[Catecholaminergic secretions and monovalent cations in adrenal medulla]

Taken together the results of this work indicate that 1st) The countertransport systems, [Na+]i-[Ca2+]o or [Li+]i-[Ca2+]o are implicated on the catecholamine secretory response evoked by ouabaine and lithium in the cat adrenal medulla. 2nd) Both procedures (ouabain, or lithium) induce an increment of cytosolic [Ca2+]i, secundary to the accumulation of monavalents cations (Na+ or Li+) in the cytosol, which is finally responsible for the catecholamine secretory response and 3rd) In addition to [Na+]i-[Ca2+]o or [Li+]i-[Ca2+]o counter transport systems, either Na+ or Li+ could depolarize the cell and therefore activate voltage-dependent Ca2+, and possibly Na+ channels leading to further increments of [Ca2+]i.