title: Insulin-like growth factor-I in the plasma of two reptiles: assay development and validations.
abstract: Radioimmunoassays (RIAs) of insulin-like growth factor-I (IGF-I) in nonmammals are complicated by two problems: decreased specificity due to heterologous assays and assay interference from IGF binding proteins. We have developed and validated an RIA for the detection of IGF-I in reptilian plasma that circumvents these problems. Biochemical validations show parallelism between standard curves, plasma dilutions, and internal standards. Further, biological validations indicate that (1) plasma IGF-I levels are significantly reduced in nonreproductive, female American alligators (Alligator mississippiensis) with high plasma estradiol-17 beta concentrations compared to individuals with low plasma estradiol-17 beta concentrations and (2) plasma IGF-I concentrations are elevated in juvenile Trachemys scripta elegans turtles fed higher quality diets (defined by protein and energy content). These results provide impetus for future studies of IGF-I in reptiles.
authors.affiliation: Department of Zoology, University of Florida, Gainesville 32611, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Crain
authors.forename: T S
authors.initials: TS
authors.lastname: Gross
authors.forename: M C
authors.initials: MC
authors.lastname: Cox
authors.forename: L J
authors.initials: LJ
authors.lastname: Guillette
mesh_terms: D000489:Alligators and Crocodiles / Q000097:blood*; D000818:Animals; D015153:Blotting, Western; D004958:Estradiol / Q000097:blood; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D011863:Radioimmunoassay / Q000592:standards / Q000706:statistics & numerical data*; D012680:Sensitivity and Specificity; D014426:Turtles / Q000097:blood*
chemical_list: D004958:Estradiol; D007334:Insulin-Like Growth Factor I