SEIZURE-INDUCED ALTERATIONS OF PLASMA-MEMBRANE CALCIUM-ATPASE ISOFORM-1, ISOFORM-2 AND ISOFORM-3 MESSENGER-RNA AND PROTEIN IN RAT HIPPOCAMPUS

Improper intracellular regulation of the ubiquitous second messenger, calcium, has been linked to several pathological conditions. The plasm a membrane calcium ATPase (PMCA) is one of the primary systems for tra nslocating calcium from the cytosol to the extracellular milieu. As an initial assessment of the possible involvement of PMCAs in kainate (K A)-induced neurodegeneration, pie have determined the effect of KA-ind uced seizures upon PMCA mRNA and protein. In situ hybridization was pe rformed on tissue from adult male Sprague-Dawley rats sacrificed at va rious time points following i.p. injection of KA. KA altered the expre ssion within the hippocampal subfields for mRNAs of PMCA isoforms 1 an d 2. PMCA 1 and 2 mRNAs exhibited hybridization below control levels 1 2-48 h post-injection within CA1 and CA3. Within the dentate gyrus, PM CA 2 mRNA hybridized below control levels 4 h post-injection, but reco vered to control levels by 24 h post-injection. Alterations in combine d PMCA protein levels occurred at all time points examined post-inject ion. These observations provide evidence that KA-induced seizures alte r the PMCAs at the mRNA and protein levels, suggesting a possible role for this calcium efflux system in the neuronal degeneration inherent to this paradigm.