Factors affecting mucosal water and sodium transfer in everted sacs of rat jejunum.

1. Mucosal water and sodium transfer were measured in everted sacs of rat jejunum.2. There was no effect on mucosal water and sodium transfer when aldosterone was added to the incubation medium.3. An 87% increase in mucosal water and sodium transfer was obtained in sacs prepared from animals maintained on a low sodium diet compared to sacs from animals on a normal diet.4. Injection of 5 mug aldosterone intraperitoneally to animals maintained on a high sodium diet produced a significant increase in mucosal water and sodium transfer in sacs prepared 27 hr later and this was still present 36 hr after injection.5. The aldosterone-induced rise in mucosal water transfer was blocked if actinomycin D was administered one hour before the aldosterone injection.6. It is suggested that aldosterone action on sodium and water transport in rat jejunum is mediated through a primary action on protein synthesis and that the long delay can be explained in terms of gut morphology.