The plasma membrane composition affects intracellular processes and the cellular susceptibility to free radical attack, which has been associated with the impairment of cellular functions occurring during senescence.

The study of the modifications of the plasma membrane in centenarians might elucidate the biological mechanisms at the basis of longevity and successful aging. The work was performed in 190 subjects, divided into five groups according to the age range: (1) 21-40 years (n=25); (2) 41-60 years (n=30); (3) 61-80 years (n=30); (4) 81-99 years (n=50); and (5) centenarians (> or = 100 years) (n=55).

The following determinations were performed on erythrocyte membranes:
(i) the lipid peroxide level (Lp) evaluated as malondialdehyde content;
(ii) susceptibility to in vitro oxidation evaluated as difference in the content of thiobarbituric acid-reactive substances before and after phenylhydrazine addition;
(iii) unsaturated/saturated fatty acid ratio and individual polyunsaturated fatty acid composition measured by gas chromatography; and
(iv) fluidity studied by means of the anisotropy of the probe 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH).

Erythrocyte membranes from centenarians showed:
(i) decreased basal lipid peroxide levels and reduced susceptibility to peroxidation in comparison with elderly subjects;
(ii) increased unsaturated/saturated fatty acid ratio in comparison with every other age group;
(iii) higher levels of eicosapentaenoic and docosahexaenoic acid and reduced content of linoleic and arachidonic acid in comparison with elderly subjects; and
(iv) decreased anisotropy of TMA-DPH, i.e. higher fluidity compared with all the other age groups.

In conclusion, the present work demonstrates that erythrocyte membranes from centenarians show some distinct features in comparison with elderly subjects that might act in a protective way against injuries.