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 Vmax. for Na+, K+-pump-mediated Na+ efflux (5638 +/- 338 vs 7597 +/- 335 mumol 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 mumol 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.