Enkephalin biosynthesis in adrenal medulla. Modulation of proenkephalin mRNA content of cultured chromaffin cells by 8-bromo-adenosine 3',5'- monophosphate

TT Quach, F Tang, H Kageyama, I Mocchetti, A Guidotti, JL Meek, E Costa and JP Schwartz

Incubation of primary cultures of chromaffin cells from bovine adrenal medulla with 8-bromo-adenosine 3',5'-monophosphate (8-Br-cyclic AMP) resulted in an increase in proenkephalin mRNA content. The mRNA that increased was detected by hybridization analysis using a cDNA probe and migrated with an apparent size of approximately 1400 bases. The increase in proenkephalin mRNA following 8-Br-cyclic AMP treatment was apparent in 12 hr and continued over 2 days. Corresponding changes were detected in enkephalin-like immunoreactivity but with a 24-hr lag: the cellular content increased significantly after 2 days of treatment and continued to rise over the next 2 days, whereas changes in the amount released to the medium followed the same time course. Dose-response curves for the increase in the content of proenkephalin mRNA and of enkephalin-containing peptides were essentially identical. Chromatographic characterization of the enkephalin-like peptides demonstrated that 8-Br-cyclic AMP increased both the high molecular weight fraction and the low molecular weight fraction, which was shown by high-pressure liquid chromatography to contain Met5-enkephalin, Leu5- enkephalin, and Met5-enkephalin-Arg6-Phe7. Previous results in chromaffin cells have demonstrated that the synthesis of tyrosine hydroxylase is also regulated by cyclic AMP, with a similar time course. These results therefore suggest the possibility of coordinate regulation by cyclic AMP of the expression of the cotransmitters, catecholamines and enkephalin peptides, in the adrenal medulla.

Volume 26, Issue 2, pp. 255-260, 09/01/1984
Copyright © 1984 by American Society for Pharmacology and Experimental Therapeutics