Characterization of a Na+-Ca2+ exchanger NCX1 isoform in bovine fasciculata cells of adrenal gland

The Na+-Ca2+ exchanger (NCX) is well known to regulate intracellular Ca2+ c oncentration in many excitable cells. To date, three members of the NCX exc hanger gene family have been identified: NCX1, NCX2 and NCX3. In zona fasci culata of the bovine adrenal gland, a Na+-Ca2+ exchanger has been recently found to display biochemical similarities with the NCX1 exchanger of renal basolateral cells. Although a Na+-Ca2+ exchanger has already been character ized in zona medulla of adrenal gland, such an exchanger has never been stu died in the adrenal cortex. Thus, we have used a reverse transcriptase-poly merase chain reaction (RT-PCR) assay with specific NCX primers on fascicula ta cell cultures. The sequencing of the amplified fragment revealed, for th e first time, the presence of a NACA3 isoform of the NCX1 exchanger in the adrenal cortex, similar to the one found in adrenal chromaffin cells and in renal cortex. This isoform is 92 and 94% identical in the portion compared with kidney Na+-Ca2+ exchanger NACA3 of rat and pig, respectively.