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Regulation of Melatonin Release and N‐Acetyltransferase Activity in Ovine Pineal Cells
Author(s) -
Camp Gilles,
Ravault JeanPaul,
Falcón Jacky,
Collin JeanPierre,
Voisin Pierre
Publication year - 1991
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1991.tb00306.x
Subject(s) - melatonin , pinealocyte , medicine , endocrinology , forskolin , stimulation , chemistry , biology , pineal gland
A suspension culture of ovine pineal cells was developed to investigate the regulation of melatonin synthesis and release. Dosedependent stimulation of melatonin release by a series of adrenergic agonists yielded a typical β‐adrenergic profile. Serotonin N‐acetyltransferase (NAT), the rate‐limiting enzyme in melatonin biosynthesis, was also stimulated by a β‐adrenergic mechanism. However, NAT activity appeared less sensitive than melatonin release to β‐adrenergic stimulation. No evidence was obtained for a contribution of α 1 ‐adrenergic receptors to the regulation of NAT activity and melatonin release. Activation of adenylate cyclase by forskolin or addition of a cyclic AMP analogue increased both melatonin release and NAT activity. In contrast, the Ca 2+ ionophore A 23187 stimulated melatonin release without a detectable increase in NAT activity. Together, the present data argue for a β‐adrenergic regulation of both NAT activity and melatonin release in ovine pinealocytes. The evidence also suggests that two intracellular mechanisms may control melatonin release in ovine pinealocytes: a cyclic AMP‐dependent mechanism, associated with an increase in NAT activity and a Ca 2+ ‐dependent mechanism, independent of NAT activity.