Changes in the calcium transport systems of rat brain synaptosomes and their possible role in the pathophysiology of aging

Studies were undertaken on the age-associated peculiarities of the Ca2+ transport systems of the rat brain synaptosomes. It has been found that 45Ca2+ uptake reduced with ageing. The above reduction was not linked with the changes in the permeability of potential-dependent synaptosomal membrane Ca2+ depending upon the membrane potential. The distribution of calcium across the mitochondrial membrane changed with ageing, shifting towards higher extramitochondrial calcium levels in old rats, both in isolated and in synaptosomal mitochondria. While studying calcium efflux from mitochondria, it was found that, at equivalent calcium loads, the calcium efflux rates were slower in old rats as compared to adult animals. As observed, both resting [Ca2+]i and that obtained after K-depolarization drastically increased in old animals. The possible pathogenic mechanisms in neuronal injury, conditioned by this increase, are discussed.