A comparative study of the distribution of tritiated and endogenous noradrenaline in the rat vas deferens and in the dog spleen capsule

Summary The aim of the present work was to study the influence of tissue morphological characteristics on the neuronal release (and by inference the distribution) of tritiated and endogenous noradrenaline.Rat vas deferens and dog spleen capsule were loaded with 0.2 mol/l ³H-noradrenaline, after inhibition of the noradrenaline metabolizing enzymes. Some preparations were washed out under control conditions (spontaneous efflux) and others were washed out in the presence of the releasing agents: 40 mol/l of Ro 4-1284 (a reserpine-like compound), 100 mmol/l potassium or 100 mol/l tyramine. The fractional rate of loss (efflux/tissue content) of each amine was determined and the ratio endogenous amine/³H-noradrenaline in the efflux and in the tissue were also calculated. The results showed no preferential release of one of the amines in the spleen capsule, whereas a preferential release of tritiated noradrenaline was observed in the vas deferens. The smooth muscle layer in the vas deferens was much thicker and more compact than that of the spleen capsule. The ³H-sorbitol space was smaller in the former than in the latter.We conclude that the morphological characteristics of the tissues contribute to the differences in ³H-noradrenaline distribution in the adrenergic varicosities of these preparations.Supported by INIC, FmP1 Correspondence to: M. Q. Paiva at the above address