title: Variation of tyrosine aminotransferase expression during the day in rats of different ages.
abstract: The activity of the enzyme tyrosine aminotransferase and the synthesis of its specific mRNA were evaluated at different hours of the day in the liver of 3-, 12- and 24-month old BN rats. The enzyme activity has a circadian rhythm with a peak at midnight in 3- and 12-month old, which shifts to 03.00 hrs in 24-month old animals, in agreement with previous results. The expression of TATmRNA also changes during the day indicating circadian fluctuations which change with age. In 3-month old rats the TATmRNA peak is at 19.00 hrs, preceding that of the enzyme activity. In 12-month old rats the TATmRNA synthesis reaches a maximum at midnight and in 24-month old rats at 03.00 hrs. The results show that the circadian rhythm of tyrosine aminotransferase activity is due to a different gene expression throughout the day, which is influenced by age.
authors.affiliation: Istituto di Patologia Generale, Università degli Studi di Perugia, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Servillo
authors.forename: M A
authors.initials: MA
authors.lastname: Della Fazia
authors.forename: M
authors.initials: M
authors.lastname: Viola-Magni
mesh_terms: D000375:Aging; D000818:Animals; D002940:Circadian Rhythm; D015971:Gene Expression Regulation, Enzymologic; D008099:Liver / Q000201:enzymology / Q000254:growth & development*; D008297:Male; D011061:Poly A / Q000235:genetics / Q000302:isolation & purification; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D011914:Rats, Inbred BN; D014444:Tyrosine Transaminase / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D011061:Poly A; D012313:RNA; D014444:Tyrosine Transaminase