Effect of paraformaldehyde fixation on localization and characterization of insulin‐like growth factor‐I (IGF‐I) receptors in the rat brain

摘要

AbstractIn order to design an approach for localizing IGF‐I receptors within the intact CNS, the effect of paraformaldehyde (PAF) fixation on receptor binding was examined. Cryostat sections of rat brains, which were perfused with O to 10% PAF, were incubated in125I‐IGF‐I and assayed for binding under equilibrium conditions. Binding was quantified from 10 brain regions, involving laminae and nuclei from median eminence, thalamus, hippocampus, choroid plexus, pyriform cortex, and cerebral cortex, by computer densitometry of film autoradiographs. The specific binding, saturation curves, Bmaxand Ka, ligand specificity, and binding reversibility of IGF‐I binding sites were not significantly affected by 1% or 2% PAF. However, 4% PAF elevated IGF‐I receptor total binding, nonspecific binding, and Ka, and decreased Bmax, presumably by increasing the number of tissue‐receptor interconnections, Only nonspecific125I‐IGF‐I binding persisted when 10% PAF was used. These results indicate that tissue perfused with 2% PAF can be used for localizing IGF‐I receptors by autoradiographi