title: Activities of calcineurin and phosphatase 2A in the hippocampus after transient forebrain ischemia.
abstract: We investigated the changes in the enzyme activity and immunoreactivity of calcineurin in the rat hippocampus after transient forebrain ischemia. Immediately after 20-min transient forebrain ischemia, calcineurin activity decreased to about 40% of the control in the CA1 region and to about 55% in other regions. Protein phosphatase 2A activity showed no remarkable changes. By 12 h after ischemia, calcineurin activity recovered, more in the CA1 region than in other regions. At 24 h it decreased again, but only in the CA1 region. Immunohistochemical- and immunoblot analyses showed no remarkable change in calcineurin in any region of the hippocampus within 12 h after ischemia. Thus, the activity of calcineurin is dissociated from its immunoreactivity and quantity. Several studies have suggested that unknown inhibitory factor(s) and/or reversible changes in calcineurin act to modify enzyme activity after ischemia. In contrast, phosphatase 2A activity underwent no obvious changes during the post-ischemia period we examined. This unique time course of calcineurin activity may contribute to the mechanism of ischemic neuronal injury.
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000032:analysis / Q000378:metabolism*; D018891:Dentate Gyrus / Q000098:blood supply / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D005296:Ferrous Compounds / Q000494:pharmacology; D015151:Immunoblotting; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000494:pharmacology; D002546:Ischemic Attack, Transient / Q000188:drug therapy / Q000378:metabolism*; D008297:Male; D010749:Phosphoprotein Phosphatases / Q000032:analysis / Q000378:metabolism*; D016548:Prosencephalon / Q000098:blood supply / Q000201:enzymology; D054648:Protein Phosphatase 2; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions / Q000201:enzymology; D016559:Tacrolimus / Q000494:pharmacology