On the relation between ATP splitting and secretion in the adrenal chromaffin cell: extrusion of ATP (unhydrolysed) during release of catecholamines

Abstract

Cats'' adrenal glands were acutely denervated and perfused in situ, with Locke''s solution. When the medullary secretogo-gue Ba (2-10 m[image]) was added to the perfusion medium, large amounts of AMP and traces of ATP were found in the venous effluent from the adrenal gland along with the catecholamines. In the respect Ba mimicked the physiological secretogogue, acetylcholine. Control perfusion with i known concentrations of ATP showed that under such conditions ATP was rapidly broken down within the adrenal vasculature. When such intravascular hydrolysis of ATP was suppressed by perfusion with a Ca-free, Mg-free Locke''s solution containing 1-2 m[image] EDTA, catechol-amine secretion induced by Ba was accompanied by the discharge of large amounts of ATP but relatively little AMP. The ATP that accompanied catecholamine secretion in such circumstances is assumed to derive from the "heavy" nucleotide-rich chromaffin granules and it is concluded that the mechanismf or catecholamine secretion does not depend onhydrolys is of the ATP within these granules. The release of ATP (unhydrolysed) supports the hypothesis that the chromaff in granules discharge their contents at the cell surface by the process of '' reverse pino-cytosis''.