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Melatonin suppresses the induction of AP-1 transcription factor components in the pars tuberalis of the pituitary

1996; Elsevier BV; Volume: 123; Issue: 1 Linguagem: Inglês

10.1016/0303-7207(96)03897-x

1872-8057

Alexander Ross, Perry Barrett, Julian G. Mercer, Peter J. Morgan,

Growth Hormone and Insulin-like Growth Factors

In ovine pars tuberalis cells which express high affinity Mel 1a melatonin receptors, the ability of melatonin to directly stimulate or inhibit AP-1 transcription factor gene expression was studied. Effects of melatonin upon mRNA expression by forskolin, serum and IGF-1 were also investigated. Northern analysis showed melatonin had no direct stimulatory nor inhibitory effect upon transcription or translation. Melatonin was able to significantly inhibit forskolin-stimulated induction of c-fos and jun B mRNA whilst forskolin had no effect upon c-jun or jun D. Induction of c-Fos translation by forskolin was also inhibited by melatonin. Serum induced c-fos and c-jun, but melatonin was unable to affect these changes. Similarly IGF-1 stimulated c-fos and melatonin had no effect upon this induction. From these results it can be concluded that melatonin has no independent effects on expression of the AP-1 genes, rather its primary function is to inhibit cell activities through cyclic AMP-dependent routes of gene activation.