Active Transport of3H‐Bretylium in the Rat Vas Deferens in vitro

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Abstract
The uptake and efflux of3H‐bretylium in slices of the rat vas deferens were examined. The uptake of bretylium was temperature, Na+and Cl‐dependent, sensitive to 6‐hydroxydopamine but insensitive to reserpine. The uptake was inhibited by desipramine, (+)‐amphetamine, imipramine methiodide and cocaine, whereas the local anaesthetics millicaine and lidocaine were poor inhibitors. The spontaneous efflux was very slow at 0°C and slow at 37°. Desipramine accelerated the efflux probably by inhibiting the re‐uptake of bretylium. (+)‐Amphetamine, low external Na+, high external K+and ouabain caused a pronounced increase in the efflux at 37°C but was almost without effect at 0°C. The efflux evoked by (+)‐amphetamine, low Na+and ouabain was inhibited by desipramine, imipramine methiodide and cocaine, whereas millicaine and lidocaine had very poor effects. The increase of bretylium efflux by hypertonic K+was only slightly inhibited by desipramine and partially antagonized by omission of Ca2+in the medium. The results obtained indicate that bretylium was taken up in noradrenergic neurones by the noradrenaline transport mechanism and that the efflux of bretylium produced by (+)‐amphetamine, low external Na+, low external Cl‐and by ouabain occurred by the same transport mechanism as the uptake but now working in the outward direction whereas the efflux induced by high K+seemed to occur mainly with another mechanism.