Gastrointestinal control of sodium excretion in sodium-depleted conscious rabbits

Recent studies of sodium-depleted rabbits have shown that oral sodium loading is followed by greater natriuresis than intravenous sodium loading. The present study was undertaken to determine if this is dependent on differences in aldosterone excretion. Rabbits in balance on a low-sodium diet were given bolus doses of sodium either orally or intravenously. Those receiving oral sodium responded with a greater natriuresis than those receiving it intravenously. No differences in aldosterone excretion were demonstrated after oral or intravenous sodium repletion. Rabbits given large doses of exogenous aldosterone continued to excrete more sodium after oral than after intravenous repletion. This study demonstrates that in rabbits the gastrointestinal tract functions to regulate renal sodium excretion and that the mechanism is independent of aldosterone.