Ontogeny of hepatic type I insulin-like growth factor receptors in the rat.
We studied the pre- and postnatal developmental regulation of the hepatic type I IGF receptor in the rat. Fetal rat liver membranes bound IGF-I throughout the latter part of gestation (d 17 to 21). After birth, binding diminished rapidly, reaching barely detectable levels by the 13th postnatal d. However, the presence of type I IGF receptors was readily demonstrated by affinity-labeling throughout the immediate postnatal period and in adult rats. Furthermore, IGF-I-dependent autophosphorylation of type I receptors could be seen in both fetal and adult liver membranes. Fasting for 48 h in adult rats led to a 2- to 3-fold increase in affinity-labeled type I IGF receptors. In contrast, nutrient deprivation to the fetus, via maternal fasting, did not alter fetal hepatic IGF-I binding or affinity-labeling of the type I receptor. These results support a role for the IGF and the type I IGF receptor in the autocrine/paracrine regulation of hepatic growth through the latter stages of gestation in the rat. The demonstration of enzymatically active type I IGF receptors in adult liver, and their increased expression in fasted adult rats is consistent with an autocrine/paracrine role for hepatic IGF-I in the adult.
Gruppuso
P A
PA
Section of Biochemistry, Brown University, Providence, Rhode Island.
Walker
T D
TD
Carter
P A
PA
D000345:Affinity Labels; D000818:Animals; D005215:Fasting; D005260:Female; D005333:Fetus / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D010766:Phosphorylation; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017451:Receptors, Somatomedin
D000345:Affinity Labels; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D007334:Insulin-Like Growth Factor I