Prolonged ischemia differently affects phospholipase C acting against phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate in brain subsynaptosomal fraction.
The effect of 10 min ischemia on the activity of phospholipase C acting against [3H]inositol-phosphatidylinositol (PI) and [3H]inositol-phosphatidylinositol 4,5-bisphosphate (PIP2) in the brain subsynaptosomal fractions was investigated. In the presence of endogenous CaCl2, specific activity of phospholipase C acting on phosphatidylinositol was as follows: synaptic cytosol (SC) greater than synaptic vesicles (SV) greater than synaptic plasma membrane SPM). Brain ischemia activated phospholipase C acting on PI by about 60% and 40% in SV and SPM, respectively. The enzyme of synaptic cytosol was not affected by ischemic insult. Phospholipase C acting against PIP2 in the presence of endogenous calcium expressed the specific activity in the following order: SV greater than SPM greater than SC. After 10 min of brain ischemia, activity of phospholipase C acting on PIP2 was significantly suppressed in all subsynaptosomal fractions by about 50-60%. These results indicate that prolonged ischemia produced activation exclusively of phospholipase C acting against phosphatidylinositol.
Strosznajder
J
J
Department of Neurochemistry, Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002545:Brain Ischemia / Q000201:enzymology*; D003600:Cytosol / Q000201:enzymology; D005849:Gerbillinae; D007700:Kinetics; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism*; D013379:Substrate Specificity; D013569:Synapses / Q000201:enzymology*; D013570:Synaptic Membranes / Q000201:enzymology; D013572:Synaptic Vesicles / Q000201:enzymology; D013574:Synaptosomes / Q000201:enzymology*; D010738:Type C Phospholipases / Q000378:metabolism*
D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D010738:Type C Phospholipases