Changes In Electrolyte Concentrations Research Articles

Conformational changes of cationic potato amylopectin; influence by salt, influence by nanosized silica particles

Static light scattering was used to follow the change in conformation of a moderately charged cationic potato amylopectin. It was found that the volume of the amylopectin decreased at an increased electrolyte concentration. However, the segment density (fractal dimension) was unaffected by the change in electrolyte concentration. Furthermore, increasing the salt content increased the degree of aggregation between amylopectin molecules. Mixing the cationic amylopectin starch with nanosized silica particles did not change the globular volume of the formed polyelectrolyte complex. However, the segment density decreased at an increased concentration of silica due to an increased binding of silica particles to each amylopectin molecule. Since the silica particles are highly charged at pH 8 they try to maximize the distance between themselves causing the amylopectin molecule to follow passively, thus decreasing the segment density.

The international campaign on intercomparison between electrodes for geoelectrical measurements

In many applications of electrical geophysics, the electrodes used to detect signal seem to be an important source of noise. To identify which electrodes were most stable for electric field measurements; an international campaign to evaluate electrodes for long-term monitoring of the telluric field was held at Garchy, France from April 1995 to April 1996. More than fifty different electrode pairs from researches around the world were tested in the campaign. Most of electrodes were metal-electrolyte designs, but with different construction details. The inter-comparison was carried out through laboratory and field experiments. The results of the experiment showed a surprising variation between the performances of different electrodes. Stability as determined in a brief laboratory experiment proved to be an excellent predictor of long-term field stability. Instabilities of differing qualitative character were observed during the year-long experiment. Linear drift may be caused by gradual changes in ground contact, leaking of electrolyte, or changes in chemical concentration of electrolyte within the electrodes. Sudden onset transient noise, which could be as large as 20 mV, is likely to be an electrochemical process such as reaction charge release and charge accumulation within the electrodes. Other physical causes of drift could be due to mechanical contact problems. Of metal electrodes, stainless steel is by far the best.The conclusions from the Garchy experiment are relevant to exploration geophysics: self-potential surveys are strongly affected by the long-term stability of electrodes and some electrodes may also have internal noise exceeding 1 mV per Hz in the frequency band around 1✓Hz, thus potentially affecting measurements of Induced Polarisation data.

Rehydration following exercise: effects of administration of water versus an isotonic oral rehydration solution (ORS)

The effects of administering (1) 6L isotonic oral rehydration solution (ORS), similar in composition to plasma (except for an elevated potassium concentration) and with an osmotic skeleton and (2) 6L water (no osmotic skeleton), were evaluated in five thoroughbred horses following exercise-induced dehydration. The horses were exercised on a treadmill for 10 min at walk (1.7 m.s-1; approximately 15% VO2max), 40 min at trot (3.7 m.s-1; approximately 25% VO2max) and 10 min at walk (1.7 m.s-1; approximately 15% VO2max). Exercise was undertaken on a 3 degrees incline at 30 degrees C/80% RH. Solutions of water or ORS at 20 degrees C were administered by nasogastric tube over 60s 5 min following exercise. Mean weight loss following exercise was 9.2 +/- 1.7 kg (2.0 +/- 0.4% body weight; mean +/- SEM) with water and 9.2 +/- 1.1 kg (2.0 +/- 0.2% body weight) with ORS and was not different between treatments (P > 0.05). Water treatment resulted in a fall in plasma [Na+] (approximately 3 mmol.L-1) and C1- (1-2 mmol.L-1) concentrations by 30 min after administration and the effect persisted until the end of the study (300 min post fluids). There was little change in plasma total protein (TP) from that at the end of exercise, suggesting a failure of water to restore or maintain PV. In contrast, ORS administration resulted in a small increase in plasma [Na+] (1-2 mmol.L-1) and [Cl-] (2-3 mmol.L-1) with a corresponding decrease in plasma TP. By 120 min post ORS, plasma TP and PV were no longer significantly different from rest or pre-exercise (P > 0.05), whilst with water, TP was elevated (approximately 3-4 g.L-1) and PV reduced (approximately 4-5 mL.kg-1). Total urine output was not significantly different between water (1096 +/- 135 mL) and ORS (750 +/- 215 mL, P > 0.05). Estimates of expected plasma volume and electrolyte concentration changes as a result of either treatment compared well with measured changes of TP and PV. On the basis of calculated or measured changes, it was estimated that only 1L of water contributed to rehydration following exercise compared to 4L isotonic, plasma-like ORS. The administration of 6L ORS restored the PV deficit induced by exercise with minimal or no disturbance of plasma electrolyte concentrations. In contrast, water alone resulted in minimal improvement in PV. When fluid intake after periods of fluid loss, such as induced by exercise or transport, is not accompanied by food intake, the present study has clearly demonstrated that water alone is ineffective in promoting rehydration compared with an isotonic, plasma-like ORS.

Fluid, Electrolyte, and Acid-Base Responses to Exercise in Racehorses

During both high-intensity and short-distance exercise, the high rate of expended energy is met by anaerobic oxidation of glucose to lactic acid; this is the main cause of metabolic acidosis observed during racing. In addition, plasma volume decreases because water moves from the vasculature to the intracellular and interstitial spaces at the onset of intense exercise. These fluid shifts, together with active ion-exchange between blood and tissue, cause marked changes in electrolyte concentrations. This article reviews the mechanisms of acid-base disturbances, fluid shifts, and electrolyte changes, and discusses related areas such as buffer capacity, lactic acid distribution, and the effects of training. The influences of health, dietary cation-anion balance, supplements, and medication such as creatine, sodium bicarbonate, and furosemide are emphasized.

Effect of the Water Spectrum on the Determination of Dissolved Ammonia, Urea, and Chloride Concentrations by Raman Spectroscopy

The effect of large, changing concentrations of electrolytes on the behavior of the OH stretching band of water have been investigated with the aim of developing methods for compensating for spectral interferences when solute NH bands are made the basis for mixture analyses. With the use of urea and ammonium salts as analytes, it was found that changing electrolyte concentrations affect the shape of the water band but do not appreciably affect the shapes of either the ammonium ion or urea Raman lines. Chlorides, nitrates, and mixtures of these were used as electrolytes. The identity of the anion had a significant effect on the shape of the OH band. Two methods of compensation were used. One involved factor analyzing the spectra of a set of solutions that contained chlorides and nitrates that are Raman inactive in the vicinity of the OH stretching band. The principal abstract factors were used in place of a water reference for a least-squares mixture analysis. The other method was application of partial least-squares. In addition to urea and ammonium ion, the concentration of KCl and the ionic strength of the system can be determined in the partial least-squares approach with limits of detection better than 0.1 M.

The effect of heat exposure on performance of and recovery from high-intensity, intermittent exercise.

Environmental heat is known to hamper aerobic performance. The purpose of this study was to examine the effect of heat on the performance of anaerobic exercise and the recovery from such exercise. Eleven trained men underwent two identical exercise-recovery protocols in neutral (22 degrees C, N) and hot (35 degrees C, H) conditions, in a cross-balanced order. Exercise consisted of a series of five 15 s bouts separated by 30 s of active recovery between bouts. The 60 min resting recovery was evaluated with a subsequent exercise series. Subjects were kept euhydrated with water. Peak power developed in the initial exercise series was higher in H compared with N (720 +/- 80 vs 664 +/- 74 W, respectively, p < 0.05). In the second series of exercise, peak power slightly improved in N but decreased in H (6.1 vs -4.1 %, respectively). Mean power was higher in the initial exercise series in H compared with N (636 +/- 83 vs 584 +/- 60 W, respectively, p < 0.05). No significant change occurred in the subsequent series of exercise. There was no difference in peak lactate following the initial series, nor in the decrease of lactate during recovery between the two conditions. Likewise, there were no differences in the changes in electrolyte concentrations and serum osmolality during recovery. VO2 and heart rate decreased following exercise in a similar manner in the two conditions. Rectal temperature increased similarly but remained elevated during H compared with N (p<0.05). In conclusion, the results of this study suggest that heat exposure may improve anaerobic performance but does not appear to affect the physiological responses during 60 min of recovery. Future research should examine the effect of more extreme heat stress, as well as shorter recovery periods.

Relationship between increase in intracellular Ca 2+ concentration during global ischemia and delayed ischemic damage

The effects of administering (1) 6L isotonic oral rehydration solution (ORS), similar in composition toplasma (except for an elevated potassium concentration) and with an osmotic skeleton and (2) 6L water (no osmotic skeleton), were evaluated in five thoroughbred horses following exercise-induced dehydration. The horses were exercised on a treadmill for 10min at walk (1.7m.−1; ∼15% VO2max), 40min at trot (3.7m.−1; 25% VO2max) and l0min at walk (1.7m.rl; ∼15% VO2max). Exercise was undertaken on a 3* incline at 3°C/80% RH. Solutions of water or ORS at 20°C were administered by nasogastric tube over 60s 5 min following exercise. Mean weight loss following exercise was 9.2±l.7kg (2.010.4% body weight; meant±sem) with water and 9.2±1.1 kg (2.0±0.2% body weight) with ORS and was not different between treatments (P>0.05). Water treatment resulted in a fall in plasma [Na+] (∼3mmol.Lt) and Cl− (1–2mmol.L−1) concentrations by 30min after administration and the effect persisted until the end of the study (300min post fluids). There was little change in plasma total protein (TP) from that at the end of exercise, suggesting a failure of water to restore or maintain PV. In contrast, ORS administration resulted in a small increase in plasma [Na+] (1–2mmol.L−1) and [Cl−] (2-3mmol.L−1) with a corresponding decrease in plasma TP. By 120min post ORS, plasma TP and PV were no longer significantly different from rest or pre-exercise (P>0.05), whilst with water, TP was elevated (∼3–4g.L−1) and PV reduced (∼4–5mL.kg−1). Total urine output was not significantly different between water (1096±135mL) and ORS (750±215mL, P>0.05). Estimates of expected plasma volume and electrolyte concentration changes as a result of either treatment compared well with measured changes of TP and PV. On the basis of calculated or measured changes, it was estimated that only 1 L of water contributed to rehydration following exercise compared to 4 L isotonic, plasma-like ORS. The administration of 6 L ORS restored the PV deficit induced by exercise with minimal or no disturbance of plasma electrolyte concentrations. In contrast, water alone resulted in minimal improvement in PV. When fluid intake after periods of fluid loss, such as induced by exercise or transport, is not accompanied by food intake, the present study has clearly demonstrated that water alone is ineffective in promoting rehydration compared with an isotonic, plasma-like ORS.

Effects of Royal Jelly on the Humoral Antibody Response and Blood Chemistry of Chickens

Al-Mufarrej, S.I. and El-Sarag, M.S.A. 1997. Effects of royal jelly on the humoral antibody response and blood chemistry of chickens. J. Appl. Anim. Res., 12: 41–47. The effects of royal jelly (RJ) on primary and secondary antibody responses against sheep red blood cells (SRBC) and on blood chemistry were studied in 40 chickens of either sex. The birds were divided into 4 equal groups A, B, C and D, each consisting of 5 male and 5 female birds. At 8 weeks of age, the birds of groups B and C were treated each with 200 mg RJ, given orally or subcutaneously, respectively. Simultaneously, both groups, as well as group A were immunized each with 0.2 ml of 10% SRBC suspension in PBS and re- immunized 10 days later with a second similar dose. Group D served as non-immunized control. Treatment witu RJ increased antibody production against SRBC in groups B and C, as compared to group A, while non-significant changes in concentrations of electrolytes and other blood constituents were recorded in the RJ-treated birds, apart from a decrease in K and cholesterol concentrations. Further studies on these lines have been recommended.

Sprint training enhances ionic regulation during intense exercise in men.

1. This study investigated the effects of 7 weeks of sprint training on changes in electrolyte concentrations and acid-base status in arterial and femoral venous blood, during and following maximal exercise for 30 s on an isokinetic cycle ergometer. 2. Six healthy males performed maximal exercise, before and after training. Blood samples were drawn simultaneously from brachial arterial and femoral venous catheters, at rest, during the final 10 s of exercise and during 10 min of recovery, and analysed for whole blood and plasma ions and acid-base variables. 3. Maximal exercise performance was enhanced after training, with a 13% increase in total work output and a 14% less decline in power output during maximal cycling. 4. The acute changes in plasma volume, ions and acid-base variables during maximal exercise were similar to previous observations. Sprint training did not influence the decline in plasma volume during or following maximal exercise. After training, maximal exercise was accompanied by lower arterial and femoral venous plasma [K+] and [Na+] across all measurement times (P < 0.05). Arterial plasma lactate concentration ([Lac-]) was greater (P < 0.05), but femoral venous plasma [Lac-] was unchanged by training. 5. Net release into, or uptake of ions from plasma passing through the exercising muscle was assessed by arteriovenous concentration differences, corrected for fluid movements. K+ release into plasma during exercise, and a small net K+ uptake from plasma 1 min post-exercise (P < 0.05), were unchanged by training. A net Na+ loss from plasma during exercise (P < 0.05) tended to be reduced after training (P < 0.06). Release of Lac- into plasma during and after exercise (P < 0.05) was unchanged by training. 6. Arterial and venous plasma strong ion difference ([SID]; [SID] = [Na+] + [K+] - [Lac-] - [Cl-]) were lower after training (mean differences) by 2.7 and 1.8 mmol l-1, respectively (P < 0.05). Arterial and femoral venous CO2 tensions and arterial plasma [HCO3-] were lower after training (mean differences) by 1.7 mmHg, 4.5 mmHg and 1.2 mmol l-1, respectively (P < 0.05), with arterial plasma [H+] being greater after training by 2.2 nmol l-1 (P < 0.05). 7. The acute changes in whole blood volume and ion concentrations during maximal exercise were similar to previous observations: Arterial and femoral whole blood [K+] and [Cl-] were increased, whilst [Na+] was lower, across all observation times after training (P < 0.05). 8. Net uptake or release of ions by exercising muscle was assessed by arteriovenous whole blood concentration differences, corrected for fluid movements. A net K+ uptake by muscle occurred at all times, including exercise, but this was not significantly different after training. An increased net Na+ uptake by muscle occurred during exercise (P < 0.05) with greater Na+ uptake after training (P < 0.05). Net muscle Lac- release and Cl- uptake occurred at all times (P < 0.05) and were unchanged by training. 9. Sprint training improved muscle ion regulation, associated with increased intense exercise performance, at the expense of a greater systemic acidosis. Increased muscle Na+ and K+ uptake by muscle during the final seconds of exercise after training are consistent with a greater activation of the muscle Na(+) - K+ pump, reduced cellular K+ loss and the observed lesser rate of fatigue. The greater plasma acidosis found after sprint training was caused by a lower arterial plasma [SID] due to lower plasma [K+] and [Na+], and higher plasma [Lac-].

Circadian Changes in Electrolyte Concentration in Plasma and Erythrocytes in Two-week-old Calves

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Interactions between Adsorbed Gelatin Layers

The interaction energies between gelatin coated surfaces at various electrolyte and pH conditions have been determined and are reported. These experiments were performed by attaching a small glass sphere to an AFM tip, allowing the gelatin to adsorb, and then moving the AFM tip toward an optically flat surface. The importance of adsorption conditions as well as the current conditions are discussed. A number of general trends have been observed. The layer was seen to expand with increasing pH. At low pH the surfaces are negative and the gelatin positive and thus the polyampholyte tends to lay relatively flat. As the pH is increased the strong interaction between the surface and polyampholyte decreases and so the gelatin extends away from the surface. On changing electrolyte concentration, no effect was seen at the isoelectric point, however, the layer was observed to swell at more alkaline pHs.By oscillating the AFM tip as the surfaces are moved together and determining the response of the tip to the oscillation, some mechanical properties of the gelatin may be obtained. In particular, the viscoelastic properties may be determined from the amplitude of oscillation and the phase lag of the response. The results show that when the adsorbed gelatin layers interact, the response changes from being primarily viscous to primarily elastic in nature and as the adsorbed layers are compressed further an almost entirely elastic response is noted.

HYDRAULIC CONDUCTIVITY, DISPERSION AND OSMOTIC EXPLOSION IN ARID-ZONE SOILS LEACHED WITH ELECTROLYTE SOLUTIONS

The maintenance of an appropriate soil structure and favorable soil hydraulic conductivity (HC) is critical for the sustainability of irrigated soils. Clay dispersion and/or swelling satisfactorily explain the observed reductions in HC at relatively low electrolyte concentrations (C) and/or relatively high sodium adsorption ratios (SAR). However, uncertainties still remain with regard to the mechanisms responsible for observed reductions in HC at relatively high C and/or low SAR values. Our objective was to determine the effect of a range of C and SAR values on clay dispersion and HC of four calcareous, micaceous, arid-zone soils and to ascertain the contribution of the osmotic explosion effect to the observed HC reductions at high electrolyte concentrations. We determined the saturated HC and clay dispersion in the leachates of soil and soil:sand (1:2 w/w) columns equilibrated at successively diluted electrolyte concentrations of 500, 100, 50, 10, 5, 3, and 1 meq L−1 of SAR 0 and 10 (meq L−1)0.5, followed by deionized water (C < 0.01 meq L−1). The observed decreases in HC at C levels below the flocculation value (FV, i.e., minimum C without clay dispersion) of these soils were attributed to clay dispersion and partial plugging of conducting pores. A total dispersed clay of less than 2 g kg−1 soil (i.e., less than 0.8% of the total soil clay in the column) was responsible for a cumulative 72% reduction in HC, indicating that very small quantities of dispersed clay had a dramatic effect on the water-conducting properties of these soils. Significant decreases in HC also occurred at C levels well above those at which dispersed clay appeared in the leachate. The estimated threshold electrolyte concentrations (Ct at which HC starts to decrease) were higher than the corresponding FV of these soils, indicating that clay dispersion was not responsible for the observed reductions in HC. The steepest reductions in HC originated in systems where the steepest concentration gradients developed between the micropores and the macropores (i.e., in the soil:sand columns, close to the advancing front of the displacing solution and for changes in electrolyte concentrations from 500 to 100 meq L−1). We concluded that an osmotic explosion effect (i.e., the osmotic water movement into, macroscopic swelling within, and the destruction or slaking of the aggregate) was responsible for the observed HC reductions at these high electrolyte concentrations.

Modulation of interaction forces between bilayers exposing short-chained ethylene oxide headgroups

The use of liposomes as drug delivery systems has been limited by their rapid clearance from circulation by the mononuclear phagocyte system. Recent studies have found that circulation times can be greatly enhanced by incorporating a small amount of modified lipids whose headgroups are derivatized with a bulky water soluble polymeric chain of poly ethylene oxide. We report here a systematic study using the Surface Forces Apparatus to measure directly the interactions between two phosphatidyl ethanolamine lipid bilayers, exposing this polymeric headgroup at different concentrations in the bilayer. We found that the force becomes repulsive at all separations and that the thickness of the steric barrier could be controlled easily by adjusting the concentration of the modified lipids. Equilibrium force profiles were measured that were reversible and largely insensitive to changes in electrolyte concentration and temperature. The results have enabled the Dolan and Edwards theory for the steric forces of low coverage polymer surfaces and the Alexander de Gennes theory for high coverage surfaces to be tested, and both were found to apply. We conclude that these simple theories can be used to model the interactions of surprisingly short segments and, hence, apply to such systems as lipids with bulky headgroups and liposomes containing a sterically stabilizing polymer.

ISFET responses on a stepwise change in electrolyte concentration at constant pH

Responses on a stepwise increase of the electrolyte concentration of bare ISFETs can interfere with responses of an ISFET with an affinity membrane deposited on the gate. In this paper the responses of bare ISFETs are studied. Results of experiments and simulations are presented and the mechanism is explained.

Luminescence lifetimes of aqueous europium perchlorate, chloride and nitrate solutions

The sensitivity of the half life of Eu(II) luminescence to changes in electrolyte concentration has been studied. The values of n, the hydration number, were calculated and found to increase for HClO 4, LiClO 4 and NaClO 4 solutions and to decrease for NaCl and LiNO 3 solutions as the concentrations were increased. In HCl solution, n increased with concentration to 5 M, then decreased. These observations are discussed in terms of models of outer vs. inner sphere complexation and of increased interaction of the primary hydration sphere with the Eu(II) cation.

Chapter 19: The development of ion regulation at the blood-brain barrier

Electrolytes play an essential part in neuronal activity and normal central nervous system (CNS) function is dependent on ion regulation in both the intra- and extracellular fluids of the brain. In particular, both K + and Ca 2+ are important ions for neuronal function. It has been known for a long time that changing electrolyte concentrations in the cerebrospinal fluid (CSF) has marked effects on nervous activity, whereas changing electrolyte concentrations in blood has minimal effects in brain. The blood–brain barrier (BBB), sited at the brain capillary endothelium, together with the blood–CSF barrier at the choroid plexus epithelium, controls transfer to the brain of substances in the systemic circulation as well as transfer in the reverse direction. Very early brain capillaries may be permeable to large molecules and even have fenestrations. By late gestation in the rat and mouse, however, the BBB is tight to proteins, although smaller molecules such as inulin and sucrose penetrate into brain and CSF more readily in both late fetal and neonatal rats.

Changes in the concentrations of Na+, K+ and Cl- in secretion from the skin during progressive increase in exercise intensity.

A simple method for sampling skin secretion in 1-min periods was developed for investigating the effects of progressive increases in exercise intensity on Na+, K+ and Cl- secretions from the skin of the forearm. Ten healthy male subjects performed exercise consisting of eight stepwise increases in intensity from 50 to 225 W, with a 25-W increase at each step. Exercise at each step was for 3 min followed by a 1-min recovery period. Samples of blood and skin secretion were taken during the recovery period. Significant positive correlations were found between the mean concentrations of Na+ and Cl- and between those of K+ and Cl- in the skin secretion. The concentrations of electrolytes in the skin secretion also showed significant correlations with the blood lactate concentrations. The inflection points for secretions of Na+, K+ and Cl- were 4.04, 3.61 and 3.83 mmol.l-1 of blood lactate; 64.42, 61.96 and 62.14% of maximal oxygen consumption (VO2max); and exercise intensities of 123.01, 117.65 and 125.07 W, respectively. No significant differences were observed between the value of 67.27% of VO2max or 134.00W at the onset of blood lactate accumulation (OBLA) and the inflection points. From these results we concluded that changes in electrolyte concentrations in skin secretion during incremental exercise according to this protocol were closely related with the change in the blood lactate concentration, and that the inflection points for electrolytes may have been near the exercise intensity at OBLA.

Electrostatic interaction between ion-penetrable multi-layered membranes

A theory of the double layer interaction regulated by the Donnan potential between two ion-penetrable membranes in an electrolyte solution developed previously by Ohshima and Kondo is extended to the case in which the membranes consist of many layers having different thickness and densities of membrane-fixed charges. The interaction force is found to be determined mainly by the contributions from layers located within the depth of 1/kappa (kappa, Debye-Hückel parameter) from the membrane surface. It is also predicted that the interaction force may alter its sign with changing electrolyte concentration.

The roles of ion fluxes in skeletal muscle fatigue

Intense muscle contractions result in large changes in the intracellular concentrations of electrolytes. The purpose of this study was to examine the contributions of changes in intracellular strong ions to calculated changes in steady-state membrane potential (Em) and muscle intracellular H+ concentration ([H+]i). A physicochemical model is used to examine the origin of the changes in [H+]i during intense muscle contraction. The study used the isolated perfused rat hindlimb intermittently stimulated to contract at high intensity for 5 min. This resulted in significant K+ depletion of both slow (soleus) and fast (white gastrocnemius, WG) muscle fibers and a release of K+ and lactate (Lac-) into venous perfusate. The major contributor to a 12- to 14-mV depolarization of Em in soleus and WG was the decrease in intracellular K+ concentration ([K+]i). The major independent contributors to [H+]i are changes in the concentrations of strong and weak ions and in CO2. Significant decreases in the strong ion difference [( SID]i) in both soleus and WG contributed substantially to the increase in [H+]i during stimulation. In WG the model showed that the decrease in [SID]i accounted for 35% of the increase in [H+]i (133-312 nequiv/L; pHi = 6.88-6.51) at the end of stimulation. Of the main contributors to decreased [SID]i, increased [Lac-]i and decreased [K+]i contributed 40 and 60%, respectively, to increased [H+]i, whereas a decrease in [PCr2-]i contributed to reduced [H+]i. It is concluded that decreased muscle [K+]i during intense contractions is the single most important contributor to reduced Em and increased [H+]i. Depletion of PCr2- simultaneous to the changes in [Lac-]i and [K+]i prevents larger increases in [H+]i and helps maintain the intracellular acid-base state.

Effects of deoxycorticosterone acetate on muscle electrolytes, resting potential and mitochondria in rats.

Deoxycorticosterone acetate, injected daily for 5, 10, 20 or 30 days, reduced the serum potassium levels of rats by about 25%, a decrease that was independent of the treatment period employed. Serum sodium concentrations were unchanged with treatment duration. The potassium concentrations in extensor digitorum longus (EDL) and soleus (SOL) muscles were significantly decreased, and those of sodium increased, after treatment. Accompanying these changes of electrolyte concentration, the resting membrane potentials of treated EDL and SOL were hyperpolarized in vivo, and showed depolarization with the decreases of external potassium concentrations in vitro. The mitochondria in the muscles of treated rats were damaged. The degree of damage was more serious in EDL than in SOL and was dependent on the duration of deoxycorticosterone acetate treatment.