p-Chloromercuribenzoate Causes Ca2+-Dependent Exocytotic Catecholamine Secretion from Cultured Bovine Adrenal Medullary Cells

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Abstract
Incubation of cultured bovine adrenal medullary cells with p-chloromercuribenzoate (50–500 μM), a sulfhy-dryl-reacting agent, caused an increase in the secretion of catecholamines. p-Chloromercuriphenyl sulfonate, a p-chlo-romercuribenzoate analogue that poorly penetrates the cell membrane, caused a similar increase in catecholamine secretion. In both cases, catecholamine secretion was dependent on extracellular Ca2+. Furthermore, p-chloromercuribenzoate caused both 45Ca2+ influx into the cells and an increase in the intracellular free Ca2+ concentration. The increases in catecholamine secretion and 45Ca2+ influx behaved similarly in relation to p-chloromercuribenzoate concentration. The time courses of the increased secretion, 45Ca2+ influx, and intracellular free Ca2+ concentration by p-chloromercuri-benzoate were also quite similar. The stimulation of cate-holamine secretion by p-chloromercuribenzoate was reversed by washing the cells with dithiothreitol-containing medium, but not by dithiothreitol-free medium. When the cells were treated with p-chloromercuribenzoate, dopamineβ-hydroxylase, an enzyme present in the chromaffin granules along with catecholamines, was also released. However, p-chloromercuribenzoate did not cause release of phenyletha-nolamine-JV-methyltransferase, an enzyme present in the cytoplasm. These results indicate that catecholamine secretion due to p-chloromercuribenzoate occurs by Ca2+-dependent exocytosis.

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