Adenosine receptors that modulate adenylate cyclase activity have been identified recently in a number of tissues. The purpose of these investigations was to determine the effect of adenosine on ion transport in rabbit ileum in vitro. Adenosine and some of its analogues were found to increase the short circuit current (Isc) and the order of potency was N-ethylcarboxamide-adenosine greater than or equal to 2-chloroadenosine greater than phenylisopropyladenosine greater than adenosine. Purine-intact adenosine analogues had no effect on Isc. The effect of adenosine on Isc was enhanced by deoxycoformycin, an adenosine deaminase inhibitor, and by dipyridamole, an adenosine uptake inhibitor. The increase in Isc induced by 2-chloroadenosine was partially reversed in a dose-dependent manner by 8-phenyltheophylline but not by theophylline or isobutylmethylxanthine. 2-Chloroadenosine increased cyclic AMP content, and stimulated net Cl secretion; these effects were partially blocked by 8-phenyltheophylline. These results suggest that there is an adenosine receptor on rabbit ileal mucosal cells that stimulates adenylate cyclase, which results in secondary active Cl secretion.
J W Dobbins, J P Laurenson, J N Forrest Jr