The accumulation of adenosine in rabbit intestinal muscle.

1 Strips of longitudinal muscle from rabbit intestine accumulated radioactivity when exposed to [(3)H]-adenosine.2 Accumulation of radioactivity was not sodium-dependent or ouabain-sensitive, but was reduced by cooling, zero glucose plus bubbling with N(2), 2,4,dinitrophenol, dipyridamole, hexobendine and lidoflazine.3 After 7 min exposure to [(3)H]-adenosine, the tissue was found to contain radioactive adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and adenosine itself in the approximate ratio 13: 6: 4: 1.4 In the presence of dipyridamole, hexobendine or lidoflazine (each 1 muM), the amounts of radioactive ATP, ADP, AMP and adenosine were reduced with the concentration of adenosine not significantly different from controls.5 It is concluded that energy-dependent uptake of adenosine does not occur in the longitudinal muscle of rabbit intestine. Adenosine enters the tissue by a passive process and rapidly becomes phosphorylated giving rise to apparently high tissue: medium ratios.6 The drugs dipyridamole, hexobendine and lidoflazine appear to reduce the accumulation of radioactivity by preventing the formation of adenosine phosphate derivatives.