A Genistein-Sensitive Na+/Ca2+ Exchange Is Responsible for the Resting [Ca2+]i and Most of the Ca2+ Plasma Membrane Fluxes in Stimulated Rat Cerebellar Type 1 Astrocytes

Na+ entry via glutamate transporter activates the reverse Na+/Ca2+ exchange and triggers ‐induced Ca2+ release in rat cerebellar Type‐1 astrocytes

“…While the presence of RyRs has been demonstrated in this preparation, their physiological significance was not clear (Langley and Pearce 1994;Simpson et al 1998;Golovina and Blaustein 2000;Matyash et al 2002;Beck et al 2004;Aley et al 2006). Our experimental (Goldman et al 1994;Takuma et al 1994;Blaustein and Lederer 1999 (Rojas et al 2004). In different preparations, there is evidence of an intimate association between the Na + /Ca 2+ exchanger and internal Ca 2+ stores (Juhaszova et al 1996).…”

“…Effect of short-and long-term pulses of free extracellular Na + solutions on the Ca 2þ i dependent Fluo-3 signal Previous results from our laboratory indicate that manipulations of the Na + electrochemical gradient (decrease in extracellular or increase in intracellular Na + ) cause profound changes in the resting [Ca 2+ ] i in cerebellar Type-1 astrocytes (Rojas et al 2004). In order to determine how the amount of Ca 2+ entering through the reverse Na + /Ca 2+ exchanger affects the levels of [Ca 2+ ] i , we exposed Type-1 astrocytes to 0Na,Ca solutions for short (< 20 s) or long (> 40 s) periods.…”

“…In a previous study (Rojas et al 2004), we demonstrated that cerebellar Type-1 astrocytes functionally express a highly dynamic Na + /Ca 2+ exchanger, which under normal physiological conditions (Ca 2+ extrusion mode), accounts for both the resting [Ca 2+ ] i and the Ca 2+ clearance that occurs during agonist activation. In addition, we have presented evidence indicating that in these cells, the balance of membrane calcium fluxes at rest involves a component of Ca 2+ entry through the Na + /Ca 2+ exchanger (Rojas et al 2004). Nevertheless, the role of this exchange mode in the astrocyte physiological function remains unknown.…”

“…Cellular viability was measured the same days as the GFAP test using a commercial market kit: calcein-AM and ethidium homodimer-1 (kit viability/cytotoxicity; Molecular Probes). More than 80% of the cells in our primary co-culture were viable; (iii) pharmacologically, more than 95% of the cells morphologicaly identified as Type-1 astrocytes, responded to nanomolar concentrations of ET-3 with a fast transient rise in [Ca 2+ ] i followed by a plateau higher than the resting fluorescence (Supattapone et al 1989;Rojas et al 2004). Other glial cells with the morphological appearance of Type-2 astrocytes or oligodendrocytes did not respond to this agonist (Rojas et al 2004);and (iv) Because of the fact that Fluo-3 is a non-ratiometric dye, we chose the ionomycin-heavy metal (Mn 2+ )-digitonin method used by Kao et al (1989) for calibrating the Fluo-3 signal in some cells (see Fig.…”

Astrocyte CD38: Links to Neuroinflammation in HAND

“…In addition, Ca 2+ waves are also used for long-distance communication between astrocytes via gap junction proteins, which in turn can be modulated by IL-1 (John et al, 1999). After a physiological task is completed, the cytosolic Ca 2+ levels return to normal by extrusion of Ca 2+ either via Na + /Ca 2+ exchangers or plasma membrane Ca 2+ -ATPases (Rojas et al, 2004;Rojas et al, 2007), while Ca 2+ mobilized from internal stores return to normal via sarco/ER Ca 2+ -ATPase (Bers, 2002;Wang et al, 2006;Liu et al, 2007). Some recent reports show that mitochondrial Ca 2+ uniporter may also act as a sink to trap off the excess [Ca 2+ ] i Parpura, 2008, 2009).…”