Abstract
The regulatory role of intracellular sodium ion in the release of catecholamine and calcium movement was studied by using perfused bovine adrenal medulla. Ouabain (2x10-7 M), a well known inhibitor of the sodium pump, did not cause release of catecholamine, but potentiated and prolonged catecholamine release evoked by carbamylcholine. The influx of 45Ca was stimulated, whereas the efflux of 45Ca was inhibited when catecholamine release was potentiated and prolonged in the presence of ouabain. Under these conditions, the sodium content of the medullary cells was found to be elevated. These results suggest that elevation of intracellular sodium ion may be accompanid by an increase of free calcium in the cell, resulting in an increase in the catecholamine release.
