title: Adaptive responses of 25-hydroxyvitamin D3 1-alpha hydroxylase expression to dietary phosphate restriction in young and adult rats.
abstract: Regulation of vitamin D metabolism alters with age. The present study is undertaken to investigate if the loss of renal 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) production in response to dietary phosphate (P) restriction in adult rats is due to an alteration in the renal expression of 25-hydroxyvitamin D(3) 1-alpha hydroxylase (1-OHase). Young (4-6 weeks old) and adult (12-14 weeks old) male Sprague Dawley rats were fed either normal P (NPD) or low P diet (LPD) for 0-5 days. Basal expression of 1-OHase protein was higher in adult rats. Young rats, but not adult rats, significantly increased 1-OHase protein and mRNA expressions in response to LPD in a time-dependent manner. To determine if the stability of renal 1-OHase protein changes with LPD feeding, young and adult rats fed either NPD or LPD for 5 days were injected intravenously with cycloheximide (CHX), a protein synthesis inhibitor. CHX decreased 1-OHase protein expression in young rats fed NPD. However, CHX did not alter 1-OHase protein expression in young rats fed LPD nor in adult rats fed either diet. The results indicate that the stability of renal 1-OHase protein increased with age and that LPD increased its stability only in young rats.
authors.affiliation: Central Laboratory of the Institute of Molecular Technology for Drug Discovery and Synthesis, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China.
authors.forename: Wan-Ping
authors.initials: WP
authors.lastname: Lai
authors.forename: Tsui-Shan
authors.initials: TS
authors.lastname: Chau
authors.forename: Pik-Yuen
authors.initials: PY
authors.lastname: Cheung
authors.forename: Wen-Fang
authors.initials: WF
authors.lastname: Chen
authors.forename: Samuel Chun-Lap
authors.initials: SC
authors.lastname: Lo
authors.forename: Murray J
authors.initials: MJ
authors.lastname: Favus
authors.forename: Man-Sau
authors.initials: MS
authors.lastname: Wong
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism*; D000375:Aging / Q000378:metabolism; D000818:Animals; D003677:Deficiency Diseases / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology / Q000378:metabolism; D008297:Male; D010710:Phosphates / Q000172:deficiency* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D010710:Phosphates; D012333:RNA, Messenger; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase