| MadSci Network: Biochemistry |
Dear James,
There are actually different electrical gradients established by cells across plasma membranes (PM’s) for a variety of functions. For example, the cellular membrane defining the barrier between inside and outside of the cell, or the inner mitochondrial membrane across which protons are pumped to drive ATP synthesis. What happens as cells age, and the zeta potential decreases, is a very complicated problem which is the subject of a great research interest at the moment.
It is believed that damage to enzymes (e.g., through oxidative damage) responsible for maintaining these electrical gradients through the pumping of ions such as (sodium potassium-ATPases) Na+,K+- ATPases is one culprit (1).
Other enzymes are responsible for controlling the lipid composition of PM's which helps to establish the electrical gradient across the PM. Furthermore, the Na+,K+-ATPases are sensitive to changes in the lipid composition of the PM, which can affect their ability to maintain the integrity of the PM, resulting in a reduced potential (2).
Because the age-related drop in zeta potential is related to oxidative protein damage, the bad news is the simply adding electrolytes don’t seem to be likely to do much (if any) good. The good news however, is that recent studies in rats have shown that dibunol (BHT), an anti-oxidant seemed to restore much of the PM’s function (3).
The maintenance of the mitochondrial membrane is also crucial because the mitochondrion is where ATP (which is the energy currency of the body), syntheses occurs. Oxidative damage in the mitochondrion has also been implicated in aging. Studies in rats have shown that feeding old animals the mitochondrial metabolites acetylcarnitine, and lipoic acid (also and antioxidant), can restore mitochondrial function (4).
1. Chakraborty H, Sen P, Sur A, Chatterjee U, Chakrabarti S. Age-related oxidative inactivation of Na+, K+-ATPase in rat brain crude synaptosomes. Exp. Gerontol. 2003, 38(6): 705-710.
2. Tanaka Y and Ando S Synaptic aging as revealed by changes in membrane potential and decreased activity of Na+,K(+)-ATPase. Brain Res, 1990, 506(1):46-52
3. Frolkis VV, Tanin SA, Gorban EN, Bogatskaya LN, Sabko VE Membrane potential of cells and its regulation during aging. 1. Report: the role of energetic metabolism and plasma membrane phospholipid contents. ZFA. 1987 42(2):67- 75
4. Ames BN, Liu J, Delaying the mitochondrial decay of aging with acetylcarnitine. Ann. N. Y. Acad. Sci. 2004 1033:108-116
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