Correlation between human platelet cytoplasmic membrane outer leaflet fluidity, Na+/H+ exchanger activity and aging.

A cross-sectional survey was undertaken to study the aging effect on platelet cytoplasmic membrane outer leaflet fluidity and Na+/H+ antiporter activity, and to investigate the relative influence of membrane order and age on the Na+/H+ exchanger. The study population consisted of 19 healthy subjects (age range 22-83 years, mean age 48.5 +/- 16.5 years; 12 females and 7 males). Washed platelets were used as neuronal models and as eventually contributing to brain pathology by aberrant secretion of their granule content. A significant positive correlation (r = 0.48, p < 0.05) was found between age and the membrane structural order, according to a second-degree equation. Sewall-Wright path coefficient analysis revealed that the age influence on Na+/H+ exchanger activity was unimportant (0.18), but those of cytoplasmic membrane outer leaflet fluidity and mean platelet volume were strong and positive (0.51 and 0.54, respectively). Women presented a marked standard deviation in the countertransporter results. In conclusion, decreased membrane outer leaflet fluidity and unchanged Na+/H+ antiporter activity may contribute to the process of normal brain aging.