Live visualisation of electrolytes during mouse embryonic development using electrolyte indicators

Studies have shown that some electrolytes, including Na+ and K+, play important roles in embryonic development. However, these studies evaluated these electrolytes by using inhibitors or knockout mice, with no mention on the changes in the intracellular electrolyte concentrations during embryogenesis. In this study, we used the electrolyte indicators CoroNa Green AM and ION Potassium Green-2 AM to directly visualise intracellular concentrations of Na+ and K+, respectively, at each embryonic developmental stage in mouse embryos. We directly observed intracellular electrolyte concentrations at the morula, blastocyst, and hatching stages. Our results revealed dynamic changes in intracellular electrolyte concentrations; we found that the intracellular Na+ concentration decreased, while K+ concentration increased during blastocoel formation. The degree of change in intensity in response to ouabain, an inhibitor of Na+/K+ ATPase, was considered to correspond to the degree of Na+/K+ ATPase activity at each developmental stage. Additionally, after the blastocyst stage, trophectoderm cells in direct contact with the blastocoel showed higher K+ concentrations than in direct contact with inner cell mass, indicating that Na+/K+ ATPase activity differs depending on the location in the trophectoderm. This is the first study to use CoroNa Green AM and ION Potassium Green-2 AM in mouse embryos and visualise electrolytes during embryonic development. The changes in electrolyte concentration observed in this study were consistent with the activity of Na+/K+ ATPase reported previously, and it was possible to image more detailed electrolyte behaviour in embryo cells. This method can be used to improve the understanding of cell physiology and is useful for future embryonic development studies.

Changes in intracellular electrolyte concentrations during apoptosis induced by UV irradiation of human myeloblastic cells

Decreases in the intracellular concentrations of both K+ and Cl− have been implicated in playing a major role in the progression of apoptosis, but little is known about the temporal relationship between decreases in electrolyte concentration and the key events in apoptosis, and there is no information about how such decreases affect different intracellular compartments. Electron probe X-ray microanalysis was used to determine changes in element concentrations (Na, P, Cl, and K) in nucleus, cytoplasm, and mitochondria in U937 cells undergoing UV-induced apoptosis. In all compartments, the initial stages of apoptosis were characterized by decreases in [K] and [Cl]. The largest decreases in these elements were in the mitochondria and occurred before the release of cytochrome c. Initial decreases in [K] and [Cl] also preceded apoptotic changes in the nucleus. In the later stages of apoptosis, the [K] continued to decrease, whereas that of Cl began to increase toward control levels and was accompanied by an increase in [Na]. In the nucleus, these increases coincided with poly(ADP-ribose) polymerase cleavage, chromatin condensation, and DNA laddering. The cytoplasm was the compartment least affected and the pattern of change of Cl was similar to those in other compartments, but the decrease in [K] was not significant until after active caspase-3 was detected. Our results support the concept that normotonic cell shrinkage occurs early in apoptosis, and demonstrate that changes in the intracellular concentrations of K and Cl precede apoptotic changes in the cell compartments studied.

Subcellular electrolyte shifts during in vitro myocardial ischemia and reperfusion

Isolated perfused rabbit right ventricular wall was studied with electron probe microanalysis (EPMA) under three conditions: 1) control (37 degrees C, 1.2 Hz), 2) 60 min global ischemia, and 3) ischemia plus 5 min of reperfusion. After 60 min of ischemia, only one cell population was evident; the variance of intracellular electrolyte concentrations was the same as in controls. When compared with controls, there was no change in Ca concentration within any region of the cell, but mitochondria were swollen with K-rich fluid. Two cell populations were evident after 5 min of reperfusion. The severely injured cells were markedly swollen, exhibited hypercontraction bands, and had electrolyte profiles similar to extracellular fluid. The moderately injured cells were normal in appearance, still retained electrolyte gradients, but had elevated Na and Cl concentrations in all compartments. Cell Ca did not increase in the moderately injured cells, but the region of the cell containing the sarcoplasmic reticulum (SR) lost 90% of its Ca. Accompanying this loss were large increases in myofibrillar and mitochondrial Ca concentration. It appears that release of SR Ca, loss of SR Ca-accumulating capacity, and increased intracellular Na are the principal electrolyte shifts in functional cells during early reperfusion.

Lack of effect of acute ethanol consumption on active cation fluxes of leucocytes and erythrocytes in healthy humans

1. Acute ethanol consumption in human volunteers did not appear to alter active cation fluxes by Na+,K+-ATPase, or intracellular electrolyte concentrations, in peripheral leucocytes or erythrocytes. 2. Urinary electrolyte excretion was decreased after ethanol consumption, compared with controls. 3. Neither plasma glucose nor serum insulin was altered by ethanol. 4. After ethanol consumption there was an elevation of endogenous plasma adrenaline levels. This was accompanied by a leucocytosis, which could be attributed to a raised neutrophil count. 5. The raised adrenaline levels were not associated with hypokalaemia. 6. It is possible that in vivo ethanol may prevent adrenaline-induced hypokalaemia by fluidizing the membrane and/or decreasing the affinity of β-receptors for adrenaline.

Effect of endotoxic shock on skeletal muscle intracellular electrolytes and amino acid transport

Soleus muscle intracellular electrolytes and alpha-aminoisobutyric acid (AIB) uptake and its regulation by insulin were investigated during endotoxic shock in vivo. Fasted rats (90 g) were injected with [14C]AIB (1-10 mg/kg, iv) and Salmonella enteritidis endotoxin (20 mg/kg, iv) or saline and killed 1-5 h later. AIB uptake into muscle was corrected for uptake into extracellular space (measured as insulin distribution in muscle in vivo) and expressed as [AIB]/[AIB] ratios to assess active transport. The maximum level of active AIB cell transport by extracellular endotoxic muscles [3.3 +/- 0.2 (SE)] was lower than control muscles (4.9 +/- 0.3) at the time when plasma insulin concentration in endotoxic rats (16.8 +/- 2.0 uU/ml) was greater than controls (7.9 +/- 1.7 uU/ml). Insulin-stimulated AIB transport was significantly lower in endotoxic muscles (from a basal value of 3.3 +/- 0.2 to 4.4 +/- 0.5, 5.0 +/- 0.3, and 4.9 +/- 0.3 at 125, 250, and 500 mU/kg intravenous insulin, respectively) than in control muscles (from 4.9 +/- 0.3 to 5.7 +/- 0.2, 8.0 +/- 0.4, and 10.8 +/- 0.8). The intracellular electrolyte concentrations in endotoxic soleus muscles ([Na] = 15.87 +/- 0.9, [K] = 145 +/- 1.7, [Cl] = 14.61 +/- 0.9) were substantially altered when compared with control muscles ([Na] = 9.33 +/- 1.1, [K] = 164 +/- 1.5, [Cl] = 4.1 +/- 0.6) 5 h postinjection. The membrane potential, estimated from chloride equilibrium potential was lower in endotoxic muscles (-52.7 +/- 1.6 mV) when compared with control muscles (-89 +/- 3.5 mV).(ABSTRACT TRUNCATED AT 250 WORDS)

A family with mild hereditary xerocytosis showing high membrane cation permeability at low temperatures

1. Radioisotopic cation transport studies are described in a family whose erythrocytes had previously been found to show an abnormal net efflux of potassium when cooled to room temperature. This net efflux effect, which was inherited as an autosomal dominant trait, was associated with a few target cells on the blood film and a mild compensated haemolytic state. 2. Measurements of intracellular electrolyte concentrations, cell water and of Na+ and K+ transport rates across the membrane at 37°C were consistent with a diagnosis of mild hereditary xerocytosis. 3. Studies of cation transport in the temperature range 20–37°C revealed that the fluxes attributable to the Na+-K+ pump showed a temperature dependence comparable with that in normal cells, but that the ouabain plus loop-diuretic insensitive fluxes of K+, which probably represent the ‘passive diffusional leak’ to K+, were less sensitive to temperature than normal over the range 20–37°C. These findings were held to account for the net efflux effect previously reported.