Effect of piracetam on Ca 2+ -induced K + efflux from sickle cells

Piracetam has been reported to have a protective rheological effect on sickle cells. When sickle cells were subjected to cyclical oxygenation-deoxygenation for 15 hours in Ca²⁺-containing buffer, there was a loss of cell filterability through pores of 5 µm diameter and an increase in mean cell haemoglobin concentration and percentage irreversibly sickled cells. These changes were consistent with entry of Ca²⁺, activation of the Gardos channel in the sickle cell membrane, and loss of cell K⁺ and water. Piracetam at 100 mmol/l had a significant protective rheological effect. When sickle cells containing ⁸⁶Rb were loaded with Ca²⁺ using the Ca²⁺-ionophore A23187, however, the consequential efflux of K⁺ (⁸⁶Rb) through the Gardos channel was not inhibited by 10 or 100 mmol/l piracetam. The action of piracetam in preventing dehydration of sickle cells would not therefore seem to be due to inhibition of the Gardos channel.