The co-presence of Na+/Ca2+-K+ exchanger and Na+/Ca2+ exchanger in bovine adrenal chromaffin cells.
We have previously shown that there is high Na(+)/Ca(2+) exchange (NCX) activity in bovine adrenal chromaffin cells. In this study, by monitoring the [Ca(2+)](i) change in single cells and in a population of chromaffin cells, when the reverse mode of exchanger activity has been initiated, we have shown that the NCX activity is enhanced by K(+). The K(+)-enhanced activity accounted for a significant proportion of the Na(+)-dependent Ca(2+) uptake activity in the chromaffin cells. The results support the hypothesis that both NCX and Na(+)/Ca(2+)-K(+) exchanger (NCKX) are co-present in chromaffin cells. The expression of NCKX in chromaffin cells was further confirmed using PCR and northern blotting. In addition to the plasma membrane, the exchanger activity, measured by Na(+)-dependent (45)Ca(2+) uptake, was also present in membrane isolated from the chromaffin granules enriched fraction and the mitochondria enriched fraction. The results support that both NCX and NCKX are present in bovine chromaffin cells and that the regulation of [Ca(2+)](i) is probably more efficient with the participation of NCKX.
Pan
Chien-Yuan
CY
Institute of Zoology and Department of Life Science, National Taiwan University, Taipei, Taiwan.
Tsai
Ling-Ling
LL
Jiang
Jhih-Hang
JH
Chen
Lih-Woan
LW
Kao
Lung-Sen
LS
D000818:Animals; D015152:Blotting, Northern; D002417:Cattle; D019439:Chromaffin Cells / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*
D019831:Sodium-Calcium Exchanger; C074530:potassium-dependent sodium-calcium exchanger