Reserpine increases opiate-like peptide content and tyrosine hydroxylase activity in adrenal medullary chromaffin cells in culture

Abstract

Primary cultures of adrenal medullary chromaffin cells maintained in a serum-free medium retain high levels of both catecholamines and opiate-like peptides. Addition of reserpine (100nM) to the culture medium results in the exponential loss of cellular catecholamines ( t ½ = 1.5days) and in an elevation of opiate-like peptide content and tyrosine hydroxylase activity without altering total cell protein content. The maximum increase in opioid activity as a result of reserpine treatment averaged 230% of untreated cell levels and was reached by 2–3 days after initiation of treatment. A similar time-course was observed for the elevation of tyrosine hydroxylase activity. The increases of opiate-like peptides and tyrosine hydroxylase induced by reserpine are blocked by inclusion of actinomycin D or cycloheximide in the culture medium, suggesting that both messenger ribonucleic acid and protein synthesis are required for the induction. These data suggest that synaptic activation is not the only long-term regulator of opiate-like peptide and catecholamine biosynthesis in the adrenal medulla and that the biosynthesis of opiate-like peptides, which are components of chromaffin vesicles, and tyrosine hydroxylase, the cytoplasmic, rate-limiting enzyme in catecholamine biosynthesis, are coordinately regulated.