Intracellular Electrolyte Research Articles

High- or low-potassium solutions for the storage of abdominal and thoracic organs.

Clinically, intracellular type solutions are the most widely used solutions to preserve organs. The optimal ion composition of preservation solutions, however, is still unknown and extracellular-type solutions have frequently been superior to intracellular solutions in various experimental studies. In this study, we measured extracellular (interstitial) electrolyte concentrations in rat livers, kidneys, hearts and lungs at 4 degrees C by means of microdialysis sampling. After 24 h cold ischaemia, [Na+]int and [K+]int were 104 +/- 25 mmol/l and 6.5 +/- 0.7 mmol/l in hearts, 92 +/- 12 mmol/l and 6.9 +/- 1.0 mmol/l in livers, 115 +/- 22 mmol/l and 6.3 +/- 0.9 mmol/l in kidneys and 87 +/- 17 mmol/l and 6.4 +/- 0.6 mmol/l in lungs. After preservation of organs in intracellular-type solutions, [Na+]int was significantly lower for each organ (range from 69 +/- 8 mmol/l to 73 +/- 20 mmol/l) and [K+]int was significantly higher (range from 8.0 +/- 1.7 mmol/l to 9.8 +/- 1.0 mmol/l). In no instance did the interstitial electrolyte concentration equilibrate with the intracellular electrolyte concentration. When the diffusion gradient from the vascular space to the interstitial space was calculated for Na+ and K+, a significantly higher barrier was found for K+ than for Na+ (P<0.001 and P<0.01 for hearts). These studies indicate that during cold storage of rat hearts, lungs, livers and kidneys, intra- and extracellular electrolytes do not equilibrate. Ion exchange stabilises at extracellular Na+ concentrations between 87 mmol/l and 115 mmol/l and K+ concentrations between 6.3 mmol/l and 6.9 mmol/l. Storage of organs in solutions with extracellular-type ion compositions might improve graft function and survival not only after lung and liver but also after heart and renal preservation.

The Influence of Surface Charges on the Conductance of the Human Connexin37 Gap Junction Channel

The single-channel conductance of the hCx37 homotypic gap junction channel does not saturate with transjunctional voltages up to ±75 mV, nor does it depend linearly on the intracellular electrolyte concentration. The average maximum unitary conductances measured in KCl were 175 pS (30 mM), 236 pS (55 mM), 343 pS (110 mM), and 588 pS (270 mM) in the presence of 0.1 mM MgCl 2. The unexpectedly high unitary conductance at low salt concentrations can be explained by fixed charge groups within or near the channel orifice. Fixed cytoplasmic surface charges (3.4 e) positioned adjacent (15 Å) to the channel pore adequately model the data (surface charge density of 0.24 e/(nm) 2). In other experiments, high Mg 2+ reduced the unitary conductance of hCx37 homotypic gap junction channels more than predicted by screening alone, consistent with specific effects of Mg 2+ on the channel.

Cryopreservation of competent intact yeast cells for efficient electroporation

We have developed a simple method for cryopreserving Schizosaccharomyces pombe and Saccharomyces cerevisiae competent intact cells that permits high transformation efficiency and long-term storage for electroporation. Transformation efficiency is significantly decreased if intact cells are frozen in common permeating cryoprotectants such as glycerol or dimethyl sulphoxide. On the other hand, we found that a high transformation efficiency could be maintained if the cells were frozen in a non-permeating cryoprotectant such as sorbitol. The optimum concentration of sorbitol was found in a hypertonic solution of around 2 M. It was also very important to use S. pombe cells grown in minimal medium and S. cerevisiae cells grown in nutrient medium in the exponential growth phase. A slow freezing rate of 10 degrees C/min and a rapid thawing rate of 200 degrees C/min resulted in the highest transformation efficiency. We also found it necessary to wash the thawed cells with 1.0 M of non-electrolyte sorbitol, since the intracellular electrolytes had leaked as a result of cryoinjury. The frozen competent cells stored at -80 degrees C could be used for more than 9 months without any loss of transformation efficiency. This cryopreservation method for electroporation is simple and useful for routine transformations of intact cells. Frozen competent cells offer the advantages of long-term storage with high efficiency and freedom from the preparation of fresh competent cells for each transformation.

Microbeam PIXE analysis of Na, K, Mg, and Ca in severely damaged cardiac tissue.

The aim of the study was to measure with microbeam PIXE elements such as Na, K, Mg, and Ca in cardiac tissue after various treatments in vivo, which affect the cardiomyocyte integrity. It was assumed that local deviations from normal electrolyte levels indicate the degree of cardiac damage. The first step in this feasibility study was comparison of severely damaged cardiac tissues with controls. Severe cardiac damage was introduced by the so-called Ca paradox. Experiments were performed with isolated rat hearts, perfused retrogradely with an oxygenated crystalloid buffer. Results indicated that severe cardiac damage was accompanied with almost complete disappearance of the normal intracellular electrolyte composition as a result of the loss of membrane integrity. Identifications of smaller and more locally present ischemic damages on basis of altered electrolyte levels appeared to be feasible. However, the prerequisite was that the mobility of electrolytes be kept under control during tissue sampling and sample preparation, when physiological mechanisms stop to maintain gradients.

The electrical properties of leg skin in normal individuals and in patients with ischemia

Measurements of skin electrical admittance were performed on the leg in healthy controls and patients with ischemia. The experiments were carried out using sinusoidal wave voltage at seven frequencies from 100 Hz to 100 kHz applied using two electrodes. The character of the frequency dependencies of admittance for both groups arises from stratum corneum — in the frequencies up to 10 kHz, and the underlying tissue of skin, above this frequency. Legs change their passive electrical properties due to ischemia. The measured data are interpreted as cell membranes become more permeable and thus an efflux of intracellular electrolyte.

Effect of estrogen replacement therapy on blood pressure and intracellular electrolytes

Effect of estrogen replacement therapy on blood pressure and intracellular electrolytes

INTRACELLULAR DIMETHYLSULFOXIDE (DMSO) IN UNICELLULAR MARINE ALGAE: SPECULATIONS ON ITS ORIGIN AND POSSIBLE BIOLOGICAL ROLE

Recent studies have established that aqueous phase concentrations of dimethylsulfoxide (DMSO) often exceed those of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS). Yet, in comparison to DMSP and DMS, DMSO remains a poorly understood component of the marine sulfur cycle. Much of what is known about the mechanisms for the formation and loss for DMSO is inferred from laboratory experiments, and no explanation exists to rationalize how a large pool of DMSO is maintained. One formation pathway that, until very recently, has been ignored involves the direct synthesis of DMSO by marine phytoplankton. This review examines some of the circumstantial evidence for DMSO in marine particulate material and recent reports containing preliminary data for particulate DMSO (DMSOp) in the marine environment. Drawing on literature from a range of scientific disciplines, speculations on the possible origins and biological functions of intracellular DMSO are also made. On the basis of its physicochemical properties, intracellular DMSO could have a potential role as a cryoprotectant, a specialist cryo‐osmoregulator in extreme environments, an intracellular electrolyte modifier, and a free‐radical scavenger. The review also assesses the impact of DMSOp at both the organism and the global level. Consideration is given to the marine biogeochemical cycling of sulfur and potential links to climate control.

Intracellular ionic strength regulates the volume sensitivity of a swelling-activated anion channel

Cell swelling activates an outwardly rectifying anion channel termed VSOAC (volume-sensitive organic osmolyte/anion channel). Regulation of VSOAC by intracellular electrolytes was characterized in Chinese hamster ovary cells by whole cell patch clamp. Elevation of intracellular CsCl concentration from 40 to 180 mM resulted in a concentration-dependent decrease in channel activation. Activation of VSOAC was insensitive to the salt gradient across the plasma membrane, the intracellular concentration of specific anions or cations, and the total intracellular concentration of cations, anions, or electrolytes. Comparison of cells dialyzed with either CsCl or Na2SO4 solutions demonstrated directly that VSOAC activation is modulated by intracellular ionic strength (microi). The relative cell volume at which VSOAC current activation was triggered, termed the channel volume set point, decreased with decreasing ionic strength. At microi = 0.04, VSOAC activation occurred spontaneously in shrunken cells. The rate of VSOAC activation was nearly 50-fold higher in cells with microi = 0.04 vs. those with microi = 0.18. We propose that microi modulates the volume sensor responsible for channel activation.

Intracellular electrolyte levels and transport of secretory granules in exocrine gland cells

We demonstrate the intracellular transport of secretory granules of a silk protein, fibroin, from the Golgi region to the apical cytoplasm with special reference to microtubule organization, electrolyte concentrations and the acidic intragranular pH of normal and mutant posterior silk gland cells, using the techniques of electrophysiological microelectrode and microprobe analysis and of light and electron microscopic autoradiography. The silk gland cells of a recessive mutant making only flimsy cocoons were defective in the microtubule systems, did not stain with an anti-tubulin antibody in immunofluorescent microscopy, and accumulated intracellular granules in the apical and basal cytoplasm. The increase in intracellular calcium concentration and levels of chloride secretion were also reduced in the mutant cells. A carboxylic ionophore, monensin, which collapsed the granular H+ gradient, induced the transport of chloride and an increase in the intracellular calcium concentration, while it blocked the intracellular transport of granules from the Golgi region to the apical cytoplasm in normal cells. Thus, we conclude that the H+ gradient across the membrane of secretory granules is responsible for the intracellular transport of the secretory granules along the microtubule systems in silk gland cells, while Ca2+ is thought to be required for the exocytosis of the granules.

RAPID ALDOSTERONE-INDUCED CELL VOLUME INCREASE OF ENDOTHELIAL CELLS MEASURED BY THE ATOMIC FORCE MICROSCOPE

Atomic force microscopy (AFM) is a useful technique for imaging the surface of living cells in three dimensions. The authors applied AFM to obtain morphological information of individual cultured endothelial cells of bovine aorta under stationary and strain conditions and to simultaneously measure changes in cell volume in response to aldosterone. This mineralocorticoid hormone is known to have acute, non-genomic effects on intracellular pH, intracellular electrolytes and inositol-1,4,5-triphosphate production. In this study whether endothelial cells under tension change their volume in response to aldosterone was tested. Such changes were already shown in human leukocytes measured by Coulter counter. In contrast to leukocytes that are more or less spherical and live in suspension, endothelial cells exhibit a complex morphology and adhere to a substrate. Thus, measurements of discrete cell volume changes in endothelial cells under physiological condition is only feasible with more sophisticated techniques. By using AFM we could precisely measure the absolute cell volume of individual living endothelial cells. Before the addition of aldosterone the cell volume of mechanically stressed endothelial cells mimicking arterial blood pressure was 1827±172fl. Cell volume was found to increase by 28% 5min after hormone exposure. Twenty-five minutes later cell volume was back to normal despite the continuous presence of aldosterone in the medium. Amiloride, a blocker of the plasma membrane Na+/H+exchanger prevented the initial aldosterone-induced volume increase. Taken together, AFM disclosed a transient swelling of endothelial cells induced by the activation of an aldosterone sensitive plasma membrane Na+/H+exchanger.

MEASUREMENT AND ANALYSIS OF MOISTURE CHANGES IN AGRICULTURAL PRODUCTS USING FFT NOISE IMPEDANCE SPECTROSCOPY

ABSTRACT Macroscopically, cellular foods including agricultural products are regarded as the electrical systems in which cell membranes isolate intracellular electrolytes from extracellular electrolytes. Moisture movement in the materials during drying causes the changes in moisture of the intracellular and extracellular electrolytes. Therefore, the moisture movements can be detected by an electrical measurement The authors measured the impedance of carrot roots during drying by a FFT (fast Fourier transform) noise impedance method at frequency of 40 Hz to 100 kHz. The equivalent circuit model agreed with the measured impedance. The parameters in the model were determined as the intracellular and extracellular resistances and membrane capacitance As a result, it was found that the increase in the extracellular resistance showed a good correlation with a decrease in moisture content between 200 and 400% d.b (dry basis) and that the membrane capacitance had the maximum near the second critical moisture content. It was concluded that the FFT noise impedance method was applicable to the moislure measurement of agricultural products during drying.

Intracellular electrolytes regulate the volume set point of the organic osmolyte/anion channel VSOAC.

Regulation of the volume sensitivity of the swelling-activated organic osmolyte/anion channel VSOAC by intracellular electrolytes was examined in intact and patch-clamped C6 glioma cells. In intact cells, VSOAC activation was monitored by [3H]taurine efflux measurements, and intracellular electrolyte concentrations were manipulated by acclimation to hypertonic medium for varying periods of time. Hypertonic shrinkage was followed by a rapid and complete regulatory volume increase mediated by electrolyte accumulation that elevated intracellular Na+, K+, and Cl- concentrations. During prolonged (4-48 h) exposure to hypertonicity, electrolyte concentrations decreased gradually as cells accumulated the organic osmolyte myo-inositol. VSOAC activation induced by cell swelling of 35-40% increased as a function of the time of exposure to hypertonicity and was inversely correlated with measured intracellular Na+, K+ and Cl- levels. In patch-clamped cells, swelling-induced Cl- current activation was unaffected by acclimation conditions but was inhibited by increasing the concentration of electrolytes in the patch pipette solution. Quantification of the relationship between VSOAC activation and cell swelling demonstrated that increases in intracellular electrolyte levels increase VSOAC volume set point. Regulation of VSOAC volume sensitivity by electrolytes allows cells to selectively utilize electrolytes or a combination of electrolytes and organic osmolytes for regulatory volume decrease (RVD). Control over the type of solute used for volume regulation is advantageous, allowing cells to control intracellular ionic composition and prevent increases in cytoplasmic ionic strength during RVD.

Response of myocardial cellular energy metabolism to variation of buffer composition during open-chest experimental cardiopulmonary resuscitation in the pig.

The aim of the present study was to investigate possible relationships in piglets between myocardial energy-related metabolites and intracellular electrolytes during open-chest cardiopulmonary resuscitation (OCCPR) supplemented by the administration of alkaline buffers with varying sodium content. Our hypothesis was that an increasing myocardial intracellular sodium content would decrease the intracellular energy stores. In addition to haemodynamics, acid-base and blood gas variables were analysed, and myocardial biopsies were collected before and during OCCPR as well as after the return of spontaneous circulation. After a period of 4 min of untreated ventricular fibrillation (VF). 25 piglets were randomly allocated to one of four groups: OCCPR with normal saline (n = 5); OCCPR with sodium bicarbonate (SB) (n = 7); OCCPR with Tris buffer mixture (TBM) (n = 7); and a totally untreated control group (n = 6). The results showed that 4 min of untreated VF almost eradicated creatine phosphate (CrP) and that the ATP/ADP ratio decreased to 1.5-2.0. During OCCPR with normal saline, the myocardial content of CrP increased, whereas lactate, ATP and ADP levelled off and AMP decreased, causing an increased ATP/ADP ratio. The adenosine and inosine contents increased, whereas inosine monophosphate was unchanged at a low level, the adenosine and inosine contents being inversely correlated with the total content of adenine nucleotides. In both buffered groups, the increase in most energy-related metabolites (CrP, ATP, ADP, AMP and the ATP/ADP quotient) was less and in lactate more pronounced than in the group not being buffered, with no difference between the groups receiving SB or TBM. Although the intracellular potassium content was unaltered, the sodium, chloride and calcium concentration increased, more so in the group receiving SB. The intracellular content of sodium was correlated with that of calcium. Thus, buffering increased the myocardial AMP degradation during OCCPR by increasing the flux via the 5'-nucleotidase reaction, and SB increased the intracellular contents of sodium and calcium to a greater extent than did TBM.

Effects of Cadmium on Electrolyte Ions in Cultured Rat Hepatocytes Studied by X-Ray Microanalysis of Cryosections

The distribution of elements in isolated and cultured rat hepatocytes was measured by energy dispersive electron probe X-ray microanalysis of freeze-dried ultrathin cryosections. The intracellular compartmentation of electrolyte ions, in particular the content of sodium, chloride, and potassium, was found to depend on culture conditions and on the amount of cadmium chloride added to the culture medium. In cells exposed to 1–10 μmcadmium without carbon dioxide supply, the potassium/sodium ratio decreased from control values of about 10 to values below 1 within 30 min. Changes of potassium and sodium content were followed by an increase in the intracellular chloride content. In cells exposed to 1–10 μmcadmium with carbon dioxide supply, changes of the electrolyte composition were delayed to 1–2 days. An increase of intracellular chloride preceded the inversion of the intracellular potassium/sodium ratio. High cadmium doses induced a cytoplasmic calcium increase and finally disintegration and decay of cell structure. Almost normal potassium and sodium contents were found in cells exposed to 10 μmcadmium in the presence of 100 μmzinc with carbon dioxide for 1 day. Changes in the intracellular electrolyte composition by adverse or toxic conditions were detected before any structural damage became visible. Thus, energy dispersive electron probe X-ray microanalysis of cryosections proved to be a sensitive probe of cell viability and cytotoxicity.

Nongenomic effects of aldosterone on intracellular calcium in porcine endothelial cells.

Rapid in vitro effects of aldosterone on intracellular electrolytes, cell volume, and the sodium-proton antiport have been described in human mononuclear leukocytes and vascular smooth muscle cells. In the present study, we demonstrate rapid aldosterone effects on free intracellular calcium as determined by fura 2 fluorometry in single porcine endothelial cells. After addition of 100 nmol/l aldosterone, cells respond with a sustained rise in free intracellular calcium by approximately 50% of initial levels within 1-5 min. Elevations are predominantly seen in the subplasmalemmal space. Effective half-maximal concentration values for aldosterone are approximately 1 pmol/l and for cortisol approximately 1 nmol/l. These effects are blunted in calcium-free medium and absent after pretreatment by thapsigargine. They remain unchanged by a >1,000-fold excess of spironolactone. These findings indicate the existence of a nongenomic pathway for aldosterone action in porcine endothelial cells and may be related to known rapid cardiovascular effects of aldosterone in vivo mediated through the baroreceptor reflex.

Modulation of ouabain sensitive sodium potassium pump of erythrocytes from patients with chronic renal failure:Role of acute hemodialysis

Significantly higher levels of plasma urea creatinine and potassium were observed in patients with renal failure compared to normal controls. The RBC sodium concentration was raised whereas the RBC potassium concentration was decreased in chronic renal failure. These alterations in the RBC Na+ and K+ concentrations were associated with decrease in ouabain sensitive sodium efflux rate and ouabain sensitive sodium efflux rate constant. However, there was no significant impact of acute hemodialysis on the intracellular electrolytes levels, ouabain sensitive sodium efflux rate and ouabain sensitive sodium efflux rate constant. These findings suggest an intrinsic alteration in the transport capacity of Na(+)-K+ pump which could account for the rise in intracellular sodium and fall in intracellular potassium content in the RBCs of chronic renal failure patients.

Acute infusion of amphotericin B: Proximal tubular effects

Summary: Electron microprobe analysis (EMPX) was employed to determine the alterations in intracellular electrolyte concentrations in proximal tubular cells resulting from acute treatment with amphotericin B. Concurrent clearance data confirmed a drop in glomerular filtration rate (GFR) in the rats treated with amphotericin B infusion (1 mg/kg per h) compared to control animals infused with saline (0.69 ± 0.11 vs 1.27 ± 0.08 mL/min per 100 g; P &lt; 0.001). Measurement of intracellular electrolytes in proximal tubular cells in mmol/kg wet weight by EMPX demonstrated no difference in Na (16.2 ± 0.6 vs 17.2 ± 0.5) or K (129.7 ± 2.1 vs 131.3 ± 2.0). Intracellular Rb accumulation following acute infusion was significantly reduced in the amphotericin B treated animals (3.9 ± 0.4 vs 6.6 ± 0.4; P &lt; 0.0001), suggestive of a reduction in basolateral Na‐K ATPase activity. These results do not support the tenet that amphotericin B causes a generalized increase in epithelial cell membrane ionic permeability, nor direct tubular toxicity in the doses and time frame studied. Rather, they suggest that a primary reduction in GFR results acutely in a load‐dependent decrease in proximal tubular Na transport.

Anoxia in vitro does not induce neuronal swelling or death

To improve the understanding of neuronal cell swelling in cerebral ischemia, cell volume regulation, viability, intracellular electrolytes, and lactate production of Neuro-2A neuroblastoma cells were studied using an in vitro model. The volume regulatory capacity of Neuro-2A cells was assessed after incubation in hypo- and hypertonic media. Anoxia was studied alone and together with inhibition of glycolysis by iodoacetate. Reducing the tonicity of the incubation medium to 250, 200, or 150 mosm/l caused immediate swelling followed by a regulatory volume decrease within 20 min, which, however, was not complete. The final cell volume after regulation depended on the tonicity of the medium and remained above control. There was no regulatory volume increase after cell shrinking in hypertonic media. Despite the severe anisotonic incubation, viability decreased only slightly without reaching statistical significance. In contrast to in vivo conditions, anoxia for 90 min with or without iodoacetate for additional inhibition of anaerobic energy metabolism neither caused neuronal cell swelling nor a decrease of viability. Reoxygenation after the anoxic period also did not induce volume and viability changes. Intracellular K + of Neuro-2A cells was markedly decreased, while Na + increased in a 1:1 ratio during complete energy failure by anoxia plus iodoacetate. A similar effect, occurring however somewhat delayed, was seen when the Neuro-2A suspension was exposed to iodoacetate alone. Anoxia without inhibition of glycolysis had no effect on intracellular ion concentrations, but lactate production was nearly six times higher than normal. In vitro, with a large extracellular volume and sufficient glucose supply, the energetic demands of Neuro-2A cells to maintain stable transmembraneous ion gradients during anoxia are obviously met by anaerobic glycolysis. The current results confirm that neuronal cells are able to adequately regulate cell volume in response to hyposmotic stress. On the other hand, maintenance of a normal cell size during complete energy deprivation suggests strongly that energy failure per se does not suffice to induce neuronal swelling. Cell swelling in cerebral ischemia in vivo thus appears a secondary phenomenon due to mediator mechanisms such as tissue acidosis or elevated extracellular glutamate levels.

Anoxia in vitro does not induce neuronal swelling or death

To improve the understanding of neuronal cell swelling in cerebral ischemia, cell volume regulation, viability, intracellular electrolytes, and lactate production of Neuro-2A neuroblastoma cells were studied using an in vitro model. The volume regulatory capacity of Neuro-2A cells was assessed after incubation in hypo- and hypertonic media. Anoxia was studied alone and together with inhibition of glycolysis by iodoacetate. Reducing the tonicity of the incubation medium to 250, 200, or 150 mosm/l caused immediate swelling followed by a regulatory volume decrease within 20 min, which, however, was not complete. The final cell volume after regulation depended on the tonicity of the medium and remained above control. There was no regulatory volume increase after cell shrinking in hypertonic media. Despite the severe anisotonic incubation, viability decreased only slightly without reaching statistical significance. In contrast to in vivo conditions, anoxia for 90 min with or without iodoacetate for additional inhibition of anaerobic energy metabolism neither caused neuronal cell swelling nor a decrease of viability. Reoxygenation after the anoxic period also did not induce volume and viability changes. Intracellular K+ of Neuro-2A cells was markedly decreased, while Na+ increased in a 1:1 ratio during complete energy failure by anoxia plus iodoacetate. A similar effect, occurring however somewhat delayed, was seen when the Neuro-2A suspension was exposed to iodoacetate alone. Anoxia without inhibition of glycolysis had no effect on intracellular ion concentrations, but lactate production was nearly six times higher than normal. In vitro, with a large extracellular volume and sufficient glucose supply, the energetic demands of Neuro-2A cells to maintain stable transmembraneous ion gradients during anoxia are obviously met by anaerobic glycolysis. The current results confirm that neuronal cells are able to adequately regulate cell volume in response to hyposmotic stress. On the other hand, maintenance of a normal cell size during complete energy deprivation suggests strongly that energy failure per se does not suffice to induce neuronal swelling. Cell swelling in cerebral ischemia in vivo thus appears a secondary phenomenon due to mediator mechanisms such as tissue acidosis or elevated extracellular glutamate levels.

Chronic volume expansion in the rat: proximal tubular Na+ transport and Na+ pump inhibition.

1. The lesser natriuresis of chronic volume expansion (ChVE) compared with that of acute volume expansion (AcVE) implies different homeostatic mechanisms. Because little information is available in the literature on proximal tubular (PT) Na+ transport and intracellular electrolyte concentrations, these were investigated in a rat model of ChVE. 2. Haematocrit was significantly lower and urine volume and Na+ excretion were significantly higher in ChVE rats compared with control rats. 3. Proximal tubular Na+ transport with artificial PT fluid was normal (3.67 +/- 0.09 x 10(-4) mm3 mm-2 s-1; mean+/-S.E.M.), while with endogenously harvested tubular fluid it was reduced to 2.78 +/- 0.07 x 10(-4) mm3 mm-2 s-1 in ChVE rats (P < 0.0001). 4. Intracellular Na+ was significantly elevated from 18.0 +/- 0.7 mmol (kg wet wt)-1 in control rats to 20.2 +/- 0.8 mmol (kg wet wt)-1 in ChVE rats (P = 0.044). The cells showed residual swelling, with dry weight and phosphorus values decreasing significantly compared with controls (19.5 +/- 0.4 to 18.5 +/- 0.03% and 130.4 +/- 3.7 to 117.8 +/- 2.8 mmol (kg wet wt)-1, P = 0.04 and 0.006, respectively). 5. The results demonstrate that in ChVE a tubular factor inhibits PT Na+ transport associated with an inhibition of the Na+ pump and this resembles one mechanism defined in AcVE.