Adenosine potentiates secretin-stimulated pancreatic exocrine secretion in the dog.

Pretreatment with graded doses of adenosine (0.1-1.0 mg), injected close-arterially (i.a.) to the vascularly isolated and self-hemoperfused dog pancreas, increased secretin (0.025 units i.a.)-stimulated secretory volume dose dependently and this effect of adenosine was reversed by further pretreatment with theophylline (0.3 mg i.a.). Adenosine itself did not affect the rate of resting secretion and the concentrations of protein and bicarbonate of the resting pancreatic juice. Adenosine decreased the concentration of protein and increased that of bicarbonate in the pancreatic juice stimulated by secretin. Adenosine, however, did not affect dopamine (3 micrograms i.a.)-stimulated pancreatic secretion. Adenosine (0.1-1.0 mg i.a.)-induced vasodilation was also reversed by the pretreatment with theophylline (0.3 mg i.a.). These results suggest the existence of adenosine 'R' receptors in the exocrine cells and the vasculature of the dog pancreas.