Espace extracellulaire, perméabilité à l'inuline et accumulation de L-alanine dans l'intestin isolé de Grenouille

In order to calculate the intracellular concentration of accumulated L-alanine, the extracellular space (inulin-14C) of frog intestine was measured. To check the validity of the technique, frog liver and gastrocnemius were used too. By scraping proximal portions of intestine, the inulin space was found to be similar (around 20% of total tissue water) in both the muscle layer and the mucosa. The mucosal epithelium is an imperfect barrier to inulin while the serosa is very permeable. These results suggest that the interstitial solute concentration is best approximated by equating it to that of the serosal solution. The in vitro inulin space, compared to the in vivo one, increases with time, as does the cellular hydration. The data obtained from measurements of extracellular space and from L-alanine uptake show that the intracellular amino acid is in a free state.