Dissociation of bone mineral density from age-related decreases in insulin-like growth factor-I and its binding proteins in the male rat.
We evaluated the possibility that age-related decreases in circulating and/or bone-associated insulin-like growth factor-I (IGF-I) and its binding proteins (BPs) were associated with the development of osteopenia in 8-, 16-, and 24-month-old specific pathogen-free Brown Norway/Fischer 344 male rats. We measured bone mineral densities (BMD) of femurs by dual-energy x-ray absorptiometry. IGFs and IGFBPs were extracted from bone and separated by molecular exclusion HPLC before quantitation by specific radioligand assays. BMD did not change significantly between 8 and 24 months of age. IGF-I levels decreased by about 30% between 8 and 24 months in both serum and bone. Similarly, both circulating and bone-derived IGFBPs also declined (30% and 60%, respectively) with age. Thus, maintenance of femoral BMD throughout most of the adult rat life span was dissociated from the age-related decline in circulating and bone-associated IGF-I and IGFBPs.
Benedict
M R
MR
Department of Pediatrics, SUNY Health Science Center at Syracuse.
Adiyaman
S
S
Ayers
D C
DC
Thomas
F D
FD
Calore
J D
JD
Dhar
V
V
Richman
R A
RA
D000375:Aging / Q000378:metabolism*; D000818:Animals; D015519:Bone Density / Q000502:physiology*; D001851:Bone Diseases, Metabolic / Q000209:etiology / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism; D002352:Carrier Proteins / Q000097:blood / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D013047:Specific Pathogen-Free Organisms
D002352:Carrier Proteins; D007334:Insulin-Like Growth Factor I