title: Photic regulation of melatonin in rat retina and the role of proteasomal proteolysis.
abstract: Several investigations have shown that illumination at night reduces melatonin level in the mammalian pineal, but the effect of night illumination on the retina is not known. In this study retinas were cultured in a flow-through apparatus and then were exposed to light at ZT 18. Light exposure reduced melatonin levels to the daytime level within 30 min. The reduction of melatonin levels was due to a rapid decrease in the activity of the enzyme AA-NAT; AA-NAT mRNA levels were not affected by illumination. Pre-incubation with lactacystin (25 microM) prevented light-induced reduction of AA-NAT activity and melatonin levels. These results demonstrate that melatonin levels in the mammalian retina are affected by light exposure at night, via proteosomal proteolysis of AA-NAT.
authors.affiliation: Neuroscience Institute, Morehouse School of Medicine, 720 Westview Drive, SW, Atlanta, GA 30310-1485, USA.
authors.forename: C
authors.initials: C
authors.lastname: Fukuhara
authors.forename: J C
authors.initials: JC
authors.lastname: Dirden
authors.forename: G
authors.initials: G
authors.lastname: Tosini
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology; D003546:Cysteine Endopeptidases / Q000378:metabolism / Q000528:radiation effects*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D008297:Male; D008550:Melatonin / Q000096:biosynthesis / Q000528:radiation effects*; D009097:Multienzyme Complexes / Q000378:metabolism / Q000528:radiation effects*; D010447:Peptide Hydrolases / Q000378:metabolism / Q000528:radiation effects*; D010775:Photic Stimulation; D046988:Proteasome Endopeptidase Complex; D012333:RNA, Messenger / Q000378:metabolism / Q000528:radiation effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects*
chemical_list: D015853:Cysteine Proteinase Inhibitors; D009097:Multienzyme Complexes; D012333:RNA, Messenger; C067713:lactacystin; D001191:Arylamine N-Acetyltransferase; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008550:Melatonin; D000111:Acetylcysteine