Possible selective inhibition of [3H]adenosine uptake by papaverine in vascular adrenergic nerves.

ABSTRACT

The effect of the adenosine uptake inhibitors dipyridamole, papaverine and diazepam on the [3H]adenosine uptake was assessed using the rabbit pulmonary arterial segment. [3H]Adenosine uptake into the vascular segment was significantly diminished by dipyridamole (10(-6) -10(-5) M), papaverine (10(-5) -10(-4) M) or diazepam (5 x 10(-5) M) with potencies dipyridamole greater than papaverine greater than diazepam. Dipyridamole (10(-6) M) or diazepam (5 x 10(-5) M) added 30 min before the incubation with [3H]adenosine reduced the high KCl-induced and epinephrine-induced [3H]purine effluxes equally, whereas papaverine (10(-5) M) selectively diminished the former efflux. KCl and epinephrine have been shown to act preferentially on the neuronal and extraneuronal sites, respectively. These results suggest that papaverine inhibits adenosine uptake into the vascular neuronal compartment, in preference to that into the extraneuronal compartment.