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Role of extracellular calcium on the regulation of melatonin synthesis in the Syrian hamster pineal gland
Author(s) -
Santana Celsa,
Moujir Fatima,
Sanchez JuanJose,
Reiter Russel J.,
Abreu Pedro
Publication year - 2001
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1034/j.1600-079x.2001.310401.x
Subject(s) - forskolin , melatonin , hamster , medicine , endocrinology , calcium , extracellular , pineal gland , biology , period (music) , darkness , stimulation , biochemistry , botany , physics , acoustics
The role of extracellular calcium on the induction of cyclic AMP production, N‐acetyltransferase (NAT) activity and melatonin synthesis, induced by forskolin, was investigated in Syrian hamster pineal glands. Pineals were removed from hamsters killed either in the first half of the normal dark period or late in the dark period. Forskolin immediately increased NAT activity and melatonin levels only when the glands were collected late in the dark period, while in the first half of the dark phase, hamster pineals responded to forskolin with an increase of NAT activity and melatonin production only after 6 hr of incubation. The absence of calcium prevented the induction of melatonin synthesis by forskolin only when glands were collected early in the dark phase and incubated for 6 hr. In the second half of the normal dark period removal of calcium markedly decreased NAT activity and melatonin levels in glands incubated with forskolin for either 4 or 6 hr. However, the absence of extracellular calcium had no significant effect on the induction of cyclic AMP production by forskolin in pineals collected either early in the dark period or late in the dark phase. These data indicate that at least part of the action of extracellular calcium is indirect and that it affects steps in the induction of melatonin synthesis beyond the accumulation of cAMP.