Erythrocyte Potassium Concentrations Research Articles

Ion-Selective Electrodes for Measuring Potassium in Erythrocytes: a Model for Clinical Interpretation of the Results (a Pilot Study).

Potassium content in erythrocytes was measured using a blood gas analyzer with ion-selective electrodes in parallel with the laboratory procedure. Patients from intensive care units were randomly selected for the study. No correlations of potassium with other plasma parameters have been found, however its buffer dependence on chlorine in plasma has been established. Minimal value of potassium concentration in erythrocytes (for 356 measurements) was 68.2 mmol/L, maximal - 210.2 mmol/L.Following the logic of the acid-base status, a nomogram for clinical interpretation of intracellular potassium homeostasis has been developed. The low values are mainly connected with the deficit of potassium which is impossible to determine in blood plasma (e.g. in severe metabolic alkalosis or diuretic therapy). The elevated concentration of potassium in erythrocytes is caused by eryptosis: released potassium is absorbed by normal erythrocytes (protection from hyperkalaemia). So, the increased concentration of potassium indicates directly the presence of eryptosis triggers, i.e. inflammatory mediators, oxidative stress, and others, for example in sepsis. The results of the study have shown that measurement of potassium concentration in erythrocytes with the help of ion-selective electrodes is an effective method of monitoring its intracellular homeostasis. Potassium in erythrocytes is an independent biological marker which can provide clinically relevant information.

Correlation between gamma-background of environment and indicators of electrolyte metabolism in patients with arterial hypertension depending on the variant of antihypertensive therapy

Arterial hypertension and ischemic heart diseases continue to lead among cardiovascular diseases. In this regard, an importance of fixed-combination antihypertensive therapy is noted. There is an evidence that in years of high solar activity in a group of healthy persons and patients with arterial hypertension and ischemic heart disease reduces the quality of professional activity, cardiovascular diseases exacerbate so that some patients end up developing a heart attack or stroke. There was revealed the correlation between γ-background dynamics of the external environment (within the boundaries of the regional standards) and indicators of electrolyte metabolism in patients with arterial hypertension with different temperament and anxiety, which take an empirical variant of antihypertensive therapy or another variant targeted to the blockade of temperamental peculiarities of psychosomatic status, the most effective antihypertensive therapy was determined. When the power of γ-background in medium was increased, the concentration of potassium and magnesium in blood serum and erythrocytes decreased, but the concentration of sodium increased as the erythrocyte resistance decreased. These shifts are closely related to the increase in osmolar pressure of blood plasma, permeability of erythrocyte membranes for sodium ions, and hemolysis (low resistance of red blood cells, increased indirect bilirubin), and hepatocytes (increase of direct bilirubin). On the background of the targeted antihypertensive therapy the severity of the processes is low and nearly similar to those in healthy persons of corresponding temperament that is the evidence of high efficiency of targeted treatment option.

ERYTHROCYTE CATIONS IN THE ADAPTATION PROCESS IN PERCH PERCA FLUVIATILIS L. (PERCIDAE)

The concentration of sodium and potassium ions in erythrocytes in perch Perca fluviatilis L. was compared to that in ten other freshwater fish species. The cation concentration was determined by flame photometry. The participation of erythrocyte cations in the buffer and respiratory processes that promote the specific resistance of perch to unfavorable factors is substantiated. Among the investigated fish species, the highest sodium concentrations in red blood cells were found in perch and pike, who are the most resistant to water acidification. High sodium concentration in red blood cells indicates a high alkalization capacity of the erythrocytes’ inner environment and is one of the mechanisms for enhanced resistance of perch to water acidification. In perch the potassium concentration in erythrocytes is at the lower limit of the range typical for fish resistant to hypoxia. A high potassium level in red blood cells is regarded as one of the mechanisms for promoting the tolerance of perch to hypoxia. Analysis of data from the literature revealed the same kind of participation of erythrocyte sodium in buffer processes and erythrocyte potassium in respiratory processes in marine fish as in freshwater fish. When determining the level of hematocrit, higher values of this parameter were found in perch as compared to other freshwater fish. Other known physiological and biochemical mechanisms for promoting total and specific resistance of perch to detrimental factors are also analyzed in the paper.

Concentration of Potassium in Plasma, Erythrocytes, and Muscle Tissue in Cows with Decreased Feed Intake and Gastrointestinal Ileus.

BackgroundHealthy cows consume large amounts of potassium and a sudden loss in appetite can lead to hypokalemia. The routine method to evaluate potassium homeostasis is the measurement of the extracellular potassium in plasma or serum, but this does not provide information about the intracellular potassium pool.Hypothesis/ObjectivesTo evaluate potassium homeostasis by comparing the extracellular and intracellular potassium concentration in cows with reduced feed intake and gastrointestinal ileus.AnimalsTwenty cows 1–3 days postpartum (group 1) and 20 cows with gastrointestinal ileus (group 2).MethodsObservational cross‐sectional study. Plasma potassium was measured by using an ion‐sensitive electrode. Intracellular potassium was measured in erythrocytes and muscle tissue (muscle biopsy) by using inductively coupled plasma optical emission spectroscopy.ResultsCows of group 1 did not have hypokalemia. Overall cows with gastrointestinal ileus were hypokalemic (mean ± SD, 2.9 mmol/L ± 0.78), but potassium concentration in erythrocytes and muscle tissue was not lower than in postpartum cows. Intracellular potassium in erythrocytes varied very widely; group 1: 3497–10735 mg/kg (5559 ± 2002 mg/kg), group 2: 4139–21678 mg/kg (7473 ± 4034 mg/kg). Potassium in muscle tissue did not differ between group 1 (3356 ± 735 mg/kg wet weight) and group 2 (3407 ± 1069 mg/kg wet weight). No association between extracellular and intracellular potassium concentrations was detected.Conclusions and clinical importanceThat measurement of plasma potassium concentration is not sufficient to evaluate potassium metabolism of cows.

Effects and Mechanisms of Action of Polyene Macrolide Antibiotic Nystatin on Babesia gibsoni In Vitro

Nystatin is a membrane-active polyene macrolide antibiotic and a channel-forming ionophore. Nystatin exhibits in vitro activity against Babesia gibsoni infecting normal canine erythrocytes containing low potassium (LK) and high sodium concentrations, i.e., LK erythrocytes. The calculated IC(50) value of nystatin against B. gibsoni infecting LK erythrocytes was 31.96 µg/ml. The anti-babesial activity of nystatin disappeared when B. gibsoni in LK erythrocytes were incubated in culture media containing high potassium concentrations (HK). Moreover, when the parasites were harbored in canine HK erythrocytes, which contained high potassium and low sodium concentrations as a result of high Na-K-ATPase activity, the in vitro anti-babesial activities of nystatin also disappeared, apparently due to protection by HK erythrocytes. This suggested that nystatin could show in vitro anti-babesial activity against B. gibsoni by its ionophorous activity, the same as other ionophores such as valinomycin. Subsequently, the effects of nystatin on the host cells were observed. Nystatin could not modify the intracellular concentrations of potassium, sodium, adenosine triphosphate, or glucose in either LK or HK erythrocytes, although it caused weak hemolysis in HK erythrocytes. In addition, nystatin did not affect the survival of canine peripheral polymorphonuclear leukocytes. In conclusion, nystatin destroyed B. gibsoni by ionophorous activity but did not affect either canine erythrocytes or leukocytes in vitro.

Biochemical polymorphism of erythrocyte potassium and glutathione protein: the relationship with some blood parameters in Kivircik sheep breed.

This paper aims to search genetic structures of purebred Kivircik sheep raised in Turkey based on erythrocyte potassium and glutathione types and also to determine the relationship between these components and some blood parameters. The phenotypic frequencies were 68% for LK and 32% for HK erythrocyte potassium types in the purebred Kivircik breed. The allele gene frequency of KH and KL loci were calculated as 0.56 and 0.44 respectively. There was no relationship detected between gender factor and blood parameters. But, significant relationships were obtained between erythrocyte potassium types and some blood parameters (Nawb, Nae, Kwb, Kp, Ke, Nae +Ke; p<0, 05). At the same time, the correlation coefficient between Ke and Nae was calculated as R = -0.58, (p<0.01). But, correlation coefficient was not significant between blood parameters and hematocrit value (PCV). All animals were detected as low types in terms of glutathione level (GSHh). The mean of erythrocyte glutathione was determined as 29.79 mg/dL in red blood cell. The mean of erythrocyte potassium concentrations (Ke) were 9.22 and 23.47 mmol/L for the LK and HK types of animals, respectively and the mean differences between LK and HK types were statistically important in this study (p<0.01). Key words: Kivircik sheep, erythrocyte potassium, glutathione, blood polymorphism.

Erythrocyte potassium, sodium and glutathione concentrations and their relationship with reproduction, body weight and fleece weight traits in Awassi sheep

Abstract. Relationship between erythrocyte potassium (Ke), erythrocyte sodium (Nae) and blood glutathione (GSH) concentrations and production/ reproduction traits were investigated in Awassi sheep. Thirty healthy sheep subjected to analyze for phenotypic and gene frequencies of Ke, Nae and GSH concentrations. Correlation between these parameters and production/ reproduction traits such as greasy fleece weight, milk production, birth rate, single and twin birth rate and body weight were calculated. A positive correlation was found between birth rate and mean Ke concentration (r=0.481, P&lt;0.008) and Nae concentration (r=−0.454, P&lt;0.013). Another correlation between GSH concentration and greasy fleece weight (r=−0.368, P&lt;0.049) and milk production (r=0.379, P&lt;0.050) parameters was also evidenced. These suggest that Ke, Nae and GSH concentrations may be included in the metabolic profile testing parameters.

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

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Predictors of blood pressure and left ventricular mass in the young: the Hypertension in Pregnancy Offspring Study.

The present study evaluates potential predictors for the future blood pressure and left ventricular mass in children. Fifty-two children were studied at mean age 12.6 +/- 1.5 years and reexamined after 5.6 years. Thirty-six children were born to mothers who had hypertension during pregnancy and 16 children were born after normotensive pregnancies by mothers who remained normotensive at follow-up. Blood pressure was measured at rest and during physical exercise. Left ventricular mass was calculated from M-mode echocardiography, and erythrocyte sodium and potassium concentrations were determined. A stepwise multiple linear regression analysis was used to predict subsequent blood pressure and left ventricular mass. Final systolic blood pressure was best explained by initial systolic blood pressure, erythrocyte potassium concentration, gender, and erythrocyte sodium concentration. Final diastolic blood pressure was best explained by erythrocyte potassium concentration. Gender and initial left ventricular mass were predictors of left ventricular mass at follow-up. This prospective study corroborates previous findings that blood pressure measured in children predicts their future blood pressure. Furthermore, an independent inverse relationship between childhood erythrocyte potassium concentration and adolescent blood pressure is demonstrated. Male gender and an early increased left ventricular mass are independent predictors of an increased left ventricular mass in adolescents.

Potassium concentrations in muscle, plasma and erythrocytes and urinary fractional excretion in normal horses and those with chronic intermittent exercise-associated rhabdomyolysis

Potassium concentrations were measured in semimembranosus muscle, plasma and erythrocytes, and the urinary fractional excretion determined in normal horses and those that had chronic intermittent exercise-associated rhabdomyolysis. Muscle from the rhabdomyolysis horses was also evaluated microscopically. The horses with rhabdomyolysis had a lower muscle potassium concentration on a dry weight basis. Although the wet weight potassium content was also lower, the difference was not significant. Urinary fractional excretion of potassium (and also sodium and chloride) did not differ significantly between the two groups although the rhabdomyolysis group had a lower percentage excretion of potassium. Erythrocyte potassium concentration was similar for both groups. Low grade to moderate degenerative myopathy or absence of lesions was seen on microscopic sections of muscle from horses with rhabdomyolysis; only one had a vacuolar myopathy and potassium content was not determined. These results suggest that altered muscle potassium content may be a factor in rhabdomyolysis.

Decreased erythrocyte Na +, K +-ATPase activity associated with cellular potassium loss in extremely low birth weight infants with nonoliguric hyperkalemia

To determine whether a shift of potassium ions from the intracellular space to the extracellular space accounts, in part, for the hyperkalemia seen in extremely low birth weight infants, we examined potassium concentration in serum and erythrocytes from extremely low birth weight infants with hyperkalemia (n = 12) or with normokalemia (n = 27). In addition, to determine whether the shift of potassium was associated with low sodium-potassium-adenosinetriphosphatase (Na+,K(+)-ATPase) activity, we studied the activity of ATPase in the last 16 infants enrolled in the study. Fluid intake and output were measured during the first 3 days of life. Infants were considered to have hyperkalemia if the serum potassium concentration was 6.8 mmol/L or greater. Blood was obtained daily for intracellular sodium and potassium levels by means of lysis of erythrocytes. The remaining erythrocyte membranes were frozen and analyzed for Na+,K(+)-ATPase activity. There were significantly lower intracellular potassium/serum potassium ratios in the infants with hyperkalemia for each day of the 3-day study (p < 0.001). In the hyperkalemic group, there was lower Na+,K(+)-ATPase activity than in the infants with normokalemia (p = 0.006). Low Na+,K(+)-ATPase activity was associated with lower intracellular potassium/serum potassium ratios (p = 0.006), higher serum potassium values (p = 0.02), and lower intracellular potassium concentration (p = 0.009). The urinary data demonstrated that there was no difference in glomerulotubular balance between the two groups. We conclude that nonoliguric hyperkalemia in extremely low birth weight infants may be due, in part, to a shift of potassium from the intracellular space to the extracellular space associated with a decrease in Na+,K(+)-ATPase activity.

Relationship between cellular ATP, potassium, sodium and magnesium concentrations in mammalian and avian erythrocytes

Intracellular K + Na + ratios of erythrocytes of various mammalian species are known to differ markedly. We have measured ATP, K +, Na +, Mg 2+, H 2O contents of erythrocytes of twelve mammalian and three avian species. Our results indicate that the intracellular ATP concentration in erythrocytes of different species is in close positive correlation with the K + Na + ratios (linear correlation coefficient, r = 0.852). Furthermore, ATP levels in erythrocytes of individual sheep with different potassium concentrations correspond with their K + Na + ratios ( r = 0.747). Intracellular magnesium concentrations also correlate with ATP concentrations in erythrocytes of different species ( r = 0.629) and in different sheep ( r = 0.549).

Furosemide-induced electrolyte depletion associated with echinocytosis in horses

SUMMARY Echinocytes have been incriminated in the pathogenesis of exertional diseases in horses. To evaluate the hypothesis that echinocytes are dehydrated erythrocytes, we decreased blood sodium and potassium concentrations in 4 horses by administering furosemide (1.0 mg/kg of body weight, q 12 h) for 2 days and we monitored cbc, serum and erythrocyte sodium and potassium concentrations, and echinocyte numbers. Serum sodium concentration decreased progressively over the 48 hours of furosemide administration, then returned to near baseline concentration at 168 hours. A statistically significant decrease (P &lt; 0.05) in serum potassium concentration was observed at 24, 48, and 72 hours after initial furosemide administration, and remained less than the baseline value at the end of the study. Mean erythrocyte potassium concentration decreased rapidly and remained low at the end of the study. Minimal changes were observed in erythrocyte sodium concentration during the first 72 hours after furosemide administration, but the value was significantly (P &lt; 0.05) increased at 168 hours. Type-I and type-II echinocyte numbers increased by 4 hours after furosemide administration and persisted throughout the study. Type-III echinocytes were not seen in baseline samples, but numbers increased only modestly after furosemide administration. Administration of epinephrine to well-hydrated horses increased echinocyte numbers only minimally, indicating that splenic contraction was not the likely cause for the furosemide-associated increase. To determine whether the decrease in erythrocyte potassium concentration and increase in sodium concentration was caused by furosemide acting directly on the erythrocyte membrane, we quantified erythrocyte potassium and sodium concentrations before and after incubation with furosemide in vitro. Incubation of erythrocytes with furosemide failed to induce depletion of erythrocyte potassium concentration or to increase erythrocyte sodium concentration. These data support the hypothesis that echinocytes are dehydrated cells and that these changes are induced by total body cation depletion.

The effects of hypocalcaemia due to a 4-hour infusion of Na 2EDTA solution on various blood and urine analytes in dairy cows and a comparison of these effects between cows with high and low erythrocyte potassium concentrations

Six HK (high erythrocyte potassium) and 7 LK (low erythrocyte potassium) dairy cows were subjected to a 4-h intravenous infusion of 4.7% Na 2EDTA solution to induce and maintain hypocalcaemia. Blood samples taken immediately before infusion, hourly for 7 h, and at 24 h after commencement of infusion were subjected to determination of concentration (or count) of 16 analytes. The mean changes in concentrations (or counts) of the various blood analytes were calculated for the periods 0–4, 4–7, 7–24, and 0–24 h after commencement of the infusion for all cows combined, and then separately for the HK and LK groups of cows. Plasma Ca(PCa), plasma inorganic phosphorus (PiP) and plasma potassium (PK) showed significant decreases during the 4-h infusion period and were still below pretreatment levels 24 h later. AST, CPK, PCVs and white cell counts (WCCs) showed significant early increases which were still significantly elevated 24 h later. Plasma magnesium (PMg) and erythrocyte Na(ENa) and K(EK) all showed delayed changes which still persisted 24 h later. Significant between-group differences were present for PCVs which increased significantly more in the LK than the HK group during the infusion period, for PCa which showed a greater increase in the HK cows than the LK cows during the 4–7 h early clinical recovery period, and for plasma bilirubin (PBil) which showed a greater increase from 0 to 24 h in the HK group than in the LK group. Urine samples, collected before infusion, 4–7 h and 24 h after commencement of the infusion, were subjected to analysis for glucose, protein, pH, ‘blood’ and ketones. Most cows showed increases in urinary glucose, protein and ‘blood’.

Changes in Blood Pressure, Plasma Triglyceride and Aldosterone Concentration, and Red Cell Cation Concentration in Patients With Hyperinsulinemia

Blood pressure, plasma concentration of triglyceride, aldosterone, renin activity (PRA), and atrial naturietic peptide (ANP), and red blood cell, urine, and plasma sodium and potassium concentration were determined in 24 healthy individuals divided into two groups defined as being either hyperinsulinemic or normoinsulinemic. The results demonstrated that the hyperinsulinemic group had significantly higher values for both systolic (P less than .01) and diastolic (P less than .05) blood pressure. In addition, plasma concentrations of triglyceride (P less than .02), aldosterone (P less than .05) and potassium (P less than .05) were higher in hyperinsulinemic individuals as compared to those who were normoinsulinemic. Furthermore, red cell potassium was lower (P less than .01) and red cell sodium higher (P less than .01) in the hyperinsulinemic group. Finally, the magnitude of hyperinsulinemia correlated directly with systolic (r = 0.50, P less than .01) and diastolic (r = 0.44, P less than .05) blood pressure, concentration of plasma triglyceride (r = 0.55, P less than .01) and aldosterone (r = 0.46, p less than .05), and erythrocyte sodium concentration (r = 0.57, p less than .01). In contrast, plasma insulin response was negatively correlated with erythrocyte potassium concentration (r = 0.40, P less than 0.05). These observations provide further support for the view that hyperinsulinemia, presumably secondary to resistance to insulin-stimulated glucose uptake, is associated with a cluster of variables that may play important roles in the etiology and clinical course of hypertension.

Effect of whole-body potassium depletion on plasma, erythrocyte, and middle gluteal muscle potassium concentration of healthy, adult horses

SUMMARY The effects of whole-body potassium depletion induced by food deprivation on plasma, erythrocyte, and middle gluteal muscle K concentrations was quantified in 16 healthy, adult horses before, during, and at the end of a 7-day period of food deprivation during which water and sodium chloride were available ad libitum. Potassium concentrations were determined by atomic absorption spectroscopy. Plasma K concentration remained constant (3.49 ± 0.09 mM K/L of plasma; mean ± sem) throughout the study. Erythrocyte potassium concentration decreased from 93.10 ± 1.94 mM K/L of erythrocytes on day 0 to 88.63 ± 2.39 mM K/L of erythrocytes on day 2 (decrease of 4.8%; P &lt; 0.05) and thereafter did not change. The K concentration of the middle gluteal muscle decreased from 91.06 ± 2.96 μM K/g of muscle (wet weight) to 79.61 ± 2.09 μM K/g of muscle (decrease of 12.6%; P &lt; 0.05) on day 4 and decreased further on day 7 to 73.62 ± 1.85 μM K/g of muscle (decrease of 19.2%; P &lt; 0.05). There was no correlation between the plasma and erythrocyte K concentrations (r = −0.066), the erythrocyte and middle gluteal muscle K concentrations (r = 0.167), or the plasma and middle gluteal muscle potassium concentrations (r = −0.018). The water content of the middle gluteal muscle remained constant (73.23 ± 0.36%) throughout the study. Erythrocyte membrane potential did not change (−99.26 ± 0.87 mV) during the study, whereas the magnitude of the membrane potential of the middle gluteal muscle decreased from −105.84 ± 1.67 mV on day 0 to −100.93 ± 2.10 mV on day 7 (P &lt; 0.05).

Membrane ATPase, erythrocyte sodium and potassium in haemodialysis patients.

This study was undertaken to evaluate the effect of chronic renal failure as well as dialysate sodium concentration during haemodialysis on membrane ATPase activity and erythrocyte sodium and potassium concentration. Intracellular Na and K were not changed in patients when compared to normal subjects. There was, however, a significant decrease of Na-K-ATPase activity in patients versus controls. Erythrocyte sodium increased during haemodialysis with low and normal sodium dialysate. The present results suggest that sodium dialysate concentration has an influence on the intracellular cationic homeostasis.

Interactions Between ion Exchange and Metabolism in Erythrocytes of the Rainbow TroutOncorhynchus Mykiss

ABSTRACTExperiments were carried out to investigate the relationship between ion exchange and energy metabolism in rainbow trout erythrocytes in vitro. Under resting conditions, the sodium/potassium pump accounts for 20% of the cellular energy budget. In the presence of the β-adrenergic agonist isoproterenol, however, this increases to 43%. Inhibition of the sodium/potassium pump with ouabain results in greater increases in erythrocyte water content and sodium and chloride concentrations and a greater decrease in erythrocyte potassium concentration following stimulation by isoproterenol. Moreover, the decrease in erythrocyte NTP levels observed following adrenergic stimulation does not occur when the sodium/potassium pump is inhibited with ouabain. Inhibition of the sodium/ potassium pump also abolishes the increase in oxygen consumption by the cells which normally takes place following adrenergic stimulation. Finally, depletion of erythrocyte NTP levels by the sodium ionophore monensin or by previous incubation with nitrogen does not result in a significant increase in oxygen consumption. Thus, catecholamines appear to be crucial for the metabolic-membrane coupling that occurs following adrenergic stimulation in rainbow trout erythrocytes.

Decreased erythrocyte potassium concentration associated with exercise-related myopathy in horses

Summary To investigate the possibility that a disorder of potassium balance may have a role in the development of equine rhabdomyolysis, the potassium concentration within erythrocytes (RBC [K+]) and plasma (P [K+]) was measured in 3 groups of horses: group 1, eight 2-year-old fillies that had postexercise muscle soreness within 48 hours of sample collection; group 2, ten 2-year-old fillies subjected to identical management and training conditions (as fillies of group 1) and that did not have signs of myopathy; and group 3, 32 yearlings of both sexes on the farm of origin of groups 1 and 2 that were pastured and not in training. Creatine kinase activity in serum from horses of groups 1 and 2 was also measured. The mean P [K+] was not significantly different between groups, whereas the mean RBC [K+] was significantly (P &lt; 0.01) lower in group-1 fillies vs group-2 fillies and group -3 horses. Group-1 fillies also had markedly high serum creatine kinase activity. Results of the study revealed significantly lower RBC [K+] in horses that had had signs of myopathy within the preceding 48 hours. This does not prove a causal relationship between RBC potassium depletion and myopathy, but does suggest that decreased RBC [K+] may be observed in horses with exercise-related myopathy.

A Comparison Between the Main Clinical Signs of Milk Fever in Cows with Those of Hypocalcaemia Induced by Na2EDTA Solution

In one study, 6 cows with high erythrocyte potassium concentrations (HK cows) and 7 with low erythrocyte potassium concentrations (LK cows) were infused with 4.7% Na2EDTA solution intravenously for 4 h. The immediately observable clinical signs and the sequelae over a period of weeks were recorded and compared. There were no differences in the clinical responses of HK or LK cows to the infusion of Na2EDTA. In a second study, these clinical signs plus those produced experimentally by three other research groups were compared with both the clinical signs of milk fever recorded in three text books and those observed by one of the authors over a period of 25 years in dairy cattle practice. All of the clinical signs of milk fever occurred in the experimental model, but there were extra signs (excessive salivation, excessive lip and tongue actions, and tail lifting) which were not present or recorded in naturally occurring cases of hypocalcaemia. Hypocalcaemia induced in cows by the intravenous infusion of 4.7% Na2EDTA solution is a reasonably good model for the reproduction of the clinical signs of milk fever, but because of the extraneous signs, and the unusual nature of the subsequent deaths of 3 of 13 cows infused for 4 h, and the death of 1 of 2 cows infused for 4 h daily for 3 days, the model may not be a valid one for periods longer than 4 h in cows.