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Aquaporin-1 acts as an O2 channel. The permeability of human and mouse red cell membranes for oxygen
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DOI：10.1152/ajpcell.00858.2024.png)
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Abstract
En 中文
It has been demonstrated that aquaporin-1 (AQP1), one of the most abundant red cell membrane proteins, constitutes a functionally important channel for CO2 in red cell membranes. We ask here, whether AQP1 and other gas channel proteins play a role also in red cell oxygen transport. We use a stopped-flow technique to: 1) compare the oxygen permeability, PO2, of AQP1-deficient (Colton Null) with that of normal human red cell membranes, 2) compare the PO2 of Aqp1(-/-) with that of normal mouse red cells, 3) study the effect of the gas channel inhibitor 4,4 '-diisothiocyanato-2,2 '-stilbenedisulfonate (DIDS) on PO2 of human and mouse red cells, and 4) investigate all three effects at various temperatures between 7 and 37 degrees C, because O-2 transfer across channels and across membrane lipids may depend differently on temperature. We find that at 7 degrees C/10 degrees C lack of AQP1 in the red cell membrane causes significant reductions of PO2, by 20% in human and by 37% in mouse red cells. DIDS causes reductions in PO2 by 34% in human and by 88% in mouse red cells. In addition, the AQP1 inhibitor 5-(phenoxymethyl)furan-2-carbaldehyde (5-PMFC) decreases human red cell PO2 by similar to 40%. All these effects are highly visible at 7 degrees C/10 degrees C, but minor or absent at 25 and 37 degrees C, suggesting that O2 passage through the channel(s) increases less with temperature than O-2 permeation through membrane lipids. Lack of AQP1 and exposure to DIDS or 5-PMFC indicate that AQP1-possibly along with other gas channels-at <25 degrees C acts as an efficient channel for O-2. NEW & NOTEWORTHY Aquaporin-1 is a membrane protein that conducts CO2 at 37 degrees C very efficiently. Here, we show that aquaporin-1 also conducts O-2, but mainly at lower temperatures of around 10 degrees C. Although O-2 transfer across the red cell membrane is accelerated by aquaporin-1 significantly at 10 degrees C, a temperature occurring in poikilotherms, aquaporin-1 apparently does not contribute to O2 passage at 37 degrees C as it occurs in homoiotherms.
Keywords:
aquaporin-1
aquaporin-1-deficient mouse red cells
human Colton null red cells
membrane permeability for oxygen
oxygen channel
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