Plasmalogen content in brains of newborn rats is about 2 μmoles/g of wet tissue and represents about 10% of total phospholipid. During growth, and after major increase in brain weight, phospholipid composition shifts to one containing about 20 to 25% plasmalogen (12 μmoles/g). Maximal rate of accumulation of plasmalogen in brain occurs in 20- to 24-day-old rats.