THE EFFECT OF VARIOUS SUBSTANCES ON THE EFFLUX OF LABELED CATECHOLAMINES FROM THE UTERUS OF THE RAT

¹ Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota

The efflux of labeled epinephrine and norepinephrine from immature uteri of rats was determined in vitro. The concentration of labeled amines decreased about 15 to 25% spontaneously. Various metabolic inhibitors and incubation at 0°C did not further increase efflux. The effiux of labeled catecholamines was increased in the presence of reserpine, d,l-norepinephrine or tyramine. The effect of the latter two agents but not that of reserpine was blocked by low temperature, fluoride or cocaine. The uptake of norepinephrine by the uterus was inhibited competitively by cocaine. Time results of this study indicate that tyramine and norepinephrine must be actively transported into the uterus in order to exchange with or to produce an effiux of tissue catecholamines.