Evidence of a role for melatonin in fetal sheep physiology: direct actions of melatonin on fetal cerebral artery, brown adipose tissue and adrenal gland. The Journal of physiology [J Physiol] Journal article | | Title | Evidence of a role for melatonin in fetal sheep physiology: direct actions of melatonin on fetal cerebral artery, brown adipose tissue and adrenal gland. | | Author(s) | Torres-Farfan C, Valenzuela FJ, Mondaca M, Valenzuela GJ, Krause B, Herrera EA, Riquelme R, Llanos AJ, Seron-Ferre M | | Institution | Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile. | | Source | J Physiol 2008 Jul 3. | | Abstract | Although the fetal pineal gland does not secrete melatonin, the fetus is exposed to melatonin of maternal origin. In the non-human primate fetus, melatonin acts as a trophic hormone for the adrenal gland, stimulating growth while restraining cortisol production. This latter physiologic activity, lead us to hypothesize that melatonin may influence some fetal functions critical for neonatal adaptation to extrauterine life. To test this hypothesis we explored i) the presence of G-protein coupled melatonin binding sites and ii) the direct modulatory effects of melatonin on norepinephrine induced middle cerebral artery (MCA) contraction, brown adipose tissue (BAT) lypolisis and ACTH induced adrenal cortisol production in fetal sheep. We found that melatonin directly inhibits the response to norepinephrine in the MCA and BAT, and also inhibits the response to ACTH in the adrenal gland. Melatonin inhibition was reversed by the melatonin antagonist luzindole only in the fetal adrenal. MCA, BAT and adrenal tissue displayed specific high affinity melatonin binding sites coupled to G-protein (Kds; MCA 64.1 +/- 9.8; BAT 44.2 +/- 12.4 and adrenal 123.3 +/- 22.9 pM). Melatonin binding was displaced by luzindole only in the adrenal gland, supporting that action in the MCA and BAT is mediated by different melatonin receptors. These direct inhibitory responses to melatonin support a role for melatonin in fetal physiology, which we propose prevents major contraction of cerebral vessels, restrains cortisol release and restricts BAT lypolisis during fetal life. | | Language | ENG | | Pub Type(s) | JOURNAL ARTICLE
| | PubMed ID | 18599539 |
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