Normal values of circulating insulin-like growth factor-I bioactivity in the healthy population: Comparison with five widely used IGF-I immunoassays

摘要

In the circulation, IGF-I is bound to six different IGF-bind-ing proteins (IGFBPs) which interfere with common immunoassays and must be removed before the measurement. But large differences are also observed between the different immunoassays available. The IGFBPs regulate the bioavailability and the reaction of IGF-1 with its receptor. A kinase receptor activation assay (KIRA, Am J Physiol Endocrinol Metab 2003; 284: E1149-E1155) quantifies the phosphorylation of tyrosine of the activated IGF-I receptor (IGF-IR) in embryonic renal cells using an anti-phosphoty-rosine antibody as tracer (interassay CV 6.8 to 12.6%).