Alteration of Growth Rate and Fibronectin by Imbalances in Superoxide Dismutase and Glutathione Peroxidase Activity
The free radical theory of aging, originally postulated by D. Harman (1956) assumes there is a single basic cause of aging which is modified by genetic and environmental factors (Harman, 1984). Oxidative free radicals, produced by normal metabolic processes, over time result in a progressive accumulation of damage that can not be fully repaired by cells. Recent work, however, suggests that cellular senescence is the result of programmed internal changes, and not accumulation of oxidative genetic damage. Results obtained by fusing different types of immortalized cells suggest that immortalization results from mutations in a small number of genes which other wise act to restrict the cell’s proliferative potential. When different types of immortalized cells were fused, some hybrids became mortal again, senesced, and died (Pereira-Smith, 1988). Thus, the phenotype of cellular senescence is dominant and immortal cells arise due to recessive changes in growth control mechanisms. During the normal aging process then, cellular control of gene expression is gradually lost. One of the mRNAs of these “senescence” genes was recently cloned and coded for fibronection, a membrane associated protein (Pereira-Smith, 1988).
KeywordsGSHPX Activity Glutathione Peroxidase Activity Cumene Hydroperoxide MnSOD Activity Free Radical Theory
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