O2 permeability of lipid bilayers is low, but increases with membrane cholesterol.
Cell Mol Life Sci
; 78(23): 7649-7662, 2021 Dec.
Article
in En
| MEDLINE
| ID: mdl-34694438
ABSTRACT
Oxygen on its transport route from lung to tissue mitochondria has to cross several cell membranes. The permeability value of membranes for O2 (PO2), although of fundamental importance, is controversial. Previous studies by mostly indirect methods diverge between 0.6 and 125 cm/s. Here, we use a most direct approach by observing transmembrane O2 fluxes out of 100 nm liposomes at defined transmembrane O2 gradients in a stopped-flow system. Due to the small size of the liposomes intra- as well as extraliposomal diffusion processes do not affect the overall kinetics of the O2 release process. We find, for cholesterol-free liposomes, the unexpectedly low PO2 value of 0.03 cm/s at 35 °C. This PO2 would present a serious obstacle to O2 entering or leaving the erythrocyte. Cholesterol turns out to be a novel major modifier of PO2, able to increase PO2 by an order of magnitude. With a membrane cholesterol of 45 mol% as it occurs in erythrocytes, PO2 rises to 0.2 cm/s at 35 °C. This PO2 is just sufficient to ensure complete O2 loading during passage of erythrocytes through the lung's capillary bed under the conditions of rest as well as maximal exercise.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Oxygen
/
Oxygen Consumption
/
Cell Membrane Permeability
/
Cholesterol
/
Erythrocytes
/
Lipid Bilayers
Limits:
Humans
Language:
En
Journal:
Cell Mol Life Sci
Journal subject:
BIOLOGIA MOLECULAR
Year:
2021
Document type:
Article
Affiliation country:
Germany