The developmental pattern of rabbit brain insulin and insulin-like growth factor receptor expression

To examine the effect of development on rabbit brain insulin and insulin-like growth factor (IGF) receptor expression, we characterized and quantitated receptor mRNAs by Northern blot analysis and affinity-labeled ligand bound receptors by SDS-PAGE and autoradiography. At various stages of development ranging from 23 to 30 day gestational (term approximately 31 days), 1 to 10 day postnatal ages and the adult, no change in the whole brain insulin receptor mRNA (7.0, 6.0 and 5.5 kb) and affinity-labeled receptor protein (approximately 125 kDa) levels was observed. The IGF-I receptor mRNA (11.5, 6.5 and 4.5 kb) and affinity-labeled receptor (approximately 125 kDa) protein levels declined during the neonatal stages of development. In the case of the IGF-II receptor, while the mRNA levels (9.0 and 4.5 kb) remained constant, the corresponding affinity-labeled receptor protein (approximately 230 kDa) declined with maturation. We conclude that a differential regulation of brain insulin, IGF-I and IGF-II receptor expression occurs during development.