Effects of amiloride on contractions and the release of tritium from rat vas deferens preloaded with [3H]-noradrenaline.

1 The effect of amiloride was studied on contractions and tritium release from rat vas deferens preloaded with [3H]-noradrenaline. 2 Amiloride had no effect on the resting tension and maximal contractile force of the vas deferens and did not alter the ED50 of noradrenaline. 3 Amiloride (10(-4)-10(-3)M) decreased the response of vas deferens to electrical stimulation dose-dependently without inhibiting the response to KCI (60mM). 4 The effect of amiloride was not prevented by preincubation of the tissue with phentolamine, propranolol, atropine or indomethacin. 5 Amiloride did not alter the spontaneous outflow of radioactivity from [3H]-noradrenaline labelled vasa deferentia. 6 Amiloride decreased the release of tritium induced by electrical stimulation or nicotine but did not inhibit the release of radioactivity induced by KCI or tyramine. 7 It is concluded that amiloride may inhibit the contractions of rat vas deferens by inhibiting the release of noradrenaline.