Facilitation of acetylcholine-evoked catecholamine release by cyclic AMP on isolated perfused dog adrenal glands

The effects of cyclic nucleotides on catecholamine (CA) release and Ca2+ efflux were determined on isolated dog adrenals perfused with 1.3 mM Ca2+ containing fluid except indicated. Dibutyryl cyclic AMP (DBcAMP, 50 microM--1 mM) substantially enhanced CA release evoked by acetylcholine (ACh) and slightly increased the spontaneous CA release. Dibutyryl cyclic GMP (100-500 microM) narrowly increased the basal CA release. DBcAMP, 200 microM also significantly facilitated CA release caused by nicotine, bethanechol and excess K+, and by caffeine in the absence of extracellular Ca2+. 45Ca efflux evoked by ACh and by caffeine in the absence of extracellular Ca2+ from prelabelled adrenals with 45Ca was enhanced significantly by DBcAMP, 200 microM. These results suggest that cAMP may function as a facilitatory modulator in CA release from the adrenal medulla via in part the effect on Ca2+ flux including alterations in the function of systems for intracellular Ca2+ homeostasis.