Is the mammalian cell plasma membrane a barrier to oxygen transport?

Abstract

Oxygen transport in the Chinese hamster ovary (CHO) plasma membrane has been studied by observing the collision of molecular oxygen with nitroxide radical spin labels placed in the lipid bilayer portion of the membrane at various distances from the membrane surface using the long-pulse saturationrecovery electron spin resonance (ESR) technique. The collision rate was estimated for 5-, 12-, and 16-doxylstearic acids from spin-lattice relaxation times (TI) measured in the presence and absence of molecular oxygen. Profiles of the local oxygen transport parameters across the membrane were obtained showing that the oxygen diffusion-concentration product is lower than in water for all locations at 37°C. From oxygen transport parameter profiles, the membrane oxygen permeability coefficients were estimated according to the procedure developed earlier by Subczynski et al. (Subczynski, W. K., J. S. Hyde, and A. Kusumi. 1989. Proceedings of the National Academy of Sciences, . At 37°C, the oxygen permeability coefficient for the plasma membrane was found to be 42 cm/s, about two times lower than for a water layer of the same thickness as the membrane. The oxygen concentration difference across the CHO plasma membrane at physiological conditions is in the nanomolar range. It is concluded that oxygen permeation across the cell plasma membrane cannot be a rate-limiting step for cellular respiration.Correlations of the form PM = cK~ between membrane permeabilities PM of small nonelectrolyte solutes of mol wt <50, including oxygen, and their partition coefficients K into hexadecane and olive oil are reported. Hexadecane: c = 26 cm/s, s = 0.95; olive oil: c --23 cm/s, s = 1.56. These values ofc and s differ from those reported in the literature for solutes of 50 < mol wt <300 (Walter, A., and J. Gutknecht. 1986. Journal of Membrane Biology. 90:207-217). It is concluded that oxygen permeability through membranes can be reliably predicted from measurement of partition coefficients.

Alkylresorcinols as antioxidants: hydrogen donation and peroxyl radical-scavenging effects

“…Measurements were performed spectrophotometrically at 515 nm following the method of Brand-Williams et al 7 The inhibitory effects of 5-npentadecylresorcinol and a-tocopherol on the autoxidation of puri®ed sun¯ower triacylglycerols were evalunted as described previously. 8 The fatty acid composition of puri®ed sun¯ower triacylglycerols was as follows: palmitic (16:0) 6.4%, stearic (18:0) 22.8±35.9 (CH 2 groups in alkyl chain), 100.4 (C-2), 108.3 (C-4 and C-6), 146.3 (C-5), 156.8 (C-1 and C-3).…”

“…1 Membrane-stabilising effects, involving hydrogen bonding between the hydroxyl groups of ARs and the polar head of the phospholipids and/or hydrophobic interaction between the AR chain and the fatty acid chains, may in¯uence oxygen diffusion in the membrane. 22 It is worth noting that, at high concentrations, ARs were found to impose adverse effects on membrane stability, causing phase separation, reversed micelles or hexagonal phase. 1 It is worth testing whether concentration-dependent membrane stabilising/destabilising effects rather than chemical antioxidation are responsible for the observed cell haemolysis and leakage of ions and small non-electrolytes.…”

The liquid-ordered phase in sphingomyelincholesterol membranes as detected by the discrimination by oxygen transport (DOT) method

“…This saturation-recovery EPR spin-labeling method is able not only to discriminate different membrane domains but also to characterize them by the oxygen transport parameter (oxygen diffusion-concentration product) in situ without the need for physical separation [14,20,21]. The oxygen transport parameter provides useful information about the internal dynamics of each domain [20][21][22][23][24][25][26][27][28]. Knowledge of these properties allows us to assign unknown domains to a certain phase.…”

The aqueous reference for ESR oximetry

“…The use of nitroxide ESR to measure oxygen concentration has provided considerable information about the distribution of oxygen in a variety of heterogeneous biological environments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The method depends on the change in the electron spin relaxation induced in nitroxide radicals by collisional encounters with oxygen.…”