Biochemical and functional evidence for the cosecretion of multiple messengers from single and multiple compartments

Examination of the secretory profile and subcellular localization of some of the multiple export products of the adrenal medullary chromaffin cells indicates that several compartments (chromaffin vesicle, lysosomes, endoplasmic reticulum) are coupled to specific receptors and to cell depolarization through Ca2+-dependent mechanism(s). The activation of the release process results in the concerted cosecretion of endogenous catecholamines, newly incorporated catecholamines, adenine nucleotides, chromogranins, dopamine beta-hydroxylase (EC 1.14.17.1), enkephalins and related opioid peptides, stored ascorbate and newly incorporated ascorbate, lysosomal hydrolases, and soluble acetylcholinesterase. This complex organization for the coexistence of these multiple putative messengers and their cosecretion may be relevant to other endocrine cells and neurons where coexistence of transmitters has been found. This coexistence in multiple secretory compartments may provide the subcellular basis for independent regulation of the synthesis, packaging, and secretion of individual transmitters within the multiplicity of putative messengers secreted by a particular endocrine cell or nerve terminal.