title: Response of tyrosine hydroxylase and GTP cyclohydrolase I gene expression to estrogen in brain catecholaminergic regions varies with mode of administration.
abstract: The effect of different dose, mode and duration of estradiol administration was examined in the different brain catecholaminergic areas in ovariectomized (OVX) female rats. We determined changes in mRNA levels of tyrosine hydroxylase (TH), rate-limiting enzyme in catecholamine (CA) biosynthesis of GTP cyclohydrolase I (GTPCH), rate-limiting enzyme in biosynthesis as well as of tetrahydrobiopterin (BH4), and concentration of BH4, which is an essential cofactor for TH, tryptophan hydroxylase and nitric oxide synthase. Short-term administration of estradiol benzoate (EB) by five injections of 15 or 40 microg/kg 12 h apart led to increase in TH and GTPCH mRNA levels in dopaminergic and noradrenergic cell bodies of the ventral tegmental area (VTA), substantia nigra (SN), locus coeruleus (LC) and the nucleus of solitary tract (NTS) depending on dose of administration. Estrogen-elicited alterations in BH4 concentrations were mostly correlated with changes in GTPCH mRNA levels, except in SN. Long-term administration of estradiol by injections (EB: 25 microg/kg, 16 injections 26 h apart; 50 microg/kg, 16 injections 48 h apart) or pellets (0.1 mg 17 beta-estradiol, 14 days) were not very effective in modulating mRNA levels for both genes in most locations except the NTS. Long-term injections of EB elevated GTPCH mRNA levels throughout the NTS and in microvessels. Administration of estradiol by pellets led to decline of TH mRNA in rostral-medial and elevation in caudal parts of the NTS. Thus, estradiol has a complex and differential effect on TH and GTPCH gene expression in a tissue specific manner and depends on the mode of administration.
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Lidia I
authors.initials: LI
authors.lastname: Serova
authors.forename: Shreekrishna
authors.initials: S
authors.lastname: Maharjan
authors.forename: An
authors.initials: A
authors.lastname: Huang
authors.forename: Dong
authors.initials: D
authors.lastname: Sun
authors.forename: Gabor
authors.initials: G
authors.lastname: Kaley
authors.forename: Esther L
authors.initials: EL
authors.lastname: Sabban
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000097:blood / Q000502:physiology; D005260:Female; D006136:GTP Cyclohydrolase / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D007279:Injections, Subcutaneous; D008125:Locus Coeruleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008636:Mesencephalon / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017552:Solitary Nucleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013378:Substantia Nigra / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D014018:Tissue Distribution; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism*; D017557:Ventral Tegmental Area / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: D002395:Catecholamines; D004343:Drug Implants; D012333:RNA, Messenger; C074283:estradiol 3-benzoate; D001708:Biopterins; D004958:Estradiol; D014446:Tyrosine 3-Monooxygenase; D006136:GTP Cyclohydrolase; C003402:sapropterin; D004298:Dopamine; D009638:Norepinephrine