Abnormalities of sodium transport by sodium, potassium-activated adenosine triphosphatase in erythrocytes from obese children

1. Intracellular Na⁺ concentration [Na⁺](i) and Na⁺ extrusion catalysed by sodium, potassium-activated adenosine triphosphatase (Na⁺, K⁺-pump) were evaluated in erythrocytes from 21 obese children and 20 normal weight- and age-matched controls. 2. Obese children showed a significantly decreased V(max.) for Na⁺, K⁺-pump-matched Na⁺ efflux (5638 ± 338 vs 7579 ± 335 μmol h^-1 litre^-1 of cells mean ± SEM, P = 0.01), while [Na⁺](i) (9.3 ± 0.3 vs 9.1 ± 0.5 mmol/litre of cells, mean ± SEM, NS) and Na⁺ efflux in fresh cells (2380 ± 153 vs 2533 ± 180 μmol h^-1 litre^-1 of cells, mean ± SEM, NS) were similar in both groups. 3. Mean diastolic blood pressure was significantly higher in obese children than in controls, although both groups were normotensive (73.8 ± 1.3 vs 66.2 ± 1.9 mmHg, mean ± SEM, P = 0.009). 4. Abnormal Na⁺, K⁺-pump activity is present in individuals with idiopathic obesity. 5. The possible link between obesity and blood pressure regulation may be mediated through modifications in Na⁺, K⁺-pump activity.