The steady-state concentration gradient for 3H-noradrenaline generated by uptake1 in the extracellular space of the rat vas deferens incubated with this amine.

The rat vas deferens was incubated with 0.2 μmol/l 3H-noradrenaline for 60 min, washed out with amine-free solution for 100 min and then prepared for autoradiography (same tissues as presented by Azevedo et al. (1990) Naunyn-Schmiedeberg's Arch Pharmacol 342: 245 – 248). The autoradiography images were then digitized, and grain density was determined as a function of the distance from the surface of the tissue. When neither monoamine oxidase nor vesicular uptake was impaired, i. e. under control conditions, grain density declined monophasically exponentially towards the centre of the tissue. This decline amounted to 0.017 μm−1 or 0.124 varicosity−1, since the average distance between varicosities was calculated to be 7.4 μm. After inhibition of monoamine oxidase and vesicular uptake the rate constant was significantly reduced, and the grain density in close proximity of the surface of the tissue was also reduced.