Release of purines and noradrenaline by ouabain and potassium chloride from vascular adrenergic nerves.

1 Release of [3H]-noradrenaline and 3H-purine by ouabain (10(-4)M) or high KCl (50 mM) was investigated in the superfused rabbit pulmonary arterial segment preincubated with [3H]-noradrenaline or [3H]-adenosine. 2 Ouabain elicited a delayed large contraction and a parallel [3H]-noradrenaline efflux. These were substantially inhibited by Ca2+-free medium or preincubation with 6-hydroxydopamine (30 micrograms/ml, 30 min). 3 Ouabain caused an 3H-purine efflux which was slower than the [3H]-noradrenaline efflux. This was inhibited by 6-hydroxydopamine and in part by phentolamine (3 X 10(-6)M), indicating both neuronal and extraneuronal origins of purines. 4 In contrast to ouabain, high KCl appeared to induce predominantly purine efflux, which was phentolamine-insensitive and 6-hydroxydopamine-sensitive, indicative of neuronal origin. 5 It is suggested that the purine efflux evoked by ouabain and high KCl may originate from different neuronal vesicles.