Abstract
RBCs release ATP when exposed to low O2 tension (pO2) or in response to receptor‐mediated activation of the prostacyclin (PGI2) receptor. The mechanism by which ATP, a highly charged anion, exits the RBC remains controversial. RBCs do not form vesicles; therefore, ATP must exit the membrane through a channel or transporter. It was reported that PANX1, a gap junction protein capable of forming an ATP‐permeable channel in plasma membranes, is present in human RBCs and that inhibiting PANX1 with carbenoxolone (CBX) reduced ATP release from RBCs stimulated by hypotonic stress. Here we studied the role of PANX1 in two independent ATP release signaling pathways using isolated human RBCs. Cells were exposed to either low pO2 (9.1 ± 0.6 mmHg) in a tonometer or the PGI2 analog, iloprost (ILO, 1 μM). ATP release was measured in the presence and absence of one of three PANX1 inhibitors (CBX (100 μM), probenecid (PB, 100 μM), and 10panx1 peptide (10PANX, 200 μM)). CBX, PB, and 10PANX reduced ATP release in response to lowered pO2 by 92.1 ± 29.9% (n=7, p<0.05), 91.8 ± 18.0% (n=5, p<0.05), and 90.9 ± 15.5% (n=5, p<0.01), respectively. In contrast, CBX (n=6), PB (n=3), and 10PANX (n=1) did not reduce ILO‐induced ATP release. These results provide strong support for the hypothesis that PANX1 is the ATP conduit for low pO2‐induced ATP release but not ILO‐induced ATP release from human RBCs. [Supported by NIH grants HL‐64180 and HL‐89094].
Published Version
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