IMMUNOLOCALIZATION OF THE PLASMA-MEMBRANE CA2-BRAIN( PUMP ISOFORMS INTHE RAT)

Ca2+ homeostasis in nerve cells is dependent on at least three mechani sms: Ca2+ channels, calcium-binding proteins and Ca2+ exchangers/pumps . Only limited information is available on the regional/cellular distr ibution of these Ca2+-regulating systems in the brain. The distributio n of three of the isoforms of one of the systems, plasma membrane Ca2-ATPase (PMCA), was analyzed in this study. Using antibodies against e pitopes specific for each isoform, a map of the distribution of the pu mp in the whole brain was produced. The pump was mainly expressed in n eurons and was apparently absent from glia cells. Isoform 1 was ubiqui tous and occurred in varying, but always significant, concentrations i n almost all nerve cells. Isoform 2 was abundant in cerebellar Purkinj e cells but less concentrated in other brain regions. Isoform 3 had a predominantly extra neuronal location, e.g. it was abundant in the cho roid plexuses. The three isoforms were found to be distributed in a hi ghly characteristic manner, suggesting that nerve cells have different requirements for the preservation of their intracellular calcium home ostasis.