Evidence for adenosine A1 receptor action in rat jejunal mucosa

Cyclic AMP was elevated in rat jejunal mucosa in the presence of adenosine deaminase (2 mg/1) both alone or under conditions of stimulated mucosal cyclic AMP accumulation (forskolin 20 microM/papaverine 100 microM). The effects of adenosine deaminase were reversed by (-)-N6-phenylisopropyl-adenosine (PIA, 10 microM). This action of PIA on mucosal cyclic AMP was antagonized by theophylline (1 mM) and was insensitive to tetrodotoxin (100 nM). The potency of PIA was 100-fold higher than that of 5'-N-ethylcarboxamido-adenosine (NECA). It is suggested that adenosine A1 receptors are present in rat jejunal mucosal cells.