protects oligodendrocyte precursor cells from oxygen/glucose deprivation injury in vitro via the activation of the PI3K/Akt signaling pathway

The aim of this study was to investigate the protection of quercetin (QUE) on oligodendrocyte precursor cells (OPCs) from oxygen/glucose deprivation (OGD)-induced injury in vitro and explore whether the PI3K/Akt signaling pathway contributed to the protection provided by quercetin. The OGD condition was induced by including 2mM sodium dithionite (Na(2)S(2)O(4)) in glucose-free DMEM medium. The concentration of QUE in this study ranged from 3μM to 81μM. OPCs were identified by immunocytochemical staining. Cell viability was analyzed using the water soluble tetrazolium salt-8 (WST-8) and lactate dehydrogenase assay (LDH). The morphological changes of the nucleus were measured using Hoechst 33258 nuclear staining, and the ratio of apoptotic cells was determined by FITC annexin V- and propidium iodide (PI) flow cytometry assay kit. In addition, the levels of pro-apoptotic proteins such as cleaved-caspase-3 and Bax and the anti-apoptotic proteins p-Akt and Bcl-2 were quantified using western blotting. The results showed that the OPC cell survival rate was significantly increased by incubation in conditioned medium supplemented with QUE as measured by the WST-8 assay, while the LDH release rate was significantly decreased as analyzed by the LDH assay. Furthermore, apoptosis assay showed that the apoptosis ratio of OPCs was also dramatically reduced by QUE. Western blotting showed that the expression levels of Bax and cleaved-caspase-3 proteins were down-regulated, while Bcl-2 and p-Akt were up-regulated. Further study showed that the increase in p-Akt by QUE was reduced by the PI3K inhibitor LY294002. These results indicated that QUE effectively protected OPCs from OGD-induced injury and that the mechanism might be related to the activation of the PI3K/Akt signaling pathway.

Pharmacological protection of hearing loss in the mouse model of endolymphatic hydrops

OBJECTIVES/HYPOTHESIS

Excitotoxic and related inflammatory injury are implicated in the spiral ganglion degeneration seen with Meniere's disease and endolymphatic hydrops (ELH). Excitotoxicity is initiated with glutamate elevation and associated with downstream increases in reactive oxygen species resulting in inflammation-mediated neuronal degeneration. This study tests the hypothesis that interruption of the initial and/or downstream aspects of excitotoxicity should provide hearing protection in ELH-associated hearing loss.

STUDY DESIGN

This study tests whether riluzole, a glutamate release inhibitor, and dimethylsulfoxide (DMSO), an anti-inflammatory and antioxidant solvent with favorable properties at the level of glutamate receptors, can protect against early-stage hearing loss in a mouse model of ELH.

METHODS

The Phex(Hyp-Duk) mouse spontaneously develops ELH and postnatal hearing loss. Starting at postnatal day 6 (P6), daily injections of riluzole + DMSO or just DMSO were administered. Untreated mutants served as controls. At P21, P25, and P30, hearing function was assessed by recording auditory brainstem responses. A cochlear function index was developed to assess global cochlear function at each time point.

RESULTS

Compared to no treatment, DMSO provided significant hearing protection (P < .05). The riluzole + DMSO also showed protection, but it was statistically indistinguishable from DMSO alone; a synergistic increase in protection with riluzole was not observed.

CONCLUSIONS

This study demonstrates pharmacological hearing protection in an animal model of ELH. The results support the assertion that inflammatory (reactive oxygen species) injury, which is part of the excitotoxic pathway, contributes to the development of ELH-associated hearing loss.

Dimethyl sulfoxide (DMSO) exposure to human peripheral blood mononuclear cells (PBMCs) abolish T cell responses only in high concentrations and following coincubation for more than two hours

Immunotherapies based on reinfusion of autologous cells incubated ex vivo with peptides reconstituted in toxic solvents, such as DMSO, are now performed on a routine basis. However, the toxic effects of the most common solvent used, DMSO, on T cell responses from human PBMCs, have not previously been evaluated in detail. Here, in preparation for a first-in-man human phase I vaccine trial comprising reinfusion of autologous HIV peptide-pulsed PBMCs, human PBMCs from healthy and HIV-infected donors were exposed in vitro to a range of DMSO concentrations, and for a range of time periods. Polychromatic flow cytometry was used to evaluate the influence of DMSO on functional T cell responses. We report that high concentrations of up to 10% of DMSO for 1 hour do not affect the cell viability, the magnitude or the functional profile of CD4(+) and CD8(+) T cell responses, regardless of antigen specificity and HLA class I restriction. In contrast, >2% for >2 hours compromises these responses. These data are relevant in the design of immunotherapies based on pulsing a large number of peptides onto antigen presenting cells prior to reinfusion.

Cytotoxic effects of dimethyl sulphoxide (DMSO) on cochlear organotypic cultures

The amphipathic molecule dimethyl sulphoxide (DMSO) is a solvent often used to dissolve compounds applied to the inner ear; however, little is known about its potential cytotoxic side effects. To address this question, we applied 0.1-6% DMSO for 24h to cochlear organotypic cultures from postnatal day 3 rats and examined its cytotoxic effects. DMSO concentrations of 0.1% and 0.25% caused little or no damage. However, concentrations between 0.5% and 6% resulted in stereocilia damage, hair cell swelling and a dose-dependent loss of hair cells. Hair cell damage began in the basal turn of the cochlea and spread towards the apex with increasing concentration. Surprisingly, DMSO-induced damage was greater for inner hair cells than outer hair cell whereas nearby supporting cells were largely unaffected. Most hair cell death was associated with nuclear shrinkage and fragmentation, morphological features consistent with apoptosis. DMSO treatment induced TUNEL-positive staining in many hair cells and activated both initiator caspase-9 and caspase-8 and executioner caspase-3; this suggests that apoptosis is initiated by both intrinsic mitochondrial and extrinsic membrane cell death signaling pathways.

Promoter polymorphisms which modulate APP expression may increase susceptibility to Alzheimer's disease

Increasing evidence indicates that variants in promoter of the beta-amyloid precursor protein (APP) gene could up-regulate the APP gene expression and aggravate the amyloid beta protein (A beta) accumulation, thus contributing to the development of Alzheimer's disease (AD). In Chinese Han populations we found three polymorphisms in APP promoter: -877T/C(rs466433), -955A/G(rs364048) and -9G/C. The -877T and -955A alleles were over-represented in 209 sporadic AD (SAD) patients when compared to those in 437 healthy individuals. Furthermore, -877T/C and -955A/G were in strong linkage disequilibrium and they constructed a relatively risky -877T/-955A and a relatively protective -877C/-955G. Luciferase reporter assay indicated -877T/-955A had four times higher transcriptional activity than -877C/-955G. A more marked increase in -877T/-955A transcriptional activity was seen when under A beta(25-35) treatment. As for the -9G/C polymorphism, significant differences between the two alleles were not observed either in genetic evaluation or in functional assay. The present study provides strong evidence that APP promoter polymorphisms that significantly increase APP expression levels are associated with development of SAD.

Calcium channels of cultured rat glomus cells in normoxia and acute hypoxia

Glomus cells harvested from Wistar rat carotid bodies were cultured for 4 to 7 days. Inward calcium currents elicited by voltage ramps (0.24 V/s) or pulses were recorded during voltage-clamping in the whole-cell and perforated patch configurations. Currents were enhanced by an excess of [Ca(2+)](o), barium and BayK 8644, and depressed or eliminated by cobalt or nifedipine. Single calcium channels were studied by patch-clamping in the cell-attached configuration with voltage clamp pulses ranging from 0.5 to 50 s. Channel conductances (g) decreased and open times (OT) increased as clamp pulses increased in duration. For comparisons, conductances and OTs obtained with short (0.5-1 s) and long (6-12 s) pulses were grouped as SVH and LVH, respectively. SVH conductances were higher and OTs shorter when compared to LVH. BayK 8644 increased conductances and OT during SVH but this agonist decreased g during LVH. Nifedipine either eliminated channel activity, had no effects or depressed g and OT. Hypoxia (pO(2) 30 Torr) induced by 100% N(2) significantly increased calcium currents in normal bathing solutions and during exposure to 110 mM BaCl(2) in whole-cell and perforated patch recordings. Sodium dithionite (Na(2)S(2)O(4)), lowering pO(2) to 10 Torr, also increased the amplitude of calcium currents, but shifted to more positive voltages the onset and trough (maximum) of calcium currents. N(2)-induced hypoxia increased g and reduced OT during SVH but had opposite effects with longer pulses: conductance decreased and open times increased. N(2)-induced hypoxia increased the numbers of active channels (from 1 to 35) over a mean normoxic level of 47 per cell. It is suggested that increased calcium currents accompany calcium inflow in glomus cells, but calcium influx may not depend exclusively on this mechanism.

Effects of hypoxia and putative transmitters on [Ca2+]i of rat glomus cells

Dissociated rat glomus cells were loaded with Fura-2 AM to study the effects of hypoxia, and carotid body transmitters on intracellular calcium, [Ca2+]i. The mean control [Ca2+]i was 55 nM in isolated cells and 67 nM in clusters. The following procedures changed [Ca2+]i:0[Ca2+]o+EGTA reduced [Ca2+]i by about 50%, suggesting that the remaining calcium originated from intracellular organelles. [Ca2+]i increased when [Ca2+]o was doubled. Hypoxia by sodium dithionite (Na2S2O4) induced large [Ca2+]i increases in clustered and isolated cells. Smaller rises occurred with 100% N2 hypoxia. The augmented [Ca2+]i, induced by Na2S2O4, was reduced (not eliminated) in 0[Ca2+]o+EGTA, suggesting that some calcium was intracellularly released. Nifedipine depressed (did not block) the Na2S2O4-induced calcium increase, implying some inflow via other (N, T or P/Q) voltage-dependent or voltage-independent calcium channels.Cholinergic agents (ACh, nicotine, muscarine, bethanechol and pilocarpine) increased [Ca2+]i. The ACh effect was produced exclusively by calcium inflow since it was eliminated in 0[Ca2+]o+EGTA. Cholinergic effects were depressed (not obliterated) by D-tubocurarine (D-TC), hexamethonium (C6) and atropine.ACh, nicotine and pilocarpine potentiated the excitatory effect of Na2S2O4 on [Ca2+]i. Bethanechol depressed this excitation whereas muscarine had inconsistent effects. Atropine and C6 depressed [Ca2+]i increases elicited by Na2S2O4 but the effects of D-TC were variable. Dopamine (DA) had variable effects. It increased [Ca2+]i in 75% of cases, and reduced the Na2S2O4 -induced calcium increase.Thus, calcium increases during Na2S2O4 occur by direct effects on the glomus cells and feedback action through released ACh and DA.

Multidisciplinary utilization of dimethyl sulfoxide: pharmacological, cellular, and molecular aspects

DMSO is an amphipathic molecule with a highly polar domain and two apolar methyl groups, making it soluble in both aqueous and organic media. It is one of the most common solvents for the in vivo administration of several water-insoluble substances. Despite being frequently used as a solvent in biological studies and as a vehicle for drug therapy, the side-effects of DMSO (undesirable for these purposes) are apparent from its utilization in the laboratory (both in vivo and in vitro) and in clinical settings. DMSO is a hydrogen-bound disrupter, cell-differentiating agent, hydroxyl radical scavenger, intercellular electrical uncoupler, intracellular low-density lipoprotein-derived cholesterol mobilizing agent, cryoprotectant, solubilizing agent used in sample preparation for electron microscopy, antidote to the extravasation of vesicant anticancer agents, and topical analgesic. Additionally, it is used in the treatment of brain edema, amyloidosis, interstitial cystitis, and schizophrenia. Several systemic side-effects from the use of DMSO have been reported, namely nausea, vomiting, diarrhea, hemolysis, rashes, renal failure, hypertension, bradycardia, heart block, pulmonary edema, cardiac arrest, and bronchospasm. Looking at the multitude of effects of DMSO brought to light by these studies, it is easily understood how many researchers working with DMSO (or studying one of its specific effects) might not be fully aware of the experiences of other groups who are working with it but in a different context.

Behavior of junction channels between rat glomus cells during normoxia and hypoxia

The activity of gap junction channels between cultured and clustered carotid body glomus cells of the rat was studied with dual voltage clamping during normoxia (PO(2) 300 Torr) and hypoxia induced by sodium dithionite (Na(2)S(2)O(4)) or 100% N(2). Na(2)S(2)O(4) reduced the saline PO(2) to approximately 10 Torr, whereas 100% N(2) reduced ambient O(2) to approximately 60 Torr. The following observations were made. 1) In normoxia, the intercellular macroconductance (G(j) = 3.0 +/- 1.01 ns, mean +/- SE) was changed unevenly (increased and decreased) under hypoxic conditions by either agent, although N(2) produced the largest changes. 2) The intercellular microconductances of the channels (g(j) = 104.44 +/- 10.16 pS under normoxic conditions) significantly decreased in 100% N(2) but showed depressions and enhancements in Na(2)S(2)O(4). 3) The conductance of single-junction channels (SChs), calculated as g(j) variance/mean g(j), yielded a mean of approximately 17.6 pS. Larger values were obtained with manual measurements of the data (approximately 34 pS). Hypoxic hypoxia (induced by 100% N(2)) significantly depressed the conductance of SChs when calculated from digitized records or from manual measurements. Hypoxia induced by Na(2)S(2)O(4) did not significantly change junctional conductance. 4) The number of intercellular channels, calculated as g(j)/SCh g(j), had a mean of approximately 452 (range 1 to 2,471). During N(2)-induced hypoxia, this number significantly decreased to approximately 84 but remained unchanged during Na(2)S(2)O(4) hypoxia. 5) The mean open time of junction channels varied from 4 to 30 ms in different experiments, having an overall mean of mu = 11.33 +/- 0.33 ms. This value was significantly reduced by 100% N(2) but was not changed by Na(2)S(2)O(4). 6) Intracellular calcium ([Ca(2+)](i)), 46.2 +/- 4.84 nM under normoxia, significantly increased to 77.32 +/- 11.27 nM with Na(2)S(2)O(4) and to 66.39 +/- 11.64 nM with 100% N(2). It is concluded that 100% N(2) uncouples glomus cells by significantly reducing intercellular macro- and microconductances. Hypoxia induced by Na(2)S(2)O(4) had variable effects. The coupling effects of hypoxia may depend on, or be aided by, increases in [Ca(2+)](i) and/or intracellular pH changes. However, secreted transmitters and ATP plus the effects of hypoxia on second messengers and other cytoplasmic components may also play an important role in this phenomenon.

Biochemical, biophysical and haemorheological effects of dimethylsulphoxide on human erythrocyte calcium loading

The studies using dimethylsulphoxide (DMSO) and/or the 4-bromo-calcium ionophore A23187 (Br-A23187) often neglect the precise knowledge of some of their biochemical, biophysical and haemorheological effects. The aim of the present study was to evaluate these effects on erythrocytes after whole blood incubations with DMSO or Br-A23187 dissolved in DMSO. There were no significant differences between the different aliquots in the values of P(50), pH, erythrocyte deformability, erythrocyte membrane fluidity, haemoglobin and intracellular Ca(2+) concentrations ([Ca(2+)](i)). Aliquots with DMSO (independently of the presence of Br-A23187 or added Ca(2+)) had lower erythrocyte aggregation indexes and higher plasma concentrations of K(+)], Na(+)] and Ca(2+) than the aliquots without DMSO (independently of the presence of added Ca(2+)). Aliquots with added calcium (without the presence of Br-A23187 in DMSO) had a significantly higher erythrocyte acetylcholinesterase activity. Our data shows that calcium loading, the usual objective of Br-A23187 incubations, cannot be fulfilled with the studied experimental conditions. The coherence between our results and those obtained by other authors with different biological systems and different modulators of the rise on [Ca(2+)](i) suggests a non-specific effect of DMSO, disabling the action of the modulator. It can be reasoned that the decreased erythrocyte aggregation (without significant changes on the deformability or membrane fluidity) can result either from the decrease of the hydrogen bonding contribution to erythrocyte aggregation or the increased ionic strength influence on the erythrocyte membrane surface.