Lipofuscin in bovine muscle and brain: a model for studying age pigment.

Pigment of brown atrophy of bovine muscle was interpreted as an exacerbation of age pigment accumulation that also occurred in brain. Isolated muscle pigment was able to be solubilised in LDS/beta-mercaptoethanol and found to be composed mainly of protein and lipid. The widespread "assumptive" hypothesis that age pigment reflects insoluble products of lipid/protein peroxidation is questioned. The methodology described allows for further in-depth analyses to test this and other hypotheses based on alternate models of protease resistant protein/lipid complexes of limited solubility.