High erythrocyte membrane (Na+ + K+)-ATPase in kwashiorkor, in vivo reversal by diuretic

Malnutrition causes a reduction in alveolar epithelial sodium and chloride transport which predisposes to death from lung injury

BACKGROUND

All forms of malnutrition have been associated with increased severity of pneumonia, an increased pneumonia associated mortality and an increased risk of pulmonary fluid overload. Malnutrition was found to be associated with increased sweat sodium and chloride concentrations. A reduction of systemic sodium and chloride transport reflected in sweat sodium and chloride levels has been linked to increased severity of pulmonary edema in children with septicemia.

HYPOTHESIS

Malnutrition causes a reduction in alveolar epithelial sodium and chloride transport which predisposes to death from lung injury. SUPPORTING EVIDENCE FOR THE HYPOTHESIS: Malnutrition caused reduced pulmonary fluid clearance in the rat model. Amiloride insensitive pulmonary fluid clearance in malnourished rats was reduced. The reduction in fluid clearance was reversible by beta agonists which increases epithelial sodium and chloride transport.

IMPLICATIONS OF THE HYPOTHESIS

Reduction of alveolar ion and fluid transport capacity explains the predisposition to death from pulmonary edema associated with intravenous fluids and blood transfusions in inpatients with malnutrition. Reduced alveolar epithelial ion transport impairs absorption of intra-alveolar inflammatory exudate in pneumonia leading to a increased severity of respiratory compromise and increased mortality. MEANS TO TEST THE HYPOTHESIS: Nasal potential difference measurements could compare airway epithelial sodium and chloride transport in patients with and without malnutrition and malnutrition associated lung disease. Sweat sodium and chloride concentrations could be compared in patients with and without respiratory disease associated with malnutrition and correlated with the severity of respiratory compromise.

Kidney mitochondrial respiration in protein- and energy-malnourished rats

Several lines of evidence show a close association between plasma membrane Na,K-ATPase and mitochondrial respiration. Extending the observation in human erythrocyte membrane (6), Na,K-ATPase activity has been shown to be elevated in kidney microsomal preparations from protein- and energy-malnourished rats (10). Kidney mitochondrial respiration was studied in these rats under various conditions of assay. Sucrose was used as a modifier of mitochondrial morphology and volume to study its effect on these mitochondria. Mitochondrial state 3 respiration was increased by 35% in protein-deficient rats (P less than 0.02). Vmax(ADP) of state 3 respiration was increased by about 47% in protein- as well as energy-restricted rats. Mitochondria from protein- and energy-deficient rats were more tightly coupled as compared to those from control group. Km apparent for (ADP) and (Pi) were elevated in protein- and energy-malnourished rats. The magnitude of increase was much more in energy-deficient rats. Morphological differences between the mitochondria from two dietary manipulations were reflected in differences in the responses of state 3 respiration, Km(ADP), state 4 respiration, and respiratory control ratios to changing sucrose concentrations. This increase in mitochondrial respiration parallels the increased Na,K-ATPase activity in these rats. Increased Km (ADP and Pi) for mitochondrial respiration are perhaps in response to increased availability of these metabolites in the cytosol. The sucrose effect, in addition, distinguishes the morphological differences in mitochondrial membrane due to protein or energy deficiencies. In conclusion, these results, to a great extent, support an association between the activity of Na,K-ATPase and mitochondrial respiration. The study of mechanism(s) which could contribute to the enhancement of mitochondrial respiration will be of general importance to the understanding of regulation of mitochondrial oxidative phosphorylation, and is of particular interest to us.

[3H]Ouabain binding to human erythrocytes in protein-énergy malnutrition

[3H]Ouabain binding to erythrocytes was determined in normal children and in children suffering from kwashiorkor or marasmus. Scatchard plot analysis of [3H]ouabain binding displayed straight lines with linear slopes in all subjects indicating the presence of a single species of ouabain binding sites on erythrocytes. The number of ouabain binding sites per cell was 385 +/- 26 (mean +/- SEM, n = 3) in normal, 891 +/- 102 (n = 8) (p less than 0.001) in kwashiorkor and 316 +/- 45 (n = 3) in marasmic children. The equilibrium dissociation constant (Kd) for ouabain binding in kwashiorkor (16 nmol/1) was similar to that in control (12 nmol/1). The specific activity of Na+, K+ -ATPase of erythrocyte membrane has been shown to be higher in kwashiorkor children as compared to normal children [3]. This increase in enzyme activity may be considered as a consequence of increase in the enzyme content as indicated by the increased number of ouabain binding sites on red cells. Elevation in the level and activity of erythrocyte Na+, K+ -ATPase in kwashiorkor might represent a compensatory mechanism in response to a primary membrane abnormality, to effect prevention of Na+ accumulation and K+ depletion inside the cell.

A study of erythrocyte membrane cation transport adenosine triphosphatases in pregnancy-induced hypertension and of in vivo effects of diuretic treatment

Plasma and erythrocyte Na+ and K+ and erythrocyte membrane (EM) Na+, K+ ATPase, Mg2+ ATPase and Ca2+, Mg2+ Atpase activities were studied in four groups of women -- non-pregnant, normal pregnant, with pregnancy edema (PE) and with pregnancy induced hypertension (PIH). The effect of diuretic therapy in PE and PIH was also evaluated. Plasma Na+ concentration was higher in PE and PIH. There was a significant reduction in (Na+ + K+) ratio between cell and plasma in these two groups. EM Na+, K+ ATPase was unaltered in PE and PIH. The Mg2+ ATPase was elevated by 44% in PE and by 100% in PIH subjects. There was a 50% reduction in Ca2+, Mg2+ ATPase activity in PE. Diuretic therapy had no effect either on electrolyte levels or on any of the EM ATPases. From these results it may be concluded that Na, K, ATPase -- which in kidney is a site of action for furosemide, a potent diuretic -- is unaffected in PE and PIH and, hence, treatment with diuretics -- is unaffected in PE and PIH and, hence, treatment with diuretics in such patients may be ineffective.