Dopamine stimulation of active Na and Cl absorption in rabbit ileum

testinal ion transport have been evaluated. An epithe-lial sheet preparation of rabbit ileum was used in vitro with the Ussing chamber-voltage clamp technique. Dopamine, in the presence of 1 mM ascorbic acid, added to the serosal bathing solution caused a dose-dependent decrease in short-circuit current, with a half-maximal effect at 1.2 MM and maximal effect of-50 uA/cm2 at 50,M; dopamine decreased the po-tential difference, and increased the conductance and net Na and net Cl absorption. There was no effect on the residual ion flux. Dopamine did not alter the change in short-circuit current caused by mucosal glu-cose (10 mM) or serosal theophylline (10 mM). Mucosal dopamine had no effect. The effect of dopamine on short-circuit current was inhibited by the dopamine antagonists haloperidol and domperidone and the a2-adrenergic antagonist yohimbine; there was no effect of the a,-antagonist prazosin and the,3-antagonist pro-pranolol. In addition, the a2-adrenergic agonist clon-idine, but not the cal-agonist methoxamine caused a dose-dependent decrease in short-circuit current. The ileal effects of dopamine did not occur via conversio