A homologous radioimmunoassay for rat insulin-like growth factor-I (IGF-I): implications for studies of human IGF-I physiology.
We report the development of a unique radioimmunoassay (RIA) for rat insulin-like growth factor-I (rIGF-I) which does not recognize human IGF-I (hIGF-I). The rIGF RIA uses a specific anti-rIGF-I antiserum with rIGF-I standards and radioligand. Rat sera were extracted by either an abbreviated acid/ethanol procedure or by acid-chromatography with virtually identical results. Assay sensitivity is congruent to 0.5 ng/tube and inter- and intra-assay coefficients of variation were 3.4-7.6% and 4.8-9.2%, respectively. Comparisons of the rIGF-I RIA with a typical heterologous RIA shows that the latter underestimates rIGF-I levels congruent to of 3-fold. Sera from rats treated with hIGF-I were also studied using the rIGF-I RIA and a hIGF-I- specific immunoradiometric assay (IRMA), and results indicate poor correlation between the actual total IGF-I levels (rIGF-I RIA + hIGF-IRMA) and the heterologous RIA estimates. The availability of both rIGF-I and hIGF-I specific immunoassays facilitates more precise studies of hIGF-I in the rat model.
Lee
P D
PD
Department of Pediatrics, Stanford University Medical Center, CA 94305, USA.
Baker
B K
BK
Liu
F
F
Kwan
E Y
EY
Hintz
R L
RL
D000818:Animals; D006224:Cricetinae; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007335:Insulin-Like Growth Factor II / Q000032:analysis; D051379:Mice; D011863:Radioimmunoassay / Q000379:methods* / Q000706:statistics & numerical data; D051381:Rats; D012680:Sensitivity and Specificity; D013045:Species Specificity
D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II