IONIC AND METABOLIC REQUIREMENTS FOR STIMULATION OF SECRETION BY OUABAIN IN BOVINE ADRENAL-MEDULLARY CELLS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 23  (3) , 671-680
Abstract
The effect of ouabain on the secretion of catecholamines from isolated bovine adrenal medullary cells was investigated. Ouabain enhances the basal rate of secretion approximately 2-fold, with half-maximal stimulation occurring at a glycoside concentration of .apprx. 5 .times. 10-7 M. Parallel measurements of the release of dopamine .beta.-hydroxylase (EC 1.14.17.1) (an enzyme associated with chromaffin granules) and lactate dehydrogenase (EC 1.1.1.27) (which is confined to the cytosolic compartment) suggest that this increase in secretion occurs as a result of an enhanced rate of exocytosis rather than by any other route. The stimulatory effect of ouabain is dependent on extracellular Na but is maintained in the nominal absence of Ca and is unaffected by changes in the major external anion. Neither tetrodotoxin nor phenoxybenzamine alters the response to glycoside treatment, but the Ca channel blocker methoxyverapamil reduces the catecholamine secretion evoked by ouabain in a dose-dependent fashion. The secretory action of ouabain in isolated chromaffin is characterized, and a foundation for other ion flux studies is provided.