Relationship Between the Regulation of Enkephalin‐Containing Peptide and Dopamine β‐Hydroxylase Levels in Cultured Adrenal Chromaffin Cells

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Abstract
Adrenal medullary chromaffin cells were maintained under conditions known to increase their cellular levels of enkephalin-containing peptides and the effects of these treatments on another chromaffin vesicle component, dopamine .beta.-hydroxylase, were examined. Catecholamine-depleting drugs, such as tetrabenazine, and cyclic nucleotide-elevating drugs, including forskolin, 8-bromo-cyclic AMP, and theophylline, increase chromaffin cell enkephalin-containing peptide levels but fail to increase dopamine .beta.-hydroxylase. In contrast, insulin treatment increases the levels of both enkephalin-containing peptides and dopamine .beta.-hydroxylase. The increased amounts of enkephalin-containing peptides produced by tetrabenazine and by insulin are stored in subcellular particles with properties identical to chromaffin vesicles on density-gradient centrifugation. These results suggest that following insulin treatment chromaffin cells synthesize new chromaffin vesicles with a full complement of enkephalin-containing peptides, but that after treatment with catecholamine-depleting or cyclic nucleotide-related agents enkephalin-containing peptides can be inserted into preexisting vesicles or that new vesicles, made as a part of the normal turnover of cellular components, contain elevated peptide levels.