Premium
Analysis of the daily changes of melatonin receptors in the rat liver
Author(s) -
Venegas Carmen,
García José A.,
Doerrier Carolina,
Volt Huayqui,
Escames Germaine,
López Luis C.,
Reiter Russel J.,
AcuñaCastroviejo Darío
Publication year - 2013
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 - 10.1111/jpi.12019
Subject(s) - melatonin , pinealectomy , receptor , medicine , melatonin receptor , endocrinology , circadian rhythm , biology , intracellular , luzindole , pineal gland , microbiology and biotechnology
Melatonin membrane ( MT 1 and MT 2) and nuclear ( ROR α) receptors have been identified in several mammalian tissues, including the liver. The mechanisms regulating hepatic melatonin receptors are yet unknown. This study investigated whether these receptors exhibit daily changes and the effects of melatonin on their levels. Our results show that m RNA s for MT 1/ MT 2 receptors exhibit circadian rhythms that were followed by rhythms in their respective protein levels; the acrophases for the two rhythms were reached at 04:00 and 05:00 hr, respectively. Pinealectomy blunted the rhythms in both m RNA s and protein levels. In contrast, m RNA and protein levels of nuclear receptor ROR α increased significantly after pinealectomy. The cycles of the latter receptor also exhibited circadian rhythms which peaked at 03:00 and 03:45 hr, respectively. Melatonin administration (10–200 mg/kg) increased in a dose‐dependent manner the protein content of MT 1/ MT 2 receptors, with no effects on RORα. Lunzindole treatment, however, did not affect melatonin receptor expression or content of either the membrane or nuclear receptors. Together with previously published findings which demonstrated the intracellular distribution of melatonin in rat liver, the current results support the conclusion that the circadian rhythms of MT 1/MT2 and RORα receptors are under the control of the serum and intracellular melatonin levels. Moreover, the induction of MT 1/ MT 2 receptors after the administration of high doses of melatonin further suggests that the therapeutic value of melatonin may not be restricted to only low doses of the indoleamine.