Current concepts: I. The relationship between age-related changes in gene expression, protein turnover, and the responsiveness of an organism to stimuli.

A general decline in gene expression, translation and transcription, has been observed to occur with increasing age in a wide variety of organisms and tissues. Because the level of most enzymes and proteins remains relatively constant with increasing age, one would predict that the decline in gene expression would result in an age-related decline in protein turnover. Recent studies show that protein turnover in mouse liver and nematodes declines with increasing age. The decline in protein turnover could lead to an age-related decrease in the response of inducible enzymes to stimuli. This could explain the molecular basis for the decline in aging organisms to respond to a variety of environmental factors.