Seizure-induced alterations of plasma membrane calcium ATPase isoforms 1, 2 and 3 mRNA and protein in rat hippocampus

Improper intracellular regulation of the ubiquitous second messenger, calcium, has been linked to several pathological conditions. The plasma membrane calcium ATPase (PMCA) is one of the primary systems for translocating calcium from the cytosol to the extracellular milieu. As an initial assessment of the possible involvement of PMCAs in kainate (KA)-induced neurodegeneration, we have determined the effect of KA-induced seizures upon PMCA mRNA and protein. In situ hybridization was performed on tissue from adult male Sprague-Dawley rats sacrificed at various time points following i.p. injection of KA. KA altered the expression within the hippocampal subfields for mRNAs of PMCA isoforms 1 and 2. PMCA 1 and 2 mRNAs exhibited hybridization below control levels 12-48 h post-injection within CA1 and CA3. Within the dentate gyms, PMCA 2 mRNA hybridized below control levels 4 h post-injection, but recovered to control levels by 24 h post-injection. Alterations in combined PMCA protein levels occurred at all time points examined post-injection. These observations provide evidence that KA-induced seizures alter 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.