Catecholamine secretion from bovine adrenal chromaffin cells: the role of the Na+/Ca2+ exchanger and the intracellular Ca2+ pool.
The role of the Na+/Ca2+ exchanger and intracellular nonmitochondrial Ca2+ pool in the regulation of cytosolic free calcium concentration ([Ca2+]i) during catecholamine secretion was investigated. Catecholamine secretion and [Ca2+]i were simultaneously monitored in a single chromaffin cell. After high-K+ stimulation, control cells and cells in which the Na+/Ca2+ exchange activity was inhibited showed similar rates of [Ca2+]i elevation. However, the recovery of [Ca2+]i to resting levels was slower in the inhibited cells. Inhibition of the exchanger increased the total catecholamine secretion by prolonging the secretion. Inhibition of the Ca2+ pump of the intracellular Ca2+ pool with thapsigargin caused a significant delay in the recovery of [Ca2+]i and greatly enhanced the secretory events. These data suggest that both the Na+/Ca2+ exchanger and the thapsigargin-sensitive Ca2+ pool are important in the regulation of [Ca2+]i and, by modulating the time course of secretion, are important in determining the extent of secretion.
Pan
C Y
CY
Institute of Biomedical Sciences, Academia Sinica, and Department of Biochemistry, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Kao
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LS
D000313:Adrenal Medulla / Q000166:cytology / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002352:Carrier Proteins / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D004563:Electrochemistry; D005089:Exocytosis / Q000187:drug effects; D006706:Homeostasis; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D019831:Sodium-Calcium Exchanger; D019284:Thapsigargin / Q000494:pharmacology
D002352:Carrier Proteins; D002395:Catecholamines; D019831:Sodium-Calcium Exchanger; D019284:Thapsigargin; D012964:Sodium; D000252:Calcium-Transporting ATPases; D011188:Potassium; D002118:Calcium