Adrenaline formation in noradrenaline-storing chromaffin cells in vitro induced by corticosterone

Organ cultures of extra-adrenal chromaffin cells obtained from 2-day-old rabbits were prepared in a medium composed of horse serum and Medium 199. Corticosterone, 10 μg./ml., was added to half the cultures; the remainder served as controls. After 6 days the explants were examined histochemically by light and electron microscopy or were homogenized and assayed for adrenaline and noradrenaline.

There was a marked increase in the concentration of adrenaline in the corticosterone-treated explants, accompanied by light and electron microscopic histochemical evidence for adrenaline storage. Mixtures of adrenaline- and noradrenaline-storing chromaffin granules were observed in the same chromaffin cell in corticosterone-treated specimens. The control cultures showed little change.

These findings are in keeping with the hypothesis that the local concentration of adrenocortical steroids is an important factor in determining whether chromaffin cells synthesize and store adrenaline or noradrenaline. At a concentration of corticosterone similar to that found in the adrenal venous sinuses of the normal rabbit substantial quantities of adrenaline appear in cells which normally almost entirely store noradrenaline.

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

1. Cats' adrenal glands were acutely denervated and perfused, in situ, with Locke's solution.2. When the medullary secretogogue Ba (2-10 mM) 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 this respect Ba mimicked the physiological secretogogue, acetylcholine.3. Control perfusions with known concentrations of ATP showed that under such conditions ATP was rapidly broken down within the adrenal vasculature.4. When such intravascular hydrolysis of ATP was suppressed by perfusing with a Ca-free, Mg-free Locke's solution containing 1-2 mM EDTA, catecholamine secretion induced by Ba was accompanied by the discharge of large amounts of ATP but relatively little AMP.5. 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 mechanism for catecholamine secretion does not depend on hydrolysis of the ATP within these granules.6. The release of ATP (unhydrolysed) supports the hypothesis that the chromaffin granules discharge their contents at the cell surface by the process of ;reverse pinocytosis'.