Secretion of insulin-like growth factor-II into bile of rats of different ages.
Bile from rats of different ages (suckling 10-12 days; weanling 30-33 days, and adult 60-70 days) was collected and studied for the presence of immuno- and receptor-assayable insulin-like growth factor-II (IGF-II) concentrations. Concentrations of RIA IGF-II in bile were highest in suckling rats (230 +/- 38 ng/ml) and lowest in adults (47 +/- 7 ng/ml). These concentrations were approximately twice those of the bile IGF-I concentration in sucklings, as measured in a previous study. Selected bile samples were also assayed using a competitive binding assay with a crude preparation of adult rat liver membranes bearing the IGF-II receptor. These studies confirmed the presence of receptor- (as well as immuno-) active IGF-II in bile. Since bile flow rates increased dramatically after the suckling period, bile delivery rates of IGF-II were normalized as picograms per gram body weight per hour. When such calculations were done, bile IGF-II delivery rates to the small intestine were highest in sucklings and weanlings in comparison to adult rats. Thus non-enterically derived (milk- and bile-borne) IGF-II delivery to the suckling small intestine can be approximated at roughly 1 microg/day. Unlike IGF-I, intravenously injected IGF-II could not be detected in suckling bile, suggesting a predominantly hepatic origin. From this study we conclude that there exists a significant delivery of receptor-active IGF-II to the gastrointestinal tract of rats of all ages.
Philipps
A F
AF
Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona College of Medicine, Tucson, Ariz., USA. a.philipps@ucdmc.ucdavis.edu
Dvorák
B
B
Anderson
G G
GG
Grille
J G
JG
Williams
C S
CS
Koldovský
O
O
D000375:Aging; D000818:Animals; D000833:Animals, Suckling; D001646:Bile / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007275:Injections, Intravenous; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007335:Insulin-Like Growth Factor II / Q000008:administration & dosage / Q000032:analysis / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D014886:Weaning
D017527:Receptor, IGF Type 2; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II