Relationships between protein carbonyls, retinol and tocopherols level in human plasma.

Free radical oxidation has been claimed as one of the most important mechanism of damage in aging and in several diseases. Carbonyl content in tissue and circulating proteins is a stable marker of this attack. In 29 apparently healthy subjects (25-89 years old) carbonyl content of plasma proteins and retinol and tocopherols (alpha- and gamma-) were studied. Carbonyls level did not show an increase with age. A good correlation between carbonyls content and gamma-tocopherol (r = 0.44, P < 0.05) and a trend with retinol (r = 0.34, P = 0.07) was found, but not with alpha-tocopherol. An inverse correlation was observed between carbonyls and plasma proteins (r = -0.63, P < 0.01) and the natural antioxidant studied showed an increase with age and a good relationship with lipids. These data suggest that retinol and tocopherols, well known scavengers of free radicals, are involved, at least partially, in the prevention of oxidative damage of circulating proteins.