Characterization of hepatic epidermal growth factor receptors in the developing rat.
Binding of 125I-labeled epidermal growth factor (EGF) was characterized in basolateral plasma membranes prepared from the livers of 21-day gestation fetuses, 14-day-old sucklings and adult Sprague-Dawley rats using a self-generating Percoll gradient method. The membrane preparations employed have been previously assayed in terms of plasma membrane protein yield, enrichment of various marker enzymes and sodium-dependent bile acid and amino acid transport. 125I-EGF binding was saturable and time and temperature dependent. Equilibrium analyses showed that the suckling period is characterized by a marked decrease in overall hepatic EGF binding capacity (460 +/- 50 fmol/mg protein) compared to either the fetal period (1290 +/- 160 fmol/mg) or to adults of either sex (males = 1540 +/- 230, females 1010 +/- 130 fmol/mg). Treatment of the suckling rat with parenteral EGF resulted in a 78% reduction in the observed binding capacity when assessed 2 h after growth factor administration. Comparison of binding affinities revealed no significant difference between the suckling and adult preparations (Kd = 0.40 +/- 0.03 vs. 0.39 +/- 0.02 nM, respectively); however, both preparations differed significantly from the fetal group which exhibited a decreased affinity of binding with a higher overall dissociation constant (Kd = 0.68 +/- 0.06 nM). Thus, it appears that major ontogenetic changes occur in the rat hepatic ligand/receptor system for epidermal growth factor. These changes are discussed in the context of transitional events in mammalian development such as birth and weaning.
D000818:Animals; D000833:Animals, Suckling / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012727:Sex Characteristics
D004815:Epidermal Growth Factor; D066246:ErbB Receptors