Response of the insulin-like growth factor system to vitamin A depletion and repletion in rats.
Vitamin A (VA) and insulin-like growth factors (IGF) are important regulators of a wide range of physiological processes. To investigate the IGF system's involvement in the physiological actions of VA, we examined the effects of VA status on components of the IGF system in rats. Male rats (3-wk-old) fed a VA-deficient diet for 11 wk developed VA deficiency, as confirmed by the depletion of serum retinol and hepatic retinyl palmitate. Rats fed the VA-deficient diet had significantly lower body weight (p < 0.05) and lower serum IGF-I concentrations than the rats fed the control diet. The decreases in serum IGF-I levels were accompanied by approximately 40% lower levels of the IGF-I mRNA in the liver and lungs. With respect to the gene expression of other IGF system components, VA deficiency caused a twofold induction of IGF-I receptor (IGF-IR) mRNA in the heart and a twofold reduction in IGFBP-6 mRNA in the lungs, but did not alter the expression of IGF-II, IGFBP-1, IGFBP-3, IGFBP-4 or IGFBP-5 in all tissues examined. When VA-deficient rats received a single injection of retinoic acid (2 mg/rat), tissue IGF-I and IGF-IR gene expression did not change after 4 or 8 h, while the expression of IGF-II, IGFBP-4, and IGFBP-6 mRNAs in some tissues increased rapidly. These results suggest a possible involvement of the IGF system in mediating the physiological actions of VA, including VA-supported growth, in the rat.
Fu
Zhengwei
Z
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1. Bunkyo-ku, Tokyo 113-8657, Japan.
Yoneyama
Miyako
M
Noguchi
Tadashi
T
Kato
Hisanori
H
D000818:Animals; D015152:Blotting, Northern; D004224:Diterpenes; D005786:Gene Expression Regulation; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D000084562:Retinyl Esters; D013002:Somatomedins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution; D014212:Tretinoin / Q000378:metabolism; D014801:Vitamin A / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism*; D014802:Vitamin A Deficiency / Q000235:genetics / Q000378:metabolism*
D004224:Diterpenes; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D000084562:Retinyl Esters; D013002:Somatomedins; D014801:Vitamin A; C014794:retinol palmitate; D014212:Tretinoin