Presence Of Nystatin Research Articles

Locally formed dopamine inhibits Na+-K+-ATPase activity in rat renal cortical tubule cells.

Dopamine, generated locally from L-dopa, inhibits Na+-K+-ATPase in permeabilized rat proximal tubules under maximum transport rate conditions for sodium. To determine whether locally formed dopamine inhibits Na+-K+-ATPase activity in intact cortical tubule cells we studied the effect of L-dopa on ouabain-sensitive oxygen consumption rate (QO2) and 86Rb uptake in renal cortical tubule cell suspensions. L-Dopa (10(-4) M) did not affect ouabain-insensitive QO2 or mitochondrial respiration. However, L-dopa inhibited ouabain-sensitive QO2 in a concentration-dependent manner, with half-maximal inhibition (K0.5) of 5 x 10(-7) M and a maximal inhibition of 14.1 +/- 1.5% at 10(-4) M (P less than 0.05). L-Dopa also blunted the nystatin-stimulated QO2 in a concentration-dependent manner, with a K0.5 of 5 x 10(-8) M and a maximal inhibition of 21.8 +/- 1.2% at 10(-5) M (P less than 0.05), indicating that L-dopa directly inhibits Na+-K+-ATPase activity and not sodium entry. Ouabain-sensitive 86Rb uptake was also inhibited by L-dopa (16.0 +/- 2.4%, P less than 0.05). Carbidopa (10(-4) M), an inhibitor of the conversion of L-dopa to dopamine, eliminated the effect of L-dopa on ouabain-sensitive QO2 and 86Rb uptake, indicating that dopamine rather than L-dopa was the active agent. The finding that the L-dopa concentration-response curve was shifted to the left by one order of magnitude in the presence of nystatin suggests that the inhibitory effect is enhanced when the intracellular sodium concentration is increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone increases the maximal turnover rate of the sodium pump.

These experiments were performed to determine whether aldosterone-dependent effects in apical and basolateral membranes could be temporarily dissociated and whether aldosterone increases the maximal capacity, or maximum turnover rate of the sodium pump. Tissue from rat distal colon exposed to the action of high plasma levels of aldosterone for 4 h, 24 h and 7-10 days was compared to control tissue in a modified Ussing chamber, before and after addition of nystatin to the mucosal solution to remove the apical barrier to the cell entry of sodium. The maximum turnover rate of the sodium pump was represented by the equivalent short circuit current, Isc, after the addition of nystatin. After 4 h of aldosterone basal Isc increased 2.6-fold above control (43 +/- 34 microA.cm-2, p less than 0.05) and transepithelial PD, VT, increased 2-fold over control (-7.0 +/- 5.5 mV, lumen negative, p less than 0.05). Administration of aldosterone for 24 h caused further marked increases in Isc (11-fold) and a fall in RT to 50% of control. Similar changes were observed after 7-10 days on low sodium diet, and at all time intervals the changes were completely inhibited by amiloride (10(-4)M). Although aldosterone stimulated Isc within 4 h, there was no further increase in Isc in the presence of nystatin during the same time period compared to the control post-nystatin Isc of 419 +/- 79 microA.cm-2. However, after 24 h aldosterone caused approximately a 40% increase in the maximal turnover rate of the sodium pump, which persisted for 7-10 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Lidocaine blockage of basolateral potassium channels in the amphibian urinary bladder.

1. Basolateral membranes of the frog urinary bladder were investigated after increasing the cationic conductance of the apical membrane by the incorporation of nystatin. 2. K+ currents were recorded in the presence of a mucosa to serosa oriented K+ gradient (SO4(2-) Ringer solution). Nystatin caused a rapid rise of the short-circuit current (Isc) followed by a slow increase over a period of 1-2 h. 3. Impedance analysis showed that the apical membrane resistance was drastically reduced by nystatin. The slow increase in Isc was accompanied by a progressive increase in basolateral conductance. 4. The transepithelial current and conductance recorded in the presence of nystatin could be depressed with lidocaine added to the mucosal and serosal solution. The effects of lidocaine were completely reversible. 5. Noise analysis showed that lidocaine induced additional fluctuations in Isc. The spectrum of these fluctuations was of the Lorentzian type. This noise component is caused by the random interruption of the current through the basolateral K+ channels. The Lorentzian parameters were used to calculate the microscopic parameters of the basolateral K+ channels.

Altérations des parois de Candida albicans cultivé en présence de doses sublétales de nystatine

Subinhibitory doses of nystatin in the culture medium of Candida albicans gave yeasts with altered cell walls. Major alterations chiefly concerned the antigenic peptidomannans. Their amount in wall and their molecular weight were smaller in yeast grown with nystatin than in normal cultured yeast. Glucans and chitin were not seriously modified. Polymers requiring lipidic intermediates such as dolichol phosphate for their biosynthesis seemed to be most affected by the presence of nystatin.

Amiloride directly inhibits the Na,K-ATPase activity of rabbit kidney proximal tubules.

Amiloride inhibited the ouabain-sensitive rate of oxygen consumption (QO2) of a suspension of rabbit intact proximal tubules in the presence of different concentrations of extracellular sodium. Measurements of the ouabain-sensitive QO2 in the presence of nystatin, the tissue sodium and potassium contents of the tubules in suspension, and the sodium- and potassium-dependent adenosinetriphosphatase (Na,K-ATPase) activity of lysed tubule membranes indicated that the effect of amiloride was due to a direct inhibition of the Na,K-ATPase activity of the proximal tubule.

Nystatin studies of the skin of larval Rana catesbeiana.

Transport and electrical characteristics of the isolated skin of larval Rana catesbeiana were analyzed using ion substitution and nystatin. When the inner (IBS) and outer (OBS) bathing solutions contained Na Ringer solution the electrical potential (TEP), short-circuit current (SCC), and resistance (R2) were 23.5 +/- 7.0 mV, 2.8 +/- 0.7 microA . cm-2, and 8.00 +/- 0.74 k omega. cm2, respectively (n = 4). When K was substituted for Na in the OBS these values were not changed significantly. When nystatin (120 U.cm-3), a drug that increases the permeability of membranes to small cations, was added to the OBS (Na Ringer) there was a striking increase in the TEP to 52.8 +/- 3.1 mV, SCC to 14.8 +/- 2.0 microA . cm-2, and drop in R2 to 3.75 +/- 0.52 k omega . cm2. The response to nystatin was similar with Na or K Ringer solution in the OBS (Na Ringer in the IBS). With Na Ringer in the OBS and IBS, the increase in SCC induced by low doses of nystatin equaled net Na flux measured isotopically. Plots of transepithelial conductance against SCC after nystatin were linear and provided estimates of shunt resistance (R*sh = 14.6 +/- 1.3 k omega . cm2) and electromotive driving force for ions (E*A = 76 +/- 3 mV). Similar curves were obtained with K Ringer in the OBS. In the presence of nystatin, characteristics of the basolateral membrane were evaluated. It displayed selective permeability to K relative to Na or Tris.

Nystatin-induced increase in photocurrent in the system ‘bacteriorhodopsin proteoliposome/bilayer planar membrane’

Proteoliposomes were reconstituted from bacteriorhodopsin sheets, asolectin and cholesterol with or without nystatin. Bacteriorhodopsin-mediated electrogenesis was monitored using (1) a proteoliposome suspension and phenyldicarbaundecaborane (PCB −) probe or (2) proteoliposomes associated with planar bilayer membrane and orthodox electrometer techniques. In the light, PCB − was shown to be taken up by proteoliposomes. The PCB − uptake was inhibited by addition of nystatin to an incubation mixture with proteoliposomes if they were reconstituted in the presence of nystatin. Extraproteoliposomal nystatin was without influence if nystatin was omitted from the reconstitution mixture. The nystatin-containing proteoliposomes were associated with a planar bilayer asolectin membrane in the presence of Ca 2+. It was found that in such a system, bacteriorhodopsin generated a photocurrent charging the proteoliposome-containing ( cis-side) compartment negatively and the trans-side compartment positively. The photoresponse was shown to be increased several-fold by addition of nystatin to the trans-side solution. Nystatin addition was ineffective if proteoliposomes were reconstituted without nystatin. Taking into account that nystatin forms ion-permeable pores in a membrane only if present on both sides of the membrane and that this membrane is bilayer, one can explain the above data assuming that (1) the intraproteoliposomal solution does not mix with the extraproteoliposomal one when proteoliposomes are attached to a planar black membrane and (2) the attached proteoliposomes are separated from the trans-side bathing solution by a bimolecular membrane. If this is the case, nystatin in the trans-side bathing solution and inside the attached proteoliposome can form pores across that part of the planar membrane which separates the proteoliposome interior from the trans-side solution. Through these pores, H + (pumped by bacteriorhodopsin from the cis-side solution into the proteoliposome interior) or some other intraproteoliposomal ions can be equilibrated with those in the trans-side solution. As a result, the bacteriorhodopsin-generated photocurrent increases.

Fusion of liposomes with planar lipid bilayers

The fusion of liposomes with planar lipid bilayers was monitored by two different methods. (a) Liposomes consisting of phospholipids and cholesterol were added to the aqueous phase bathing the cholesterol-deficient planar lipid bilayers in the presence of nystatin. The resulting increase in the planar lipid bilayer's electrical conductance was considered indicative of fusion. (b) Transplanar lipid bilayer injection of 35SO 4 2− trapped inside the liposomes. It is shown by both methods that fusion is specifically dependent on the presence of negatively charged phospholipids both in the liposomes and the planar lipid bilayers and on Ca 2+ in the aqueous phase of the fusion system.

Accumulation and storage of Zn2+ by Candida utilis.

Starved cells of Candida utilis accumulated Zn2+ by two different processes. The first was a rapid, energy- and temperature-independent system that probably represented binding to the cell surface. The cells also possessed an energy-, pH-, and temperature-dependent system that was capable of accumulating much greater quantities of the cation than the binding process. The energy-dependent system was inhibited by KCN, Na2HAsO4, m-chlorophenyl carbonylcyanide hydrazone, N-ethylmaleimide, EDTA and diethylenetriaminepenta-acetic acid. The system was specific inasmuch as Ca2+, Cr3+, Mn2+, Co2+ or Cu2+ did not compete with, inhibit, or enhance the process, Zn2+ uptake was inhibited by Cd2+. The system exhibited saturation kinetics with a half-saturation value of 1.3 muM and a maximum rate of 0.21 (nmol Zn2+) min(-1) (mg dry wt(-1)) at 30 degrees C. Zn2+ uptake required intact membranes since only the binding process was observed in the presence of nystatin, toluene, or sodium dodecyl sulphate. Cells did not exchange recently accumulated toluene, or sodium dodecyl sulphate. Cells did not exchange recently accumulated 65Zn following the addition of a large excess of non-radioactive Zn2+. Similarly, cells pre-loaded with 65Zn did not lose the cation during starvation, and efflux did not occur when glucose and exogenous Zn2+ were supplied after the starvation period. Efflux was only observed after the addition of toluene or nystatin, or when cells were heated to 100 degrees C. Cells fed a large quantity of Zn2+ contained a protein fraction resembling animal cell metallothionein. In batch culture, cells of C. utilis accumulated Zn2+ only during the lag phase and the latter half of the exponential-growth phase.

The interaction of lithium ions with the sodium-potassium pump in frog skeletal muscle.

1. The effects of external Li on Na and K efflux as well as those on K influx were studied in high Na muscles from Rana pipiens. 2. In the absence of external Ba, substitution of K-free Li for K-free Mg resulted in an increase of both Na and K efflux. The additional of ouabain produced an inhibition of Na efflux and at the same time a marked increase in the efflux of K. 3. K permeability was greatly reduced by adding 2 mM-Ba to the incubation solutions. Under these conditions, Li gave rise to a ouabain sensitive Na efflux which was 57% of that in the absence of Ba. On the other hand, the efflux of K was only slightly increased and was not affected further by ouabain. 4. The activation curves of Na efflux against the stimulating cation concentration in Na-free Mg-Ba Ringer followed a more or less hyperbolic function for both K and Li. While half-maximal activation was attained at higher concentrations of Li than of K, the maximal efflux in Li was smaller than in K. 5. The extra Na efflux produced by K was increased when Li was added to the media. This increment was not a simple additive effect and was independent of the Li concentration. In addition, at some concentrations Li increased the ouabain-sensitive K influx, whereas at others it reduced it. 6. Reversible changes in membrane permeability to monovalent cations were accomplished by incubating the muscles in the presence of Nystatin, 50 mug/ml. When internal K was reduced to values around 1-2 mumole/g (using Li as a replacement), thus minimizing the possibility of K leaking out of the cells, both Ko and Lio were able to promote a ouabain-sensitive extra efflux of Na. 7. The residual Na efflux in (K+Na)-free solutions was not affected by the removal of Ca from the media in either Mg or Li solutions, both in the absence and the presence of Ba. On the other hand, the values for the residual efflux were higher in Mg (0-00228 min-1) than in Li (0.00135 min-1). 8. These results fully support the notion that Li ions have a K-like activating action on the Na pump in muscles. In addition, they suggest that some other kind of interaction may exist between Li and the Na-K pump.

In vivo and in vitro effects of rifampicin and streptolydigin on transcription of Kluyveromyces lactis in the presence of nystatin.

Rifampicin and streptolydigin, if used in conjunction with nystatin, depress the growth of Kluyveromyces lactis. The incorporation of labeled leucine into protein is inhibited by nystatin whereas the incorporation of labeled uracil into RNA is inhibited by rifampicin in nystatin-treated cells. In order to study the mechanism of inhibition of RNA synthesis we purified by DEAE-Sephadex column chromatography four forms of RNA polymerase from K.lactis cells. The general properties of these enyzmes are similar to those of Saccharomyces cerevisiae and of other eukaryotic RNA polymerases. In particular, enzymes IA, IB and III are more active with poly[d(A-T)] template and Mn-2+ than with native or denatured calf thymus DNA. Enzyme II shows optimal activity with denatured calf thymus DNA and Mn2+. When challenged with native calf thymus DNA all enzymes prefer Mg-2+ as a divalent cation whereas with denatured calf thymus DNA all enzymes are more active with Mn-2+. Enzyme II is inhibited by lambda-amanitin but no enzyme is sensitive to rifampicin and streptolydigin. The inhibition of growth and uracil uptake observed when rifampicin is added to nystatin treated cells is probably not caused by a specific inhibition of transcription.

Transformation of a strictly coupled active transport system into a facilitated diffusion system by nystatin.

The active hexose transport system ofChlorella vulgaris is obligatorily coupled to metabolic energy. No facilitated diffusion component, as in the β-galactoside transport ofEscherichia coli, for example, is observed withChlorella. In the presence of nystatin, however, facilitated diffusion of sugar analogues occurs. Thus, only under this condition can the classical overshoot experiment be successfully carried out. The net efflux of sugars induced by nystatin does not take place through holes. It can be explained by the assumption that the mobility of the unloaded carrier is less restricted in the presence of nystatin. Nystatin also changes theKm for influx, whereas theKm for efflux is not significantly affected. Possible roles of sterols in this eucaryotic sugar transport system are discussed.