Calcium elevation elicited by reverse mode Na+/Ca2+ exchange activity is facilitated by intracellular calcium stores in bovine chromaffin cells.
The Na(+)/Ca(2+) exchanger (NCX) in plasma membranes either moves Ca(2+) out of (forward mode) or into (reverse mode) cells depending on the electrochemical gradient of these ions across the membrane. In this report, we characterize the sources responsible for the elevation in [Ca(2+)](i) elicited by reverse mode NCX activity. The elevation in [Ca(2+)](i) elicited by reverse mode NCX activity was significantly diminished by thapsigargin. KB-R7943 could only partially suppress the [Ca(2+)](i) change. Measurement of the [Ca(2+)](i) concurrent with reverse mode NCX current by perforated whole-cell patch showed that elevation in [Ca(2+)](i), but not the current, was inhibited by thapsigargin. The change in [Ca(2+)](i) response elicited by nicotinic acetylcholine receptor agonist was inhibited by thapsigargin. These suggest the importance of intracellular Ca(2+) stores in facilitating the [Ca(2+)](i) elevation elicited by reverse mode NCX activity under physiological condition.
Institute of Zoology, National Taiwan University, Taipei, Taiwan. cypan@ntu.edu.tw
Chien-Yuan
CY
Pan
Chau-Hua
CH
Huang
Chia-Hsueh
CH
Lee
D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D019831:Sodium-Calcium Exchanger / Q000378:metabolism / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology
D001896:Boron Compounds; D019831:Sodium-Calcium Exchanger; D012433:Ryanodine; D019284:Thapsigargin; C109986:2-aminoethoxydiphenyl borate; D002118:Calcium