Delta-6 desaturation of alpha-linolenic acid in brain and liver during development and aging in the mouse.

During pre- and postnatal brain development, delta-6 desaturase decreased dramatically (approx. 4-fold) up to weaning, slowly (2-fold) up to 3 months, and remained nearly constant and extremely low thereafter. In contrast, in liver, the activity increased approximately 7-fold between day 3 before birth and day 11 after birth, then decreased slightly up to weaning, and was constant up to 9 months. Subsequently, the activity decreased during aging (4-fold between 9 and 26 months). During aging, the reduced activity in liver and the very low activity in brain raise the question of the origin of polyunsaturated fatty acids participating in the physiological turnover of brain membranes.