AJP - Gastrointestinal and Liver Physiology, Vol 253, Issue 3 330-G335, Copyright © 1987 by American Physiological Society
Effect of systemic acid-base balance on ileal secretion
D. S. Goldfarb, P. M. Ingrassia and A. N. Charney
We previously reported that systemic pH and HCO3 concentration affect ileal
water and electrolyte absorption. To determine whether these effects could
influence an ongoing secretory process, we measured transport in ileal
loops exposed to either saline or 50-75 micrograms cholera toxin in
mechanically ventilated Sprague-Dawley rats anesthetized with pentobarbital
sodium. The effects of acute respiratory and metabolic acidosis and
alkalosis were then examined. Decreases in systemic pH during respiratory
acidosis caused equivalent increases in net water (54 +/- 8 microliters .
cm-1 . h-1) and Na absorption (7 +/- 1 mu eq . cm- . h-1) and smaller
increases in Cl absorption in cholera toxin compared with saline loops.
These increases reversed the net secretion of these ions observed during
alkalemia in the cholera toxin loops to net absorption. Metabolic acidosis
and alkalosis and respiratory compensation of systemic pH of these
metabolic disorders also altered cholera toxin-induced secretion in a
direction consistent with the pH change. The increase in net HCO3 secretion
caused by cholera toxin was unaffected by the respiratory disorders and did
not vary with the HCO3 concentration in the metabolic disorders. These
findings suggest that the systemic acid-base disorders that characterize
intestinal secretory states may themselves alter intestinal absorptive
function and fluid losses.
