Effect of aspirin on normal and cholera toxin-stimulated intestinal electrolyte transport

The effect of aspirin on normal and cholera toxin-stimulated electrolyte transport has been investigated in vitro, because this drug appears to inhibit cholera toxin-induced intestinal secretion in in vivo animal models. In the Ussing chamber, 10 mM aspirin decreased the control rabbit ileal potential difference and short-circuit current by 50% and increased conductance by 28%. Bidirectional electrolyte flux determinations showed that aspirin significantly increased both Na and Cl absorption and reduced flux (which probably represents HCO3 secretion) to zero. This effect of aspirin appears to be identical to that reported to others with catecholamines as determined with similar techniques. However, alpha-adrenergic blockers did not prevent the electrical effects of aspirin, suggesting that aspirin does not have its effect through release of tissue stores of catecholamines. In the presence of aspirin, cholera toxin increased the potential difference and short-circuit current, and decreased the conductance of rabbit ileum in a fashion qualitatively similar to control tissues. However, aspirin reversed cholera toxin-stimulated Na transport from secretion to absorption, inhibited cholera toxin, induced Cl secretion by 58% and partially, but not significantly, inhibited HCO3 secretion. Thus, the inhibitory effect of aspirin on cholera toxin-induced electrolyte secretion appears to be due to aspirin-stimulated Na and Cl absorption. Although aspirin reduced tissue cyclic AMP concentrations in normal and cholera toxin-stimulated ileum, it also inhibited the electrolyte secretion induced by exogenous cyclic AMP. Thus, if aspirin's stimulatory effect on sodium and anion absorption in normal tissue and its inhibitory effect on cholera toxin-stimulated sodium and anion secretion involves a cyclic AMP-mediated system, the effect must be a step distal to cyclic AMP production or degradation. The exact mechanism of aspirin's effect on normal and cholera toxin-induced electrolyte transport, and its possible usefulness in the treatment of cholera diarrhea, remains to be determined.