Postasphyxial reoxygenation reduces the activity of Na+/K+-ATPase in the erythrocytes of newborn piglets

The impairment of the Na⁺/K⁺-pump might play a role in the pathomechanism of cell swelling in hypoxia induced brain damage. The effect of acute hypoxia on erythrocyte Na⁺/K⁺-ATPase activity, intracellular electrolyte and ATP([Na⁺]_ic,[K⁺]_ic,[ATP]_ic) contents was studied in ten newborn piglets. Bilateral pneumothorax (PTX) was induced for 60 minutes. Na⁺/K⁺-ATPase activity,[Na⁺]_ic,[K⁺]_ic and [ATP]_ic were measured in baseline condition (mean±SEM: p_aO₂: 60.4±3.1 mmHg); in the 60^th min. of the experiment (p_aO₂: 30.2±2.4, p<0.001); then, after relieving PTX and resuscitating the animals, in the 120^th, 180^th, 240^th min. (54.8±3, 56.1±2.9, 57.2±3.2).

The Na⁺/K⁺-ATPase activity was reduced on the 240^th min. (676±56 vs 833±47 nmolATP/mg prot^*h^-1, p<0.05). The [Na⁺]_ic was lower in the 60^th and 120^th min, but later it has become normal. The [ATP]_ic was higher in the 240^th min.

Our results indicate that during posthypoxic reoxygenation the activity of Na⁺/K⁺-ATPase of RBCs decreases in newborn piglets. As a result the [ATP]_ic increased. The [Na⁺]_ic and[K⁺]_ic do not reflect the alteration of enzyme activity. Measuring of Na⁺/K⁺-ATPase activity on RBCs may be a diagnostic help in detecting hypoxic damage in newborn human subjects.