Electrophoretic analysis of brain proteins from young adult and aged mice

The purpose of this study was to electrophoretically examine proteins from mice of different ages to determine whether general changes occurred in protein levels during senescence and to relate the data to specific ageing hypotheses involving proteins. Proteins from whole brain, brain regions, soluble and ribosomal brain fractions, from young adult and senescent mice, were totally solubilized and subjected to polyacrylamide slab gel electrophoresis. The resulting gel patterns were than compared by examining the intensity of gel bands of the same migration distance. Positive controls were used to establish the high sensitivity of the electrophoretic method. For example, band intensity differences were observed when brain proteins from different species, different periods of growth and development, normal and mutant mice, and different brain regions were compared. Virtually all band intensities and therefore, corresponding brain protein concentrations were unchanged when patterns from senescent mice were compared to patterns from younger adult mice. These results provide evidence against ageing hypotheses involving: (1) progressive programmed ageing; (2) protein cross-linking, and (3) a systematic shutdown of gene activity. The few, select, protein band changes that did occur provide evidence that (1) the volume of the brain vascular system decreases with age, and (2) the brain S-100 protein concentration increases with age.