Secretion of insulin-like growth factor-II into bile of rats of different ages

Biol Neonate. 2000;78(2):106-12. doi: 10.1159/000014258.

Abstract

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aging*
  • Animals
  • Animals, Suckling
  • Bile / chemistry
  • Bile / metabolism*
  • Humans
  • Injections, Intravenous
  • Insulin-Like Growth Factor I / analysis
  • Insulin-Like Growth Factor II / administration & dosage
  • Insulin-Like Growth Factor II / analysis
  • Insulin-Like Growth Factor II / metabolism*
  • Radioimmunoassay
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, IGF Type 2 / metabolism
  • Weaning

Substances

  • Receptor, IGF Type 2
  • Insulin-Like Growth Factor I
  • Insulin-Like Growth Factor II