Brain ischemia was produced in gerbils (Meriones unguiculatus) by the bilateral
ligation of the carotid arteries with reported procedures. Changes in the energy status of brain demonstrated that carotid
ligation was effective. At different time intervals from
ligation, groups of gerbils were given either saline of
S-Adenosyl-L-methionine (SAMe) by the intraventricular (i.v.) route (1.6 mg/Kg body wt. twice, at each 10 min interval), or by the intraperitoneal (i.p.) administration (200 mg/Kg body wt.) or subcutaneously (s.c.) with 40 mg/Kg body wt, daily, for two weeks. Control animals, with and without SAMe, together with the ischemic groups, were decapitated directly into liquid
nitrogen, 10 min after
ligation. Brain neutral and polar
lipid, together with
free fatty acids, which were all labeled in vivo by the
intraventricular injection of [1-14C]
arachidonic acid 2 hr prior to
ligation, were extracted, purified and separated by conventional procedures. SAMe when injected i.v. or i.p. noticeably corrected the changes in polar
lipid by reversing the decrease of brain
phosphatidylcholine and
choline plasmalogen, as well as of their labeling, which was due to
ischemia. Concurrently with this action, SAMe treatment (i.v. and i.p.) also provided to some extent to re-establish the normal level of labeling of
ethanolamine lipids. When SAMe was given s.c., no effect was present. SAMe had no effect on the increase of
free fatty acid and diglyceride due to
ischemia. The prevention by SAMe of the changes of
choline lipids suggests that a stimulation of the
methyltransferase reaction may occur in the ischemic brain, due to increased substrate (SAMe) availability. This effect may be important for cell survival, since membrane
phospholipid derangements alter the properties of the membrane.