Extracellular changes of inorganic phosphate are different during spreading depression and global cerebral ischemia of rats.
Tissue levels of inorganic phosphate (iP-) and lactate (lac) increase during cerebral ischemia and cortical spreading depression (SD). Since cell membranes become leaky during these insults, iP- and lac were expected to leak into the extracellular space (ECS). In order to find out whether this occurs or does not, a microdialysis (MD) fiber was implanted into the cortex of anesthetized rats and extracellular lactate (lac(e)) and extracellular iP- (iPe-) were determined during various insults. Extracellular lactate increased to about the same extent during ischemia and SD. In contrast, iPe- increased during ischemia but not during SD. Instead, iPe- started to rise after SD and reached its maximum about 45 min later. The distinct pattern of iPe- in comparison to lac(e) during the above mentioned insults points to a qualitative difference of the underlying mechanisms: whereas lac appears within the ECS at any stressful situation, elevation of iP- within the ECS indicates depletion of energy stores in parallel to the lack of control of ion homeostasis.
Scheller
D
D
Janssen Research Foundation, Neuss, FRG.
Kolb
J
J
Tegtmeier
F
F
Lehmenkühler
A
A
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002545:Brain Ischemia / Q000378:metabolism*; D013181:Cortical Spreading Depression / Q000502:physiology*; D003956:Dialysis / Q000379:methods; D005110:Extracellular Space / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D051381:Rats
D010710:Phosphates