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Effects of thyroid hormone on light/dark melatonin synthesis and release by young and maturing rat pineal glands in vitro
Author(s) -
Catala M. D.,
Quay W. B.,
Timiras P. S.
Publication year - 1988
Publication title -
international journal of developmental neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.761
H-Index - 88
eISSN - 1873-474X
pISSN - 0736-5748
DOI - 10.1016/0736-5748(88)90008-1
Subject(s) - melatonin , medicine , endocrinology , pineal gland , triiodothyronine , hormone , in vitro , thyroid , biology , radioimmunoassay , circadian rhythm , chemistry , biochemistry
Synthesis and release of melatonin were studied in pineal expiants from 14‐ (young) and 60‐day‐old (‘maturing’) male Long‐Evans rats with or without added thyroid hormone, triiodothyronine (T 3 ), at or near physiological levels and under light and dark conditions. Incubation for 6 hr (1200–1800) was in a synthetic medium; melatonin was measured by radioimmunoassay (RIA). In light, T 3 increased melatonin levels in pineal and medium of cultures from either young or maturing animals. In dark, T 3 decreased melatonin levels in the pineals of either age, but was without significant effect on levels in the medium. Since it is known from other work that 14‐day‐old rat pineal glands do not yet have a complete sympathetic innervation system, it is here doubly evident that T 3 can modulate directly pineal synthesis and release of melatonin, and may not depend upon a mature sympathetic innervation. Light in the studied conditions was permissive from the stimulatory action of T 3 on pineal synthesis and release of melatonin in vitro .