Mechanisms involved in low oxygen tension-induced ATP release from the erythrocyte

The erythrocyte participates in the regulation of its own distribution by releasing the nucleotide adenosine triphosphate (ATP) in response to lowered oxygen (O2) tension. Once released into the vasculature, ATP can bind to purinergic receptors on the vascular endothelium leading to the formation of vasodilators.;The mechanism by which erythrocytes release ATP in response to exposure to lowered O2 tension has long been investigated. A signal transduction pathway that relates exposure of erythrocytes to lowered O2 tension with ATP release has been elucidated and includes the heterotrimeric G protein, Gi. The work presented in this study provides insight into two aspects of the low O2 tension-induced ATP release signal transduction pathway that remain uncharacterized. The two aspects that remain uncharacterized are: (1) the mechanism by which lowered O2 tension activates Gi and (2) the identity of the conduit through which ATP exits the erythrocyte.;In addition to activation by exposure to lowered O2 tension, Gi, in the erythrocyte, can be activated by mechanical deformation. Here we show that erythrocyte membrane deformability is required for low O2 tension-induced ATP release by demonstrating that treating erythrocytes with diamide, a compound known to decrease erythrocyte deformability, attenuates ATP release in response to lowered O2 tension but not in response to direct activation of Gi.;In respect to the identity of the ATP conduit involved in low O 2 tension-induced ATP release, we demonstrate that treating erythrocytes with three pharmacological agents known to inhibit pannexin 1, a protein present in the erythrocyte and known to serve as an ATP conduit in other cell types, prevents ATP release from erythrocytes in response to lowered O2 tension but not in response to receptor mediated activation of Gs (via iloprost). We also demonstrate that, similar to ATP release in response to mechanical deformation, ATP release in response to stimulation with either low O 2 tension or iloprost can be attenuated by treating erythrocytes with glybenclamide, an irreversible inhibitor of the cystic fibrosis transmembrane conductance regulator. The findings presented here provide more insight into the mechanism by which ATP is released from the erythrocyte in response to lowered O2 tension.