title: mRNA transcription determines the lag period for the induction of pineal melatonin synthesis in the Syrian hamster pineal gland.
abstract: The nocturnal pattern of Syrian hamster pineal melatonin synthesis is characterized by a 6-8 h lag period, followed by a late-night, short-duration peak in both N-acetyltransferase (NAT) activity and melatonin content. Administration of cycloheximide (20 mg/kg body weight) given either at the time of lights out or 4 h into the dark phase to Syrian hamsters blocked the nocturnal increase in both pineal NAT activity and melatonin content. Actinomycin D (5 mg/kg body weight) prevented the nocturnal increase in both constituents only when it was administered at darkness onset, being significantly less effective when injected after 4 h of dark exposure. Reinduction of melatonin production by isoproterenol (2 mg/kg body weight) administration to acutely light-exposed animals during late darkness was prevented by cycloheximide, but not by actinomycin D administration. The results suggest that whereas Syrian hamster pineal melatonin production requires protein synthesis both early and late in the dark phase, the transcription of a putative NAT-related mRNA, which occurs only during the early night, seems to determine the lag period in melatonin synthesis and pineal responsiveness to beta-adrenergic receptor agonist stimulation.
authors: Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762.
authors: A
authors: A
authors: Gonzalez-Brito
authors: M E
authors: ME
authors: Troiani
authors: A
authors: A
authors: Menendez-Pelaez
authors: M J
authors: MJ
authors: Delgado
authors: R J
authors: RJ
authors: Reiter
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology; D006224:Cricetinae; D003624:Darkness; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D008647:Mesocricetus / Q000378:metabolism / Q000502:physiology*; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000502:physiology; D013997:Time Factors; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D012333:RNA, Messenger; D000123:Acetyltransferases; D008550:Melatonin; D007545:Isoproterenol