Differences in the association of insulin-like growth factor-I (IGF-I) and IGF-I variants with rat, sheep, pig, human and chicken plasma-binding proteins.
Associations between labelled insulin-like growth factors (IGFs) and IGF-binding proteins in plasma have been compared in the rat, sheep, human, pig and chicken. The IGFs tested were recombinant human IGF-I, the truncated variant, des(1-3)IGF-I, and LR3IGF-I, an extended form that had been engineered so as to minimize interactions with IGF-binding proteins. Marked species differences were demonstrated, notably that the IGF-I variants which exhibited extremely weak binding in rat plasma bound significantly in plasma from the other species. This result was shown both by size-exclusion chromatography of labelled IGFs added to plasma, in which the extent of variant IGF-I binding decreased in the order sheep > human > pig = chicken > rat, and by competition for labelled IGF-I binding in vitro, in which the order was pig = chicken > sheep > human > rat. Notwithstanding these differences, the two IGF-I variants showed only slight between-species binding differences when tested with purified rat, sheep and human IGF-binding protein-3. Ligand blotting experiments with plasma from the five species similarly showed a consistent pattern in that IGF-I binding was much greater than des(1-3)IGF-I binding, which in turn was greater than LR3IGF-I binding.(ABSTRACT TRUNCATED AT 250 WORDS)
Lord
A P
AP
Child Health Research Institute, North Adelaide, South Australia.
Bastian
S E
SE
Read
L C
LC
Walton
P E
PE
Ballard
F J
FJ
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002645:Chickens; D002845:Chromatography; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D012756:Sheep; D013045:Species Specificity; D013552:Swine
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; C084339:LR(3)IGF-I; D010446:Peptide Fragments; C058957:insulin-like growth factor 1, des-(1-3)-; D007334:Insulin-Like Growth Factor I