The increase in IGF-1 gene expression following unilateral nephrectomy (UNX) in adult rats is controversial. In this study we have examined whether developmental differences exist in the effect of UNX on IGF-1 gene expression. Immature (23 days) and adult (4 months) Wistar rats underwent a sham operation or left UNX, and were sacrificed 24 or 48 hrs later. IGF-1 mRNA levels were determined in left (control) and right (compensated) kidneys using solution hybridization/RNase protection assays. By 48 hrs post-UNX, remnant kidneys had grown -20±1% in adult rats (P<0.05), and 69±5% in immature rats (P<0.05). IGF-1 mRNA levels were not increased in the adult compensated kidneys at either 24 or 48 hrs post-UNX. In contrast, kidneys from immature rats 24 and 48 hrs post-UNX had an average 4-fold increase (P<0.05) in exon 1 IGF-1 mRNA levels, and an average 3fold increase (P<0.05) in exon 2 mRNA levels. Thus, these findings suggest that there is an age-dependent difference in the effects of UNX on IGF-1 gene expression, and provide the first evidence that IGF-1 gene expression increases following unilateral nephrectomy in immature rats.
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