Pannexin 1 channels control the hemodynamic response to hypoxia by regulating O-sensitive extracellular ATP in blood.

Pannexin 1 (Panx1) channels export ATP and may contribute to increased concentration of the vasodilator ATP in plasma during hypoxia in vivo. We hypothesized that Panx1 channels and associated ATP export contribute to hypoxic vasodilation, a mechanism that facilitates the matching of oxygen delivery to metabolic demand of tissue. Male and female mice devoid of Panx1 () and wild-type controls (WT) were anesthetized, mechanically ventilated, and instrumented with a carotid artery catheter or femoral artery flow transducer for hemodynamic and plasma ATP monitoring during inhalation of 21% (normoxia) or 10% oxygen (hypoxia). ATP export from WT vs. erythrocytes (RBC) was determined ex vivo via tonometer experimentation across progressive deoxygenation. Mean arterial pressure (MAP) was similar in ( = 6) and WT ( = 6) mice in normoxia, but the decrease in MAP in hypoxia seen in WT was attenuated in mice (-16 ± 9% vs. -2 ± 8%; < 0.05). Hindlimb blood flow (HBF) was significantly lower in ( = 6) vs. WT ( = 6) basally, and increased in WT but not mice during hypoxia (8 ± 6% vs. -10 ± 13%; < 0.05). Estimation of hindlimb vascular conductance using data from the MAP and HBF experiments showed an average response of 28% for WT vs. -9% for mice. Mean venous plasma ATP during hypoxia was 57% lower in ( = 6) vs. WT mice ( = 6; < 0.05). Mean hypoxia-induced ATP export from RBCs from mice ( = 8) was 82% lower than that from WT ( = 8; < 0.05). Panx1 channels participate in hemodynamic responses consistent with hypoxic vasodilation by regulating hypoxia-sensitive extracellular ATP levels in blood. Export of vasodilator ATP from red blood cells requires pannexin 1. Blood plasma ATP elevations in response to hypoxia in mice require pannexin 1. Hemodynamic responses to hypoxia are accompanied by increased plasma ATP in mice in vivo and require pannexin 1.