The mode of
free fatty acid (FFA) liberation from the mouse brain during
ischemia was investigated at various times after
decapitation and under
nizofenone treatment. Normal nonischemic brain FFAs consist mainly of
palmitic acid (16:0),
stearic acid (18:0), and
oleic acid (18:1) with smaller amounts of
arachidonic acid (20:4),
docosahexaenoic acid (22:6), and others. Postdecapitative
ischemia induced a rapid, biphasic release of 20:4 after a short lag of less than 30 s. The first phase showed a rapid 6.4-fold increase within 1 min of
decapitation, followed by the second phase involving a slow release at less than one-fifth the rate of the first phase and lasting for at least 10 min. A similar, but not so marked, biphasic liberation was observed with 18:0. However, all of the other
fatty acids (16:0, 18:1, 22:6, and others) were released only in a single phase at a slow rate. The time course for the rapid and specific liberation of 20:4 coincided with the time course for the decrease in brain
ATP concentration during
ischemia. Pretreatment of the animals with
nizofenone resulted in a marked suppression of both FFA liberation and
ATP depletion during
ischemia. This suppression was particularly noteworthy with 20:4 and 18:0. The present study indicates that there is a specific and rapid liberation of 20:4 and 18:0 in a very early stage of
ischemia and that this liberation seems to depend on availability of
ATP in the brain. The physiological role of this transient 20:4 liberation during
ischemia is discussed.