Mechanism of Na+ deprivation-induced catecholamine secretion from freshly isolated bovine adrenal chromaffin cells.
We have studied the mechanism of Na+ deprivation-induced catecholamine secretion from freshly isolated bovine adrenal chromaffin cells. Na+ deprivation-induced catecholamine secretion depended on free extracellular Ca2+ concentrations and was almost parallel to 45Ca2+ influx into the cells under various experimental conditions. Furthermore, Na+ deprivation-induced 45Ca2+ influx and catecholamine secretion were actually induced by a relative Na+ concentration gradient across the plasma membrane, but not by simple omission of Na+ from the medium. These results indicate that the deprivation of Na+ from the medium changes the relative Na+ gradient across the plasma membrane and results in Ca2+ influx via a reverse mode of Na(+)-Ca(2+) exchange rather than by inducing Ca2+ entry through Ca2+ channels by eliminating the competition between extracellular Na+ and Ca2+.
Isosaki
M
M
Department of Pharmacology, Nara Medical University, Kashihara, Nara, Japan. misosaki@naramed-u.ac.jp
Nakashima
T
T
D000311:Adrenal Glands / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D002469:Cell Separation; D019439:Chromaffin Cells / Q000166:cytology* / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D005110:Extracellular Space / Q000378:metabolism; D012964:Sodium / Q000172:deficiency*
D002395:Catecholamines; D003470:Culture Media; D012964:Sodium; D002118:Calcium