EFFECT OF FETAL NEPHRECTOMY ON INSULIN-LIKE GROWTH-FACTORS AND THEIR BINDING-PROTEINS IN SHEEP

Bilateral nephrectomy retards fetal growth and decreases somatomedin ( insulin-like growth factor-I, IGF-I) activity. To determine whether ne phrectomy alters the synthesis of IGF-I or its binding proteins (IGFBP s), we studied 6 sets of twin fetuses. Kidneys were removed bilaterall y from 1 twin of each set at 112-122 days of gestation (term 145 days) . Plasma IGF-I concentrations were greater in nephrectomized fetuses t han in the intact twins during the 1st week (261 +/- 35 vs. 153 +/- 21 ng/ml, p < 0.02; mean +/- SE) but not the 2nd week after surgery. Nep hrectomy increased the abundance of the IGFBPs to levels 2-3 times gre ater than those in intact twins. Fetal hepatic IGFBP1 mRNA levels incr eased in 4 of 6 nephrectomized fetuses, while those of IGF-I, IGF-II, IGFBP2 were unchanged. Nephrectomy markedly alters the abundance of IG F-I and IGFBPs in plasma probably through mechanisms unrelated to synt hesis.