Effects of calcium-removal and sodium-potassium adenosine triphosphatase inhibition on the release of epinephrine from the extraneuronal site.

Releases of unchanged epinephrine from the extraneuronal site of the isolated guinea-pig vas deferens were fluorimetrically determined by direct trihydroxyindole reaction at two different pH. The spontaneous release of the amine from the normal preparation preloaded with 3 x 10^?5 M epinephrine was significantly enhanced by inhibitions of Na-K ATPase or by Ca-removal. After epinephrine loading, the release of the amine from the preparation pretreated with pargyline and pyrogallol or from the denervated preparation was also enhanced by the both procedures. These enhanced releases of the amine were prevented by pretreatment of clonidine, Uptake 2 inhibitor, preceded the epinephrine loading. From these results, it was suspected that the retention or the release of the extraneuronal catecholamine in the vas deferens might be partly modified through the alteration of the Na-K ATPase activity and Ca concentration of the cell membrane.