Intestinal transport of water, sodium & glucose from an electrolyte solution with & without bicarbonate

In this study we have evaluated the role of bicarbonate on water and sodium transport in normal and secreting ilea of rabbits as controversy exists regarding the inclusion of bicarbonate in oral rehydration solution (ORS). In anaesthetized rabbits 10 cm closed ileal loops were constructed and filled with 5 ml of an electrolyte solution with and without bicarbonate, which contained polyethylene glycol (PEG; mol wt 4,000) as a non-absorbable marker. The fluid was withdrawn after an hour and analyzed for PEG, sodium and glucose. Similar studies were carried out in loops one hour after exposure to 1 microgram/ml of purified cholera toxin. Body temperature was maintained at 37 degrees C during the experiment by using a lamp. The mean +/- SE of water and sodium absorption, with bicarbonate versus without bicarbonate, was -1.4 +/- 0.1 vs -1.1 +/- 0.3 ml/h/10 cm, and -340.8 +/- 23.0 vs -308.4 +/- 35.6 mM/h/10 cm, respectively from secreting rabbit ilea. A similar effect was observed in normal ilea. It is concluded that bicarbonate containing electrolyte solution has no additional promoting effect on water and sodium absorption in normal or secreting ilea of rabbits.