Age and organ difference in amount and distribution of autofluorescent granules in rats

The amount and distribution of autofluorescent granules in various organs and tissues of rats of different ages (2-, 11-, and 29.5-month-old) were compared by morphometrical analysis. The age-related increase of the granules was observed in the cardiac muscle and hepatic cells, but the amount of granules was little even in 29.5-month-old rats. In some other organs, the granules appeared early, at 2 months of age, increased up to 11 months, but thereafter no significant increase was observed. The autofluorescent granules are not merely considered to be an age-related pigment, but seems to be influenced by relationship to the cell metabolism and other functions.