Nystatin Treatment Research Articles

Clustering of the B cell receptor is not required for the apoptotic response.

We examined the role of BCR cell membrane redistribution in anti-IgM-induced apoptosis in three human B cell lines, RA#1, 2G6, and MC116, that differ in their relative levels of sIgM expression. The apoptotic response was found to be dependent on the nature of the anti-IgM and the cell line. In the cell lines, RA#1 and MC116, sIgM aggregated into patches that were insensitive to the disruption of cholesterol-rich membrane microdomains by nystatin or beta-MCD. The B cell line 2G6 was able to reorganize sIgM into a tight coalescent cap upon anti-IgM treatment. However, in this case, the lipid raft inhibitors nystatin and beta-MCD disrupted the patching. In 2G6 cells, BCR-mediated apoptosis was not affected by nystatin treatment, whereas it increased in beta-MCD pretreated cells. Thus, no evident correlation was found between apoptosis and BCR cell membrane redistribution or lipid raft formation in either of the three cell lines. The data indicate that the apoptotic signal transduction pathway is independent of BCR translocation into lipid rafts and/or aggregation.

Nystatin prophylaxis and treatment in severely immunodepressed patients.

Nystatin is sometimes used prophylactically in patients with severe immunodeficiency or in the treatment of fungal infection in such patients, although the effect seems to be equivocal. To study whether nystatin decreases morbidity and mortality when given prophylactically or therapeutically to patients with severe immunodeficiency. MEDLINE and The Cochrane Library using a comprehensive search strategy. Contacted industry and scanned reference lists. Randomised trials comparing nystatin with placebo, an untreated control group, fluconazole or amphotericin B. Data on mortality, invasive fungal infection and colonisation were extracted by both authors independently. The outcomes were weighted by the inverse variance. A random effects model was used unless p>0.10 for the test of heterogeneity. We included 10 trials (1, 122 patients). The drugs were given prophylactically in eight trials and as treatment in two. Six trials were in acute leukaemia, one mainly in cancer, one in liver transplant patients, one in critically ill surgical and trauma patients, and one in AIDS patients. Nystatin had been compared with placebo in three trials and with fluconazole in seven; the dose varied from 1.5 MIE to 72 MIE daily. The effect of nystatin was similar to that of placebo on fungal colonisation (relative risk 0.85, 95% confidence interval 0. 65 to 1.13). There was no difference between fluconazole and nystatin on mortality (relative risk 0.87, 0.52 to 1.44) whereas fluconazole was more effective in preventing invasive fungal infection (relative risk 0.42, 0.16 to 1.12) and colonisation (relative risk 0.50, 0.36 to 0.71). The results were very similar if the three studies which were not performed in cancer patients were excluded. Nystatin cannot be recommended for prophylaxis or treatment of Candida infections in immunodepressed patients.

Functional profiling of the Saccharomyces cerevisiae genome

Determining the effect of gene deletion is a fundamental approach to understanding gene function. Conventional genetic screens exhibit biases, and genes contributing to a phenotype are often missed. We systematically constructed a nearly complete collection of gene-deletion mutants (96% of annotated open reading frames, or ORFs) of the yeast Saccharomyces cerevisiae. DNA sequences dubbed 'molecular bar codes' uniquely identify each strain, enabling their growth to be analysed in parallel and the fitness contribution of each gene to be quantitatively assessed by hybridization to high-density oligonucleotide arrays. We show that previously known and new genes are necessary for optimal growth under six well-studied conditions: high salt, sorbitol, galactose, pH 8, minimal medium and nystatin treatment. Less than 7% of genes that exhibit a significant increase in messenger RNA expression are also required for optimal growth in four of the tested conditions. Our results validate the yeast gene-deletion collection as a valuable resource for functional genomics.

Isolation of High-Malate-Producing Sake Yeasts from Low-Maltose-Assimilating Mutants.

High-malate-producing sake yeasts were isolated from low-maltose-assimilating mutants. A sake yeast Kyokai no. 701 (K-701) was mutagenized with ethyl methanesulfonate. After nystatin treatment, low-maltose-assimilating mutants were selected using a replica plating method. The forty-two mutants obtained were fermented in koji extract medium and almost all of them produced more malate than the parental strain. In a small-scale sake brewing test, several of these mutants produced 2.3 to 6.7 times higher concentrations of malate and 1.5 to 2.1 times higher total acidity than the parental strain. However, these mutants exhibited neither resistance to cycloheximide nor sensitivity to dimethyl succinate, which are used as the phenotypes for isolation of high-malate-producing sake yeasts. The expression levels of the MDH and FUM1 genes in one mutant (M20), which produced the highest amount of malate among the mutants obtained, were analyzed by Northern hybridization. The transcriptional level of the FUM1 gene in strain M20 during sake brewing had a similar profile to that in strain K-701. However, the transcriptional level of the MDH2 gene in strain M20 for days 4 and 8 of malate formation during sake brewing was higher than that in strain K-701.

Isolation of high-malate-producing sake yeasts from low-maltose-assimilating mutants

High-malate-producing sake yeasts were isolated from low-maltose-assimilating mutants. A sake yeast Kyokai no. 701 (K-701) was mutagenized with ethyl methanesulfonate. After nystatin treatment, low-maltose-assimilating mutants were selected using a replica plating method. The forty-two mutants obtained were fermented in koji extract medium and almost all of them produced more malate than the parental strain. In a small-scale sake brewing test, several of these mutants produced 2.3 to 6.7 times higher concentrations of malate and 1.5 to 2.1 times higher total acidity than the parental strain. However, these mutants exhibited neither resistance to cycloheximide nor sensitivity to dimethyl succinate, which are used as the phenotypes for isolation of high-malate-producing sake yeasts. The expression levels of the MDH and FUM1 genes in one mutant (M20), which produced the highest amount of malate among the mutants obtained, were analyzed by Northern hybridization. The transcriptional level of the FUM1 gene in strain M20 during sake brewing had a similar profile to that in strain K-701. However, the transcriptional level of the MDH2 gene in strain M20 for days 4 and 8 of malate formation during sake brewing was higher than that in strain K-701.

Na+]i, [K+]i and [Cl-]i regulation of exocytosis in guinea-pig antral mucous cells.

Effects of intracellular Na+, K+ and Cl- on Ca(2+)-regulated exocytosis activated by 10 microM acetylcholine (ACh) were studied in guinea-pig antral mucous cells which are permeabilized by nystatin treatment. Ca(2+)-regulated exocytotic events were modulated by [Na+]i, [K+]i and [Cl-]i via mediation of PTX-sensitive G proteins. Increases in [Na+]i and PTX inhibit G protein (G(Na)), which suppressed the exocytosis. Increases in [K+]i caused the exchange of G proteins (from G(Na) to G(K)) to increase, and GK evoked activation of the exocytosis and was inhibited by PTX. Increases in [Cl-]i and PTX inhibit G protein (G(Cl)), which stimulates exocytotic events. Based on these observations, the exocytosis in antral mucous cells were modulated by intracellular ions, concentration of which were increased or decreased by cell volume changes caused by Ach.

Inhibition of Ca(2+) entry caused by depolarization in acetylcholine-stimulated antral mucous cells of guinea pig: G protein regulation of Ca(2+) permeable channels.

The effects of depolarizing conditions resulting from increasing extracellular K(+) concentration or nystatin treatment on intracellular Ca(2+) concentration ([Ca(2+)](i)) were studied in guinea pig antral mucous cells following acetylcholine (ACh) stimulation. ACh stimulation evoked a biphasic increase in [Ca(2+)](i), that is, an initial transient increase followed by a plateau. Depolarizing conditions reduced the [Ca(2+)](i) in the plateau phase during ACh stimulation. However, pertussis toxin (PTX, a G protein inhibitor) treatment caused [Ca(2+)](i) in the ACh-evoked plateau phase to increase under depolarizing conditions, while it had no effect on [Ca(2+)](i) under hyperpolarized conditions. Based on these observations, Ca(2+) permeable channels are regulated by a G protein which is activated by depolarized conditions and inhibited by hyperpolarized conditions and PTX; activation of the G protein (depolarization) causes Ca(2+) permeable channels to inhibit, and in turn, inhibition of the G protein (hyperpolarization) causes them to activate.

Expression of Mutant Dynamin Protects Cells against Diphtheria Toxin but Not against Ricin

Diphtheria toxin is believed to enter sensitive mammalian cells via receptor-mediated endocytosis from clathrin-coated pits, while ricin can enter via both clathrin-dependent and clathrin-independent endocytosis. The present study has confirmed this by determining the toxin sensitivity of COS-7y cells which were transiently overexpressing atransdominant negative mutant of dynamin, a GTPase required for the budding of clathrin-coated vesicles from the plasma membrane. Cells overexpressing wild-type dynamin showed normal receptor-mediated endocytosis of transferrin and remained sensitive to both diphtheria toxin and ricin. Cells overexpressing a mutant dynamin defective in GTP binding and hydrolysis were unable to endocytose transferrin and were protected against diphtheria toxin, but they remained completely sensitive to ricin intoxication. Treating nontransfected cells or cells overexpressing mutant dynamin with nystatin caused a redistribution of the caveolae membrane marker protein VIP21-caveolin from the cell surface to intracellular locations, but did not affect their sensitivity to ricin. The redistribution of caveolin seen after nystatin treatment may reflect the disappearance of caveolae. If this is the case, caveolae are not responsible for the endocytosis of ricin. An alternative clathrin-independent route may operate for ricin, since cellular uptake, intracellular transport, and translocation into the cytosol remain unaffected when clathrin-dependent endocytosis is effectively blocked.

K+ transport and capacitance of the basolateral membrane of the larval frog skin.

Skin from larval bullfrogs was mounted in an Ussing-type chamber in which the apical surface was bathed with a Ringer solution containing 115 mM K+ and the basolateral surface was bathed with a Ringer solution containing 115 mM Na+. Ion transport was measured as the short-circuit current (Isc) with a low-noise voltage clamp, and skin resistance (Rm) was measured by applying a direct current voltage pulse. Membrane impedance was calculated by applying a voltage signal consisting of 53 sine waves to the command stage of the voltage clamp. From the ratio of the Fourier-transformed voltage and current signals, it was possible to calculate the resistance and capacitance of the apical and basolateral membranes of the epithelium (Ra and Rb, Ca and Cb, respectively). With SO4(2-) as the anion, Rm decreased rapidly within 5 min following the addition of 150 U/ml nystatin to the apical solution, whereas Isc increased from 0.66 to 52.03 microA/cm2 over a 60-min period. These results indicate that nystatin becomes rapidly incorporated into the apical membrane and that the increase in basolateral K+ permeability requires a more prolonged time course. Intermediate levels of Isc were obtained by adding 50, 100, and 150 U/ml nystatin to the apical solution. This produced a progressive decrease in Ra and Rb while Ca and Cb remained constant. With Cl- as the anion, Isc values increased from 2.03 to 89.57 microA/cm2 following treatment with 150 U/ml nystatin, whereas with gluconate as the anion Isc was only increased from 0.63 to 11.64 microA/cm2. This suggests that the increase in basolateral K+ permeability produced by nystatin treatment, in the presence of more permeable anions, is due to swelling of the epithelial cells of the tissue rather than the gradient for apical K+ entry. Finally, Cb was not different among skins exposed to Cl-, SO4(2-), or gluconate, despite the large differences in Isc, nor did inhibition of Isc by treatment with hyperosmotic dextrose cause significant changes in Cb. These results support the hypothesis that increases in cell volume activate K+ channels that are already present in the basolateral membrane of epithelial cells.

Induction of tyrosine phosphorylation and Na+/H+ exchanger activation during shrinkage of human neutrophils.

The ubiquitous isoform of the Na+/H+ exchanger (NHE1) is essential for the regulation of cellular volume. The underlying molecular mechanism, which is poorly understood, was studied in human polymorphonuclear leukocytes (PMN). Suspension of PMN in hypertonic media induced rapid cellular shrinkage and activation of NHE1, which is measurable as a cytosolic alkalinization. Concomitantly, hypertonic stress also induced extensive tyrosine phosphorylation of several proteins. Pretreatment of PMN with genistein, a tyrosine kinase inhibitor, prevented not only the tyrosine phosphorylation in response to a hypertonic shock but also the activation of NHE1. The signal elicited by hyperosmolarity that induces activation of tyrosine kinases and NHE1 was investigated. Methods were devised to change medium osmolarity without altering cell volume and vice versa. Increasing medium and intracellular osmolarity in normovolemic cells failed to activate tyrosine kinases or NHE1. However, shrinkage of cells under iso-osmotic conditions stimulated both tyrosine phosphorylation and NHE1 activity. These findings imply that cells detect alterations in cell size but not changes in osmolarity or ionic strength. The identity of the proteins that were tyrosine-phosphorylated in response to cell shrinkage was also investigated. Unexpectedly, the mitogen-activated protein kinases SAPK, p38, erk1, and erk2 were not detectably phosphorylated or activated. In contrast, the tyrosine kinases p59(fgr) and p56/59(hck) were phosphorylated and activated upon hypertonic challenge. We propose that cells respond to alterations in cell size, but not to changes in osmolarity, with increased tyrosine phosphorylation, which in turn leads to the activation of NHE1. The resulting changes in ion content and cytosolic pH contribute to the restoration of cell volume in shrunken cells.

Nystatin prophylaxis in immunocompromised children.

In conclusion, the use of nystatin for fungal prophylaxis in hematology/oncology/bone marrow transplantation patients appears to convey little or no benefit over no therapy. Nystatin treatment significantly reduced the frequency of multiple-site colonization and of persistently positive oropharyngeal cultures, but was not able to prevent the occurrence of disseminated fungal infections. Other antifungal agents (e.g., ketoconazole, fluconazole, itraconazole, oral or intravenous amphotericin B) may be of benefit. Studies comparing nystatin with other agents are available in the literature but are beyond the scope of this review.

Nystatin-rhodamine B assay for estimating activity of killer toxin from Kluyveromyces lactis.

Killer toxin activity is commonly determined by the well test (), which ensures the inhibition zone on a substratum of sensitive strain cells. The Rhodamine B assay described in Chapter 31 is based on estimation of the fraction of killed cells, which stain with the fluorescent dye Rhodamine B. Nevertheless, this test cannot be used to assess the effect of Kluyveromyces lactis killer toxin, since it does not render sensitive cells permeable to this stain but merely causes a Gl block in the cell cycle (). It was, however, expected that killing yeast cells other than by the toxin, e.g., with nystatin, would also make them stainable by Rhodamine B. A clear-cut killing effect of nystatin was only observed in exponentially growing cells, whereas stationary cells were much less susceptible (,). At the exponential growth phase, nystatin-treated Saccharomyces cerevisiae cells stain with Rhodamine B, if they have not previously been exposed to killer toxin produced by Kluyveromyces lactis. This finding constitutes the principle of a method for estimating the activity of this toxin (). The fraction of unstained cells increases in dependence on concentration of killer toxin in medium. As the lowered sensitivity of exponentially growing S. cerevisiae culture to nystatin after exposure to this toxin is owing to its inhibitory effect, it would probably be possible to determine in similar manner the activity of any inhibitor that suppresses the growth of cells in the exponential phase. The main disadvantage of the original version of the nystatin-Rhodamine B assay () is that the protective effect against nystatin caused by treating exponentially growing cells with toxin, develops rather slowly. An improved nystatin-Rhodamine B assay presented here is based on the observation that the susceptibility to nystatin in the absence of killer toxin is fully developed in all cells after 3 h of cultivation of diluted stationary culture at 28°C, whereas in the presence of appropriately concentrated samples of killer toxins all stationary phase cells are protected. Determination of the intermediate concentrations of killer toxin capable of protecting 50% of cells against nystatin treatment (PD50) can be used to characterize the relative activity of a killer toxin preparation.

Antifungal Prophylaxis in Severely Neutropenic Patients: How Much Fluconazole is Necessary?

OBJECTIVES: To evaluate the efficacy of low dose fluconazole treatment for the prevention of yeast colonization and infection in severely neutropenic patients. METHODS: An open randomized trial, comparing fluconazole (100 mg per day) with nystatin (800,000 IU per day), in a University Hospital setting. RESULTS: Antifungal prophylaxis was given during the period of neutropenia, defined as less than 500 polymorphonuclear cells (PMN)/mm3). Thirty-six patients were randomly assigned to fluconazole and 33 to nystatin treatment groups. New oropharyngeal colonizations were significantly reduced by fluconazole (P=0.005), and oropharyngeal infections occurred less frequently in the fluconazole group (3% versus 16%, P=0.07). Stool colonization was identical between both groups. Systemic fungal infections were rare; one fluconazole patient had pulmonary aspergillosis and one nystatin patient developped Candida pseudotropicalis fungemia. Empiric amphotericin B was given with the same frequency in both groups. No side effects were associated with fluconazole. However, the administration of nystatin became impossible for three patients because of vomiting and lack of compliance. CONCLUSIONS: Fluconazole (100 mg per day) is more effective than nystatin for the prevention of oropharyngeal yeast colonization. Comparison with results in the literature suggests that a 100-mg dose of fluconazole has similar effects to 200 or 400 mg per day.

Isolation of a cold-sensitive fermentation mutant of a baker's yeast strain and its use in a refrigerated dough process.

Conventional baker's yeast converts sugars in dough into CO2 and ethanol to a significant extent when the dough is stored for days at 5 degrees C. We have isolated Csf (cold-sensitive fermentation) mutants of a commercial baker's yeast by a selection method including as the critical step a nystatin treatment to mutagenized cells at 10 degrees C in the presence of antimycin A. The fermentative activity of mutant strain CSF3 was substantially zero at 5 degrees C and one-fifth that of the parent at 10 degrees C but was restored to the same level as the parental activity at 25 to 40 degrees C. In contrast with the parent, the mutant strain normally produced white bread dough and butter roll dough even after the dough was stored for a week at 5 degrees C.

Na-K-Cl cotransport in nystatin-treated tracheal cells: regulation by isoproterenol, apical UTP, and [Cl

Chloride secretion in mammalian airway epithelia is stimulated by beta-adrenergic agonists via an adenosine 3',5'-cyclic monophosphate (cAMP)-dependent mechanism and by apical triphosphate nucleotides (ATP, UTP) via a cAMP-independent mechanism. Both types of secretagogues are known to stimulate apical Cl channels in airway cells; however, to maintain a stimulated rate of secretion, basolateral Cl influx via Na-K-Cl cotransport must be upregulated in parallel with apical Cl efflux. To examine the regulation of basolateral cotransport activity and its relationship to apical Cl efflux, we examined Cl transport in confluent primary cultures of dog tracheal epithelial cells treated with nystatin, an antibiotic that increases the permeability of plasma membranes to small monovalent ions, including Cl. By applying nystatin to the apical membrane of these cultures, apical Cl permeability could be increased to the point where transepithelial Cl transport is limited by transport across the basolateral membrane, which reflects primarily the activity of the cotransporter. In cultures of tracheal cells not treated with nystatin, transepithelial (basolateral-to-apical) 36Cl flux was increased two- to threefold by exposure to isoproterenol (5 microM, basolateral) or apical UTP (10 microM). Apical application of nystatin (400 units/ml) increased the basal level of transepithelial 36Cl flux approximately 1.5-fold and eliminated UTP stimulation of this flux, although an approximately twofold stimulation by isoproterenol persisted. Nystatin treatment also abolished UTP stimulation of saturable, basolateral [3H]bumetanide binding, a measure of functioning Na-K-Cl cotransporters in these cells; isoproterenol stimulation of binding was only mildly inhibited by nystatin treatment. Lowering intracellular Cl concentration ([Cl]i) by incubating cultures with apical media containing nystatin and reduced [Cl] (NO3 replacement) increased both basolateral-to-apical 36Cl flux and [3H]bumetanide binding in the absence of secretagogues or cell shrinkage. The results support our previous suggestion, based entirely on [3H]bumetanide binding [M. Haas, D. G. McBrayer, and J. R. Yankaskas. Am. J. Physiol. 264 (Cell. Physiol. 32): C189-C200, 1993], that UTP stimulation of basolateral Na-K-Cl cotransport in airway epithelial cells is entirely secondary to, and requires, an increase in apical Cl efflux, and further suggest that a decrease in [Cl]i may be a signal for cotransport activation in response to UTP. In addition, a cAMP-dependent cascade initiated by isoproterenol appears to directly stimulate the cotransporter.

Munchausen Syndrome by Proxy in a Saudi Child

Munchausen Syndrome by Proxy in a Saudi Child

Stevens-Johnson Syndrome Associated With Nystatin Treatment

To the Editor.— Nystatin is a polyene antibiotic, derived fromStreptomyces noursei. It is widely used for the treatment ofCandida albicansinfections, and is considered to be a safe medication, virtually nontoxic and nonsensitizing.1 However, hypersensitivity reactions to nystatin have been rarely reported. The following case is, to the best of my knowledge, the first report of erythema multiforme major associated with nystatin treatment. Report of a Case.— A 14-month-old, previously healthy girl was treated with nystatin (Mycostatin) oral suspension for thrush. On the third day of treatment, a maculopapular eruption appeared over her trunk and limbs, and lasted for 2 days. One week later, she again received nystatin oral suspension because of reappearance of oral candidiasis. Within a few hours, maculopapular lesions appeared over her face, trunk, and limbs, including the palms and soles. The medication was discontinued and the eruption regressed. Ten days later, she was reexamined

Stevens-Johnson syndrome associated with nystatin treatment

Stevens-Johnson syndrome associated with nystatin treatment

Interactions of external and internal H+ and Na+ with Na+/Na+ and Na+/H+ exchange of rabbit red cells: Evidence for a common pathway

We have studied the kinetic properties of rabbit red cell (RRBC) Na+/Na+ and Na+/H+ exchanges (EXC) in order to define whether or not both transport functions are conducted by the same molecule. The strategy has been to determine the interactions of Na+ and H+ at the internal (i) and external (o) sites for both exchanges modes. RRBC containing varying Nai and Hi were prepared by nystatin and DIDS treatment of acid-loaded cells. Na+/Na+ EXC was measured as Nao-stimulated Na+ efflux and Na+/H+ EXC as Nao-stimulated H+ efflux and delta pHo-stimulated Na+ influx into acid-loaded cells. The activation of Na+/Na+ EXC by Nao at pHi 7.4 did not follow simple hyperbolic kinetics. Testing of different kinetic models to obtain the best fit for the experimental data indicated the presence of high (Km 2.2 mM) and low affinity (Km 108 mM) sites for a single- or two-carrier system. The activation of Na+/H+ EXC by Nao (pHi 6.6, Nai less than 1 mM) also showed high (Km 11 mM) and low (Km 248 mM) affinity sites. External H+ competitively inhibited Na+/Na+ EXC at the low affinity Nao site (KH 52 nM) while internally H+ were competitive inhibitors (pK 6.7) at low Nai and allosteric activators (pK 7.0) at high Nai. Na+/H+ EXC was also inhibited by acid pHo and allosterically activated by Hi (pK 6.4). We also established the presence of a Nai regulatory site which activates Na+/H+ and Na+/Na+ EXC modifying the affinity for Nao of both pathways. At low Nai, Na+/Na+ EXC was inhibited by acid pHi and Na+/H+ stimulated but at high Nai, Na+/Na+ EXC was stimulated and Na+/H+ inhibited being the sum of both pathways kept constant. Both exchange modes were activated by two classes of Nao sites, cis-inhibited by external Ho, allosterically modified by the binding of H+ to a Hi regulatory site and regulated by Nai. These findings are consistent with Na+/Na+ EXC being a mode of operation of the Na+/H+ exchanger. Na+/H+ EXC was partially inhibited (80-100%) by dimethyl-amiloride (DMA) but basal or pHi-stimulated Na+/Na+ EXC (pHi 6.5, Nai 80 mM) was completely insensitive indicating that Na+/Na+ EXC is an amiloride-insensitive component of Na+/H+ EXC. However, Na+ and H+ efflux into Na-free media were stimulated by cell acidification and also partially (10 to 40%) inhibited by DMA; this also indicates that the Na+/H+ EXC might operate in reverse or uncoupled modes in the absence of Na+/Na+ EXC.(ABSTRACT TRUNCATED AT 400 WORDS)

Ca2+-activated K+ efflux limits complement-mediated lysis of human erythrocytes.

The lytic effect of complement on human erythrocytes has been reported by others to increase when Na+ is substituted for K+ in the external medium. In this paper we have investigated the hypothesis that net loss of K+ through a K+ transport pathway protects erythrocytes from complement-induced colloidosmotic swelling and lysis. Antibody-sensitized human erythrocytes containing different intracellular cation concentrations (nystatin treatment) were exposed to low concentrations of guinea pig serum in media of different cation composition; complement lysis was assessed by the release of hemoglobin and the volume of the surviving cells estimated by their density distribution profiles. Complement-dependent swelling and lysis of erythrocytes (a) were limited by the presence of an outwardly directed K+ electrochemical gradient and (b) were enhanced by carbocyanine, a specific inhibitor of the Ca2+-activated K+ transport pathway, and by absence of Ca2+ in the external medium. We propose that during complement activation a rising cytosolic calcium triggers the Ca2+-activated K+ permeability pathway, the Gardos effect, produces a net K+, Cl- and water loss, and thus limits the colloidosmotic swelling and lysis of erythrocytes.