title: Diurnal variation in growth hormone receptor messenger ribonucleic acid in liver and skeletal muscle of lit/+ and lit/lit mice.
abstract: The present study investigated the diurnal variation in GH receptor (GHR) mRNA in liver and skeletal muscle of 3-month-old GH-deficient and -sufficient mice using quantitative real-time RT-PCR. lit/lit (GH deficient) or lit/+ (GH sufficient) mice were fed ad libitum and lights were on between 0600 and 2000. Tissues were collected at 0800-1000, 1200-1400 and 2000-2200. Hepatic GHR mRNA levels of lit/+ mice at 0800-1000 were significantly lower than those at 1200-1400 and 2000-2200. There was no significant variation in hepatic GHR mRNA of lit/lit mice. In skeletal muscle, GHR mRNA levels of both lit/+ and lit/lit mice at 1200-1400 were significantly higher than those at 0800-1000 and 2000-2200. There was also a diurnal change in hepatic IGF-I mRNA levels of lit/+ but not of lit/lit mice; the levels were lowest at 0800-1000 in lit/+ mice. On the other hand, there was no variation in IGF-I mRNA levels in skeletal muscle. These results suggest that 1) there is a diurnal variation in GHR expression in liver and skeletal muscle and the pattern of the variation is tissue specific; 2) GH deficiency blunted the diurnal variation in GHR mRNA in liver but not that in skeletal muscle; 3) IGF-I mRNA expression in liver is more closely related to GHR mRNA expression than that in skeletal muscle.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: Emina
authors.initials: E
authors.lastname: Itoh
authors.forename: Keiji
authors.initials: K
authors.lastname: Iida
authors.forename: Juan P
authors.initials: JP
authors.lastname: del Rincon
authors.forename: Dong-Sun
authors.initials: DS
authors.lastname: Kim
authors.forename: Michael O
authors.initials: MO
authors.lastname: Thorner
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D013006:Growth Hormone / Q000378:metabolism; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D011986:Receptors, Somatotropin / Q000096:biosynthesis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D007328:Insulin; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone